##### Leader of the research group: Paweł Horodecki

Post-doc: Piotr Mironowicz, Borhan Ahmadi, Some Sankar Bhattacharya, Nitica Sakharwade, Tomasz Miller, Michał Banacki

PhD students: Ricard Ravell, Sumit Rout

The broad aim of the New Quantum Resources Group would be to perform research concerning quantum phenomena which could be used for quantum information processing.

## Activity

Examples of possible initial specific topics are:

– Connections between quantum computational speedup and contextuality/Bell-“nonlocality”

– New protocols on randomness amplification

– Research on communication networks

– Connections between violations of Bell inequalities and of non-contextuality and the quantum

advantage in communication complexity

– Quantum thermodynamics with state transitions by Thermal Operations.

– Relativistic quantum information processing

## Publications

### 2022

- Paweł Horodecki, Łukasz Rudnicki, and Karol ifmmode dotZelse Żfiyczkowski. Five Open Problems in Quantum Information Theory.
*PRX Quantum*, 3:010101, mar 2022. acknowledgment to ICTQT IRAP project included doi:10.1103/PRXQuantum.3.010101

[BibTeX] [Download PDF]`@article{PRXQuantum.3.010101, title = {Five Open Problems in Quantum Information Theory}, author = {Horodecki, Pawe\l{} and Rudnicki, \L{}ukasz and \ifmmode \dot{Z}\else \.{Z}\fi{}yczkowski, Karol}, journal = {PRX Quantum}, volume = {3}, issue = {1}, pages = {010101}, numpages = {17}, year = {2022}, month = mar, publisher = {American Physical Society}, doi = {10.1103/PRXQuantum.3.010101}, url = {https://link.aps.org/doi/10.1103/PRXQuantum.3.010101}, note = {acknowledgment to ICTQT IRAP project included} }`

- Michał Banacki, Piotr Mironowicz, Ravishankar Ramanathan, and Paweł Horodecki. Hybrid no-signaling-quantum correlations.
*New Journal of Physics*, 24(8):083003, aug 2022. acknowledgement for ICTQT IRAP included doi:10.1088/1367-2630/ac7fb3

[BibTeX] [Abstract] [Download PDF]

Fundamental investigations in non-locality have shown that while the no-signaling principle alone is not sufficient to single out the set of quantum non-local correlations, local quantum mechanics and no-signaling together exactly reproduce the set of quantum correlations in the two-party Bell scenario. Here, we introduce and study an intermediate hybrid no-signaling quantum set of non-local correlations that we term \textbfHNSQ in the multi-party Bell scenario where some subsystems are locally quantum while the remaining subsystems are only constrained by the no-signaling principle. Specifically, the set \textbfHNSQ is a super-quantum set of correlations derived from no-signaling assemblages by performing quantum measurements on the trusted subsystems. We show that in contrast to the set \textbfNS of no-signaling behaviors, there exist extreme points of \textbfHNSQ in the tripartite Bell scenario that admit quantum realization. As a tool for optimization over the set \textbfHNSQ, we introduce an outer hierarchy of semi-definite programming approximations to the set following an approach put forward by Doherty–Parrilo–Spedalieri. We perform an extensive numerical analysis of the maximal violation of the facet Bell inequalities in the three-party binary input–output scenario and study the corresponding self-testing properties. In contrast to the usual no-signaling correlations, the new set allows for simple security proofs of (one-sided)-device-independent applications against super-quantum adversaries.

`@Article{banacki_hybrid_2022, author = {Banacki, Michał and Mironowicz, Piotr and Ramanathan, Ravishankar and Horodecki, Paweł}, journal = {New Journal of Physics}, title = {Hybrid no-signaling-quantum correlations}, note = {acknowledgement for ICTQT IRAP included}, year = {2022}, month = aug, number = {8}, pages = {083003}, volume = {24}, abstract = {Fundamental investigations in non-locality have shown that while the no-signaling principle alone is not sufficient to single out the set of quantum non-local correlations, local quantum mechanics and no-signaling together exactly reproduce the set of quantum correlations in the two-party Bell scenario. Here, we introduce and study an intermediate hybrid no-signaling quantum set of non-local correlations that we term \textbf{HNSQ} in the multi-party Bell scenario where some subsystems are locally quantum while the remaining subsystems are only constrained by the no-signaling principle. Specifically, the set \textbf{HNSQ} is a super-quantum set of correlations derived from no-signaling assemblages by performing quantum measurements on the trusted subsystems. We show that in contrast to the set \textbf{NS} of no-signaling behaviors, there exist extreme points of \textbf{HNSQ} in the tripartite Bell scenario that admit quantum realization. As a tool for optimization over the set \textbf{HNSQ}, we introduce an outer hierarchy of semi-definite programming approximations to the set following an approach put forward by Doherty–Parrilo–Spedalieri. We perform an extensive numerical analysis of the maximal violation of the facet Bell inequalities in the three-party binary input–output scenario and study the corresponding self-testing properties. In contrast to the usual no-signaling correlations, the new set allows for simple security proofs of (one-sided)-device-independent applications against super-quantum adversaries.}, groups = {Pawel_H}, doi = {10.1088/1367-2630/ac7fb3}, keywords = {Quantum Physics}, url = {https://iopscience.iop.org/article/10.1088/1367-2630/ac7fb3}, }`

- Michał Eckstein and Paweł Horodecki. Probing the limits of quantum theory with quantum information at subnuclear scales.
*Proc. R. Soc. A.*, 478:20210806, mar 2022. acknowledgement for ICTQT IRAP included doi:10.1098/rspa.2021.0806

[BibTeX] [Abstract] [Download PDF]

Modern quantum engineering techniques enabled successful foundational tests of quantum mechanics. Yet, the universal validity of quantum postulates is an open question. Here we propose a new theoretical framework of Q-data tests, which recognizes the established validity of quantum theory, but allows for more general—‘post-quantum’—scenarios in certain physical regimes. It can accommodate a large class of models with modified quantum wave dynamics, correlations beyond entanglement or general probabilistic postulates. We discuss its experimental implementation suited to probe the nature of strong nuclear interactions. In contrast to the present accelerator experiments, it shifts the focus from high-luminosity beam physics to individual particle coherent control.

`@article{Eckstein_probing_2022, doi = {10.1098/rspa.2021.0806}, url = {https://royalsocietypublishing.org/doi/abs/10.1098/rspa.2021.0806}, year = 2022, month = mar, volume = {478}, pages = {20210806}, author = {Eckstein, Micha{\l} and Horodecki, Pawe{\l}}, title = {Probing the limits of quantum theory with quantum information at subnuclear scales}, note= {acknowledgement for ICTQT IRAP included}, journal = {Proc. R. Soc. A.}, abstract = {Modern quantum engineering techniques enabled successful foundational tests of quantum mechanics. Yet, the universal validity of quantum postulates is an open question. Here we propose a new theoretical framework of Q-data tests, which recognizes the established validity of quantum theory, but allows for more general—‘post-quantum’—scenarios in certain physical regimes. It can accommodate a large class of models with modified quantum wave dynamics, correlations beyond entanglement or general probabilistic postulates. We discuss its experimental implementation suited to probe the nature of strong nuclear interactions. In contrast to the present accelerator experiments, it shifts the focus from high-luminosity beam physics to individual particle coherent control.}, groups = {Pawel_H}, }`

- Erik Aurell, Michał Eckstein, and Paweł Horodecki. Hawking radiation and the quantum marginal problem.
*Journal of Cosmology and Astroparticle Physics*, 2022(01):014, jan 2022. acknowledgement for ICTQT IRAP included doi:10.1088/1475-7516/2022/01/014

[BibTeX] [Abstract] [Download PDF]

In 1974 Steven Hawking showed that black holes emit thermal radiation, which eventually causes them to evaporate. The problem of the fate of information in this process is known as the “black hole information paradox”. Two main types of resolution postulate either a fundamental loss of information in Nature — hence the breakdown of quantum mechanics — or some sort of new physics, e.g. quantum gravity, which guarantee the global preservation of unitarity. Here we explore the second possibility with the help of recent developments in continuous-variable quantum information. Concretely, we employ the solution to the Gaussian quantum marginal problem to show that the thermality of all individual Hawking modes is consistent with a global pure state of the radiation. Surprisingly, we find out that the mods of radiation of an astrophysical black hole are thermal until the very last burst. In contrast, the single-mode thermality of Hawking radiation originating from microscopic black holes, expected to evaporate through several quanta, is not excluded, though there are constraints on modes’ frequencies. Our result paves the way towards a systematic study of multi-mode correlations in Hawking radiation.

`@article{Aurell__hawking_2022, doi = {10.1088/1475-7516/2022/01/014}, url = {https://doi.org/10.1088/1475-7516/2022/01/014}, year = 2022, month = jan, publisher = {{IOP} Publishing}, volume = {2022}, number = {01}, pages = {014}, author = {Aurell, Erik and Eckstein, Micha{\l} and Horodecki, Pawe{\l}}, title = {Hawking radiation and the quantum marginal problem}, note= {acknowledgement for ICTQT IRAP included}, journal = {Journal of Cosmology and Astroparticle Physics}, abstract = {In 1974 Steven Hawking showed that black holes emit thermal radiation, which eventually causes them to evaporate. The problem of the fate of information in this process is known as the “black hole information paradox”. Two main types of resolution postulate either a fundamental loss of information in Nature — hence the breakdown of quantum mechanics — or some sort of new physics, e.g. quantum gravity, which guarantee the global preservation of unitarity. Here we explore the second possibility with the help of recent developments in continuous-variable quantum information. Concretely, we employ the solution to the Gaussian quantum marginal problem to show that the thermality of all individual Hawking modes is consistent with a global pure state of the radiation. Surprisingly, we find out that the mods of radiation of an astrophysical black hole are thermal until the very last burst. In contrast, the single-mode thermality of Hawking radiation originating from microscopic black holes, expected to evaporate through several quanta, is not excluded, though there are constraints on modes' frequencies. Our result paves the way towards a systematic study of multi-mode correlations in Hawking radiation.}, groups = {Pawel_H}, }`

- Piotr Mironowicz, Paweł Horodecki, and Ryszard Horodecki. Non-Perfect Propagation of Information to a Noisy Environment with Self-Evolution.
*Entropy*, 24(4), mar 2022. acknowledgement for ICTQT IRAP included doi:10.3390/e24040467

[BibTeX] [Abstract] [Download PDF]

We study the non-perfect propagation of information for evolving a low-dimensional environment that includes self-evolution as well as noisy initial states and analyse the interrelations between the degree of objectivization and environment parameters. In particular, we consider an analytical model of three interacting qubits and derive its objectivity parameters. The numerical analysis shows that the quality of the spectrum broadcast structure formed during the interaction may exhibit non-monotonicity both in the speed of self-dynamics of the environment as well as its mixedness. The former effect is particularly strong, showing that—considering part of the environment as a measurement apparatus—an increase of the external magnetic field acting on the environment may turn the vague measurement into close to ideal. The above effects suggest that quantum objectivity may appear after increasing the dynamics of the environment, although not with respect to the pointer basis, but some other, which we call the generalized pointer or indicator basis. Furthermore, it seems also that, when the objectivity is poor, it may be improved, at least by some amount, by increasing the thermal noise. We provide further evidence of this by analysing the upper bounds on distance to the set of states representing perfect objectivity in the case of a higher number of qubits.

`@article{Mironowicz_non-perfect_2022, author = {Mironowicz, Piotr and Horodecki, Paweł and Horodecki, Ryszard}, title = {Non-Perfect Propagation of Information to a Noisy Environment with Self-Evolution}, note= {acknowledgement for ICTQT IRAP included}, journal = {Entropy}, volume = {24}, year = {2022}, month = mar, number = {4}, article-number = {467}, url = {https://www.mdpi.com/1099-4300/24/4/467}, PubMedID = {35455130}, ISSN = {1099-4300}, abstract = {We study the non-perfect propagation of information for evolving a low-dimensional environment that includes self-evolution as well as noisy initial states and analyse the interrelations between the degree of objectivization and environment parameters. In particular, we consider an analytical model of three interacting qubits and derive its objectivity parameters. The numerical analysis shows that the quality of the spectrum broadcast structure formed during the interaction may exhibit non-monotonicity both in the speed of self-dynamics of the environment as well as its mixedness. The former effect is particularly strong, showing that—considering part of the environment as a measurement apparatus—an increase of the external magnetic field acting on the environment may turn the vague measurement into close to ideal. The above effects suggest that quantum objectivity may appear after increasing the dynamics of the environment, although not with respect to the pointer basis, but some other, which we call the generalized pointer or indicator basis. Furthermore, it seems also that, when the objectivity is poor, it may be improved, at least by some amount, by increasing the thermal noise. We provide further evidence of this by analysing the upper bounds on distance to the set of states representing perfect objectivity in the case of a higher number of qubits.}, groups = {Pawel_H}, doi = {10.3390/e24040467}, }`

- Ravishankar Ramanathan, Yuan Liu, and Paweł Horodecki. *Large violations in Kochen Specker contextuality and their applications.
*New Journal of Physics*, 24(3):033035, mar 2022. doi:10.1088/1367-2630/ac3a84

[BibTeX] [Download PDF]`@article{Ramanathan_large_2022, title = {*Large violations in Kochen Specker contextuality and their applications}, author = {Ramanathan, Ravishankar and Liu, Yuan and Horodecki, Pawe\l{}}, journal = {New Journal of Physics}, volume = {24}, number = {3}, pages = {033035}, year = {2022}, month = mar, groups = {Pawel_H}, doi = {10.1088/1367-2630/ac3a84}, url = {https://iopscience.iop.org/article/10.1088/1367-2630/ac3a84}, }`

- Sahil Gopalkrishna Naik, Edwin Peter Lobo, Samrat Sen, Ram Krishna Patra, Mir Alimuddin, Tamal Guha, Some Sankar Bhattacharya, and Manik Banik. Composition of Multipartite Quantum Systems: Perspective from Timelike Paradigm.
*Phys. Rev. Lett.*, 128:140401, apr 2022. acknowledgement for ICTQT IRAP included doi:10.1103/PhysRevLett.128.140401

[BibTeX] [Abstract] [Download PDF]

Figuring out the physical rationale behind natural selection of quantum theory is one of the most acclaimed quests in quantum foundational research. This pursuit has inspired several axiomatic initiatives to derive a mathematical formulation of the theory by identifying the general structure of state and effect space of individual systems as well as specifying their composition rules. This generic framework can allow several consistent composition rules for a multipartite system even when state and effect cones of individual subsystems are assumed to be quantum. Nevertheless, for any bipartite system, none of these compositions allows beyond quantum spacelike correlations. In this Letter, we show that such bipartite compositions can admit stronger-than-quantum correlations in the timelike domain and, hence, indicates pragmatically distinct roles carried out by state and effect cones. We discuss consequences of such correlations in a communication task, which accordingly opens up a possibility of testing the actual composition between elementary quanta.

`@article{Naik_composition_2022, title = {Composition of Multipartite Quantum Systems: Perspective from Timelike Paradigm}, author = {Naik, Sahil Gopalkrishna and Lobo, Edwin Peter and Sen, Samrat and Patra, Ram Krishna and Alimuddin, Mir and Guha, Tamal and Bhattacharya, Some Sankar and Banik, Manik}, note= {acknowledgement for ICTQT IRAP included}, journal = {Phys. Rev. Lett.}, volume = {128}, issue = {14}, pages = {140401}, numpages = {7}, year = {2022}, month = apr, abstract={Figuring out the physical rationale behind natural selection of quantum theory is one of the most acclaimed quests in quantum foundational research. This pursuit has inspired several axiomatic initiatives to derive a mathematical formulation of the theory by identifying the general structure of state and effect space of individual systems as well as specifying their composition rules. This generic framework can allow several consistent composition rules for a multipartite system even when state and effect cones of individual subsystems are assumed to be quantum. Nevertheless, for any bipartite system, none of these compositions allows beyond quantum spacelike correlations. In this Letter, we show that such bipartite compositions can admit stronger-than-quantum correlations in the timelike domain and, hence, indicates pragmatically distinct roles carried out by state and effect cones. We discuss consequences of such correlations in a communication task, which accordingly opens up a possibility of testing the actual composition between elementary quanta.}, publisher = {American Physical Society}, groups = {Pawel_H}, doi = {10.1103/PhysRevLett.128.140401}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.128.140401}, }`

- Samrat Sen, Edwin Peter Lobo, Sahil Gopalkrishna Naik, Ram Krishna Patra, Tathagata Gupta, Subhendu B. Ghosh, Sutapa Saha, Mir Alimuddin, Tamal Guha, Some Sankar Bhattacharya, and Manik Banik. Local quantum state marking.
*Phys. Rev. A*, 105:032407, mar 2022. acknowledgement for ICTQT IRAP included doi:10.1103/PhysRevA.105.032407

[BibTeX] [Abstract] [Download PDF]

We propose the task of local state marking (LSM), where some multipartite quantum states chosen randomly from a known set of states are distributed among spatially separated parties without revealing the identities of the individual states. The collaborative aim of the parties is to correctly mark the identities of states under the restriction that they can perform only local quantum operations (LOs) on their respective subsystems and can communicate with each other classically (CC)—popularly known as the operational paradigm of LOCC. While mutually orthogonal states can always be marked exactly under global operations, this is in general not the case under LOCC. We show that the LSM task is distinct from the vastly explored task of local state distinguishability (LSD)—perfect LSD always implies perfect LSM, whereas we establish that the converse does not hold in general. We also explore entanglement-assisted marking of states that are otherwise locally unmarkable, and we report intriguing entanglement-assisted catalytic LSM phenomena.

`@article{Sen_local_2022, title = {Local quantum state marking}, author = {Sen, Samrat and Lobo, Edwin Peter and Naik, Sahil Gopalkrishna and Patra, Ram Krishna and Gupta, Tathagata and Ghosh, Subhendu B. and Saha, Sutapa and Alimuddin, Mir and Guha, Tamal and Bhattacharya, Some Sankar and Banik, Manik}, note= {acknowledgement for ICTQT IRAP included}, journal = {Phys. Rev. A}, volume = {105}, issue = {3}, pages = {032407}, numpages = {10}, year = {2022}, month = mar, abstract={We propose the task of local state marking (LSM), where some multipartite quantum states chosen randomly from a known set of states are distributed among spatially separated parties without revealing the identities of the individual states. The collaborative aim of the parties is to correctly mark the identities of states under the restriction that they can perform only local quantum operations (LOs) on their respective subsystems and can communicate with each other classically (CC)—popularly known as the operational paradigm of LOCC. While mutually orthogonal states can always be marked exactly under global operations, this is in general not the case under LOCC. We show that the LSM task is distinct from the vastly explored task of local state distinguishability (LSD)—perfect LSD always implies perfect LSM, whereas we establish that the converse does not hold in general. We also explore entanglement-assisted marking of states that are otherwise locally unmarkable, and we report intriguing entanglement-assisted catalytic LSM phenomena.}, publisher = {American Physical Society}, groups = {Pawel_H}, doi = {10.1103/PhysRevA.105.032407}, url = {https://link.aps.org/doi/10.1103/PhysRevA.105.032407}, }`

### 2021

- Tomasz Miller, Michał Eckstein, Paweł Horodecki, and Ryszard Horodecki. Generally covariant N -particle dynamics.
*Journal of Geometry and Physics*, 160:103990, feb 2021. doi:10.1016/j.geomphys.2020.103990

[BibTeX] [Download PDF]`@Article{miller_generally_2021, author = {Miller, Tomasz and Eckstein, Michał and Horodecki, Paweł and Horodecki, Ryszard}, journal = {Journal of {G}eometry and {P}hysics}, title = {Generally covariant {N} -particle dynamics}, year = {2021}, issn = {03930440}, month = feb, pages = {103990}, volume = {160}, doi = {10.1016/j.geomphys.2020.103990}, groups = {Pawel_H, Michal_H}, language = {en}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0393044020302539}, urldate = {2021-05-10}, }`

- B. Ahmadi, S. Salimi, and A. S. Khorashad. Irreversible work and Maxwell demon in terms of quantum thermodynamic force.
*Scientific Reports*, 11(1):2301, dec 2021. doi:10.1038/s41598-021-81737-z

[BibTeX] [Abstract] [Download PDF]

Abstract The second law of classical equilibrium thermodynamics, based on the positivity of entropy production, asserts that any process occurs only in a direction that some information may be lost (flow out of the system) due to the irreversibility inside the system. However, any thermodynamic system can exhibit fluctuations in which negative entropy production may be observed. In particular, in stochastic quantum processes due to quantum correlations and also memory effects we may see the reversal energy flow (heat flow from the cold system to the hot system) and the backflow of information into the system that leads to the negativity of the entropy production which is an apparent violation of the Second Law. In order to resolve this apparent violation, we will try to properly extend the Second Law to quantum processes by incorporating information explicitly into the Second Law. We will also provide a thermodynamic operational meaning for the flow and backflow of information. Finally, it is shown that negative and positive entropy production can be described by a quantum thermodynamic force.

`@Article{ahmadi_irreversible_2021, author = {Ahmadi, B. and Salimi, S. and Khorashad, A. S.}, journal = {Scientific {R}eports}, title = {Irreversible work and {Maxwell} demon in terms of quantum thermodynamic force}, year = {2021}, issn = {2045-2322}, month = dec, number = {1}, pages = {2301}, volume = {11}, abstract = {Abstract The second law of classical equilibrium thermodynamics, based on the positivity of entropy production, asserts that any process occurs only in a direction that some information may be lost (flow out of the system) due to the irreversibility inside the system. However, any thermodynamic system can exhibit fluctuations in which negative entropy production may be observed. In particular, in stochastic quantum processes due to quantum correlations and also memory effects we may see the reversal energy flow (heat flow from the cold system to the hot system) and the backflow of information into the system that leads to the negativity of the entropy production which is an apparent violation of the Second Law. In order to resolve this apparent violation, we will try to properly extend the Second Law to quantum processes by incorporating information explicitly into the Second Law. We will also provide a thermodynamic operational meaning for the flow and backflow of information. Finally, it is shown that negative and positive entropy production can be described by a quantum thermodynamic force.}, doi = {10.1038/s41598-021-81737-z}, language = {en}, url = {http://www.nature.com/articles/s41598-021-81737-z}, urldate = {2021-05-10}, }`

- Piotr Mironowicz, Gustavo Cañas, Jaime Cariñe, Esteban S. Gómez, Johanna F. Barra, Adán Cabello, Guilherme B. Xavier, Gustavo Lima, and Marcin Pawłowski. Quantum randomness protected against detection loophole attacks.
*Quantum Information Processing*, 20(1):39, jan 2021. doi:10.1007/s11128-020-02948-3

[BibTeX] [Download PDF]`@Article{mironowicz_quantum_2021, author = {Mironowicz, Piotr and Cañas, Gustavo and Cariñe, Jaime and Gómez, Esteban S. and Barra, Johanna F. and Cabello, Adán and Xavier, Guilherme B. and Lima, Gustavo and Pawłowski, Marcin}, journal = {Quantum {I}nformation {P}rocessing}, title = {Quantum randomness protected against detection loophole attacks}, year = {2021}, issn = {1570-0755, 1573-1332}, month = jan, number = {1}, pages = {39}, volume = {20}, doi = {10.1007/s11128-020-02948-3}, language = {en}, url = {http://link.springer.com/10.1007/s11128-020-02948-3}, urldate = {2021-05-10}, }`

- Roberto Salazar, Tanmoy Biswas, Jakub Czartowski, Karol Życzkowski, and Paweł Horodecki. Optimal allocation of quantum resources.
*Quantum*, 5:407, mar 2021. doi:10.22331/q-2021-03-10-407

[BibTeX] [Abstract] [Download PDF]

The optimal allocation of resources is a crucial task for their efficient use in a wide range of practical applications in science and engineering. This paper investigates the optimal allocation of resources in multipartite quantum systems. In particular, we show the relevance of proportional fairness and optimal reliability criteria for the application of quantum resources. Moreover, we present optimal allocation solutions for an arbitrary number of qudits using measurement incompatibility as an exemplary resource theory. Besides, we study the criterion of optimal equitability and demonstrate its relevance to scenarios involving several resource theories such as nonlocality vs local contextuality. Finally, we highlight the potential impact of our results for quantum networks and other multi-party quantum information processing, in particular to the future Quantum Internet.

`@Article{salazar_optimal_2021, author = {Salazar, Roberto and Biswas, Tanmoy and Czartowski, Jakub and Życzkowski, Karol and Horodecki, Paweł}, journal = {Quantum}, title = {Optimal allocation of quantum resources}, year = {2021}, issn = {2521-327X}, month = mar, pages = {407}, volume = {5}, abstract = {The optimal allocation of resources is a crucial task for their efficient use in a wide range of practical applications in science and engineering. This paper investigates the optimal allocation of resources in multipartite quantum systems. In particular, we show the relevance of proportional fairness and optimal reliability criteria for the application of quantum resources. Moreover, we present optimal allocation solutions for an arbitrary number of qudits using measurement incompatibility as an exemplary resource theory. Besides, we study the criterion of optimal equitability and demonstrate its relevance to scenarios involving several resource theories such as nonlocality vs local contextuality. Finally, we highlight the potential impact of our results for quantum networks and other multi-party quantum information processing, in particular to the future Quantum Internet.}, doi = {10.22331/q-2021-03-10-407}, groups = {Pawel_H}, language = {en}, url = {https://quantum-journal.org/papers/q-2021-03-10-407/}, urldate = {2021-07-28}, }`

- Michał Banacki, Ricard Ravell Rodríguez, and Paweł Horodecki. On the edge of the set of no-signaling assemblages.
*Physical Review A*, 103(5):052434, may 2021. arXiv: 2008.12325 doi:10.1103/PhysRevA.103.052434

[BibTeX] [Abstract] [Download PDF]

Following recent advancements, we consider a scenario of multipartite postquantum steering and general no-signaling assemblages. We introduce the notion of the edge of the set of no-signaling assemblages and we present its characterization. Next, we use this concept to construct witnesses for no-signaling assemblages without an LHS model. Finally, in the simplest nontrivial case of steering with two untrusted subsystems, we discuss the possibility of quantum realization of assemblages on the edge. In particular, for three-qubit states, we obtain a no-go type result, which states that it is impossible to produce assemblage on the edge using measurements described by POVMs as long as the rank of a given state is greater than or equal to 3.

`@Article{banacki_edge_2021, author = {Banacki, Michał and Rodríguez, Ricard Ravell and Horodecki, Paweł}, journal = {Physical {R}eview {A}}, title = {On the edge of the set of no-signaling assemblages}, year = {2021}, issn = {2469-9926, 2469-9934}, month = may, note = {arXiv: 2008.12325}, number = {5}, pages = {052434}, volume = {103}, abstract = {Following recent advancements, we consider a scenario of multipartite postquantum steering and general no-signaling assemblages. We introduce the notion of the edge of the set of no-signaling assemblages and we present its characterization. Next, we use this concept to construct witnesses for no-signaling assemblages without an LHS model. Finally, in the simplest nontrivial case of steering with two untrusted subsystems, we discuss the possibility of quantum realization of assemblages on the edge. In particular, for three-qubit states, we obtain a no-go type result, which states that it is impossible to produce assemblage on the edge using measurements described by POVMs as long as the rank of a given state is greater than or equal to 3.}, doi = {10.1103/PhysRevA.103.052434}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/2008.12325}, urldate = {2021-07-28}, }`

- Erik Aurell, Michał Eckstein, and Paweł Horodecki. Quantum Black Holes as Solvents.
*Foundations of Physics*, 51(2):54, apr 2021. doi:10.1007/s10701-021-00456-7

[BibTeX] [Abstract] [Download PDF]

Abstract Almost all of the entropy in the universe is in the form of Bekenstein–Hawking (BH) entropy of super-massive black holes. This entropy, if it satisfies Boltzmann’s equation \$\$S=\textbackslashlog \textbackslashmathcal\N\\$\$ S = log N , hence represents almost all the accessible phase space of the Universe, somehow associated to objects which themselves fill out a very small fraction of ordinary three-dimensional space. Although time scales are very long, it is believed that black holes will eventually evaporate by emitting Hawking radiation, which is thermal when counted mode by mode. A pure quantum state collapsing to a black hole will hence eventually re-emerge as a state with strictly positive entropy, which constitutes the famous black hole information paradox. Expanding on a remark by Hawking we posit that BH entropy is a thermodynamic entropy, which must be distinguished from information-theoretic entropy. The paradox can then be explained by information return in Hawking radiation. The novel perspective advanced here is that if BH entropy counts the number of accessible physical states in a quantum black hole, then the paradox can be seen as an instance of the fundamental problem of statistical mechanics. We suggest a specific analogy to the increase of the entropy in a solvation process. We further show that the huge phase volume ( \$\$\textbackslashmathcal\N\\$\$ N ), which must be made available to the universe in a gravitational collapse, cannot originate from the entanglement between ordinary matter and/or radiation inside and outside the black hole. We argue that, instead, the quantum degrees of freedom of the gravitational field must get activated near the singularity, resulting in a final state of the ‘entangled entanglement’ form involving both matter and gravity.

`@Article{Aurell2021, author = {Aurell, Erik and Eckstein, Michał and Horodecki, Paweł}, journal = {Foundations of {P}hysics}, title = {Quantum {Black} {Holes} as {Solvents}}, year = {2021}, issn = {0015-9018, 1572-9516}, month = apr, number = {2}, pages = {54}, volume = {51}, abstract = {Abstract Almost all of the entropy in the universe is in the form of Bekenstein–Hawking (BH) entropy of super-massive black holes. This entropy, if it satisfies Boltzmann’s equation \$\$S={\textbackslash}log {\textbackslash}mathcal\{N\}\$\$ S = log N , hence represents almost all the accessible phase space of the Universe, somehow associated to objects which themselves fill out a very small fraction of ordinary three-dimensional space. Although time scales are very long, it is believed that black holes will eventually evaporate by emitting Hawking radiation, which is thermal when counted mode by mode. A pure quantum state collapsing to a black hole will hence eventually re-emerge as a state with strictly positive entropy, which constitutes the famous black hole information paradox. Expanding on a remark by Hawking we posit that BH entropy is a thermodynamic entropy, which must be distinguished from information-theoretic entropy. The paradox can then be explained by information return in Hawking radiation. The novel perspective advanced here is that if BH entropy counts the number of accessible physical states in a quantum black hole, then the paradox can be seen as an instance of the fundamental problem of statistical mechanics. We suggest a specific analogy to the increase of the entropy in a solvation process. We further show that the huge phase volume ( \$\${\textbackslash}mathcal\{N\}\$\$ N ), which must be made available to the universe in a gravitational collapse, cannot originate from the entanglement between ordinary matter and/or radiation inside and outside the black hole. We argue that, instead, the quantum degrees of freedom of the gravitational field must get activated near the singularity, resulting in a final state of the ‘entangled entanglement’ form involving both matter and gravity.}, doi = {10.1007/s10701-021-00456-7}, groups = {Pawel_H}, language = {en}, url = {https://link.springer.com/10.1007/s10701-021-00456-7}, urldate = {2021-10-11}, }`

- Carlo Maria Scandolo, Roberto Salazar, Jarosław K. Korbicz, and Paweł Horodecki. Universal structure of objective states in all fundamental causal theories.
*Physical Review Research*, 3(3):033148, aug 2021. doi:10.1103/PhysRevResearch.3.033148

[BibTeX] [Abstract] [Download PDF]

A crucial question is how objective and classical behavior arises from a fundamental physical theory. Here we provide a natural definition of a decoherence process valid in all causal theories and show how its behavior can be extremely different from the quantum one. Remarkably, despite this, we prove that the so- called spectrum broadcast structure characterizes all objective states in every fundamental causal theory, exactly as in quantum mechanics. Our results show a stark contrast between the extraordinarily diverse decoherence behavior and the universal features of objectivity.

`@Article{Scandolo2021, author = {Scandolo, Carlo Maria and Salazar, Roberto and Korbicz, Jarosław K. and Horodecki, Paweł}, journal = {Physical {R}eview {R}esearch}, title = {Universal structure of objective states in all fundamental causal theories}, year = {2021}, month = aug, number = {3}, pages = {033148}, volume = {3}, abstract = {A crucial question is how objective and classical behavior arises from a fundamental physical theory. Here we provide a natural definition of a decoherence process valid in all causal theories and show how its behavior can be extremely different from the quantum one. Remarkably, despite this, we prove that the so- called spectrum broadcast structure characterizes all objective states in every fundamental causal theory, exactly as in quantum mechanics. Our results show a stark contrast between the extraordinarily diverse decoherence behavior and the universal features of objectivity.}, doi = {10.1103/PhysRevResearch.3.033148}, eid = {033148}, groups = {Pawel_H}, url = {https://ui.adsabs.harvard.edu/abs/2021PhRvR...3c3148S}, }`

- Tamal Guha, Mir Alimuddin, Sumit Rout, Amit Mukherjee, Some Sankar Bhattacharya, and Manik Banik. Quantum Advantage for Shared Randomness Generation.
*Quantum*, 5:569, 2021. acknowledgement for ICTQT IRAP included doi:10.22331/q-2021-10-27-569

[BibTeX] [Download PDF]`@Article{Guha2021, author = {Guha, Tamal and Alimuddin, Mir and Rout, Sumit and Mukherjee, Amit and Bhattacharya, Some Sankar and Banik, Manik}, journal = {Quantum}, title = {Quantum Advantage for Shared Randomness Generation}, note= {acknowledgement for ICTQT IRAP included}, year = {2021}, pages = {569}, volume = {5}, archiveprefix = {arXiv}, doi = {10.22331/q-2021-10-27-569}, eprint = {2001.01889}, primaryclass = {quant-ph}, url = {https://quantum-journal.org/papers/q-2021-10-27-569/pdf/}, doi={10.22331/q-2021-10-27-569}, }`

- Zbigniew Puchała, Kamil Korzekwa, Roberto Salazar, Paweł Horodecki, and Karol ifmmode dotZelse Żfiyczkowski. Dephasing superchannels.
*Phys. Rev. A*, 104:052611, nov 2021. acknowledgement for ICTQT IRAP included doi:10.1103/PhysRevA.104.052611

[BibTeX] [Download PDF]`@article{puchala_dephasing_2021, author = {Pucha\l{}a, Zbigniew and Korzekwa, Kamil and Salazar, Roberto and Horodecki, Pawe\l{} and \ifmmode \dot{Z}\else \.{Z}\fi{}yczkowski, Karol}, title = {Dephasing superchannels}, note = {acknowledgement for ICTQT IRAP included}, journal = {Phys. Rev. A}, volume = {104}, issue = {5}, pages = {052611}, numpages = {12}, year = {2021}, month = nov, publisher = {American Physical Society}, groups = {Pawel_H}, doi = {10.1103/PhysRevA.104.052611}, url = {https://link.aps.org/doi/10.1103/PhysRevA.104.052611}, }`

- Sumit Rout, Ananda G. Maity, Amit Mukherjee, Saronath Halder, and Manik Banik. Multiparty orthogonal product states with minimal genuine nonlocality.
*Phys. Rev. A*, 104:052433, nov 2021. acknowledgement for ICTQT IRAP included doi:10.1103/PhysRevA.104.052433

[BibTeX] [Abstract] [Download PDF]

Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. The concept of a genuinely nonlocal set of product states emerges as a natural multipartite generalization of this phenomenon. The existence of such sets eventually raises the problem concerning their entanglement-assisted discrimination. Here, we construct examples of genuinely nonlocal product states for an arbitrary number of parties. The strength of genuine nonlocality of these sets can be considered minimal as their perfect discrimination is possible with entangled resources residing in Hilbert spaces having the smallest possible dimensions. Our constructions lead to fully separable measurements that are impossible to implement even if all but one party come together. Furthermore, they also provide the opportunity to compare different multipartite states that otherwise are incomparable under single copy local manipulation.

`@article{Sen_multiparty_2021, title = {Multiparty orthogonal product states with minimal genuine nonlocality}, author = {Rout, Sumit and Maity, Ananda G. and Mukherjee, Amit and Halder, Saronath and Banik, Manik}, journal = {Phys. Rev. A}, note= {acknowledgement for ICTQT IRAP included}, volume = {104}, issue = {5}, pages = {052433}, numpages = {8}, year = {2021}, month = nov, abstract={Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. The concept of a genuinely nonlocal set of product states emerges as a natural multipartite generalization of this phenomenon. The existence of such sets eventually raises the problem concerning their entanglement-assisted discrimination. Here, we construct examples of genuinely nonlocal product states for an arbitrary number of parties. The strength of genuine nonlocality of these sets can be considered minimal as their perfect discrimination is possible with entangled resources residing in Hilbert spaces having the smallest possible dimensions. Our constructions lead to fully separable measurements that are impossible to implement even if all but one party come together. Furthermore, they also provide the opportunity to compare different multipartite states that otherwise are incomparable under single copy local manipulation.}, publisher = {American Physical Society}, groups = {Pawel_H}, doi = {10.1103/PhysRevA.104.052433}, url = {https://link.aps.org/doi/10.1103/PhysRevA.104.052433}, }`

### 2020

- Massimiliano Smania, Piotr Mironowicz, Mohamed Nawareg, Marcin Pawłowski, Adán Cabello, and Mohamed Bourennane. Experimental certification of an informationally complete quantum measurement in a device-independent protocol.
*Optica*, 7(2):123, feb 2020. doi:10.1364/OPTICA.377959

[BibTeX] [Download PDF]`@article{smania_experimental_2020, title = {Experimental certification of an informationally complete quantum measurement in a device-independent protocol}, volume = {7}, issn = {2334-2536}, url = {https://www.osapublishing.org/abstract.cfm?URI=optica-7-2-123}, doi = {10.1364/OPTICA.377959}, language = {en}, number = {2}, urldate = {2020-04-22}, journal = {Optica}, author = {Smania, Massimiliano and Mironowicz, Piotr and Nawareg, Mohamed and Pawłowski, Marcin and Cabello, Adán and Bourennane, Mohamed}, month = feb, year = {2020}, pages = {123}, }`

- Géza Tóth, Tamás Vértesi, Paweł Horodecki, and Ryszard Horodecki. Activating Hidden Metrological Usefulness.
*Physical Review Letters*, 125(2):020402, jul 2020. doi:10.1103/PhysRevLett.125.020402

[BibTeX] [Download PDF]`@Article{toth_activating_2020, author = {Tóth, Géza and Vértesi, Tamás and Horodecki, Paweł and Horodecki, Ryszard}, journal = {Physical {R}eview {L}etters}, title = {Activating {Hidden} {Metrological} {Usefulness}}, year = {2020}, issn = {0031-9007, 1079-7114}, month = jul, number = {2}, pages = {020402}, volume = {125}, doi = {10.1103/PhysRevLett.125.020402}, groups = {Pawel_H}, language = {en}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.125.020402}, urldate = {2021-05-10}, }`

- Ravishankar Ramanathan, Monika Rosicka, Karol Horodecki, Stefano Pironio, Michał Horodecki, and Paweł Horodecki. Gadget structures in proofs of the Kochen-Specker theorem.
*Quantum*, 4:308, aug 2020. doi:10.22331/q-2020-08-14-308

[BibTeX] [Abstract] [Download PDF]

The Kochen-Specker theorem is a fundamental result in quantum foundations that has spawned massive interest since its inception. We show that within every Kochen-Specker graph, there exist interesting subgraphs which we term 01 -gadgets, that capture the essential contradiction necessary to prove the Kochen-Specker theorem, i.e,. every Kochen-Specker graph contains a 01 -gadget and from every 01 -gadget one can construct a proof of the Kochen-Specker theorem. Moreover, we show that the 01 -gadgets form a fundamental primitive that can be used to formulate state-independent and state-dependent statistical Kochen-Specker arguments as well as to give simple constructive proofs of an “extended” Kochen-Specker theorem first considered by Pitowsky in \textbackslashcite\Pitowsky\.

`@Article{ramanathan_gadget_2020, author = {Ramanathan, Ravishankar and Rosicka, Monika and Horodecki, Karol and Pironio, Stefano and Horodecki, Michał and Horodecki, Paweł}, journal = {Quantum}, title = {Gadget structures in proofs of the {Kochen}-{Specker} theorem}, year = {2020}, issn = {2521-327X}, month = aug, pages = {308}, volume = {4}, abstract = {The Kochen-Specker theorem is a fundamental result in quantum foundations that has spawned massive interest since its inception. We show that within every Kochen-Specker graph, there exist interesting subgraphs which we term 01 -gadgets, that capture the essential contradiction necessary to prove the Kochen-Specker theorem, i.e,. every Kochen-Specker graph contains a 01 -gadget and from every 01 -gadget one can construct a proof of the Kochen-Specker theorem. Moreover, we show that the 01 -gadgets form a fundamental primitive that can be used to formulate state-independent and state-dependent statistical Kochen-Specker arguments as well as to give simple constructive proofs of an ``extended'' Kochen-Specker theorem first considered by Pitowsky in {\textbackslash}cite\{Pitowsky\}.}, doi = {10.22331/q-2020-08-14-308}, groups = {Pawel_H, Michal_H}, language = {en}, url = {https://quantum-journal.org/papers/q-2020-08-14-308/}, urldate = {2021-05-10}, }`

- Michał Eckstein and Paweł Horodecki. The Experiment Paradox in Physics.
*Foundations of Science*, oct 2020. doi:10.1007/s10699-020-09711-y

[BibTeX] [Abstract] [Download PDF]

Abstract Modern physics is founded on two mainstays: mathematical modelling and empirical verification. These two assumptions are prerequisite for the objectivity of scientific discourse. Here we show, however, that they are contradictory, leading to the ‘experiment paradox’. We reveal that any experiment performed on a physical system is—by necessity—invasive and thus establishes inevitable limits to the accuracy of any mathematical model. We track its manifestations in both classical and quantum physics and show how it is overcome ‘in practice’ via the concept of environment. We argue that the unravelled paradox induces a new type of ‘ontic’ underdetermination, which has deep consequences for the methodological foundations of physics.

`@Article{eckstein_experiment_2020, author = {Eckstein, Michał and Horodecki, Paweł}, journal = {Foundations of {S}cience}, title = {The {Experiment} {Paradox} in {Physics}}, year = {2020}, issn = {1233-1821, 1572-8471}, month = oct, abstract = {Abstract Modern physics is founded on two mainstays: mathematical modelling and empirical verification. These two assumptions are prerequisite for the objectivity of scientific discourse. Here we show, however, that they are contradictory, leading to the ‘experiment paradox’. We reveal that any experiment performed on a physical system is—by necessity—invasive and thus establishes inevitable limits to the accuracy of any mathematical model. We track its manifestations in both classical and quantum physics and show how it is overcome ‘in practice’ via the concept of environment. We argue that the unravelled paradox induces a new type of ‘ontic’ underdetermination, which has deep consequences for the methodological foundations of physics.}, doi = {10.1007/s10699-020-09711-y}, groups = {Pawel_H}, language = {en}, url = {http://link.springer.com/10.1007/s10699-020-09711-y}, urldate = {2021-05-10}, }`

- Alley Hameedi, Breno Marques, Piotr Mironowicz, Debashis Saha, Marcin Pawłowski, and Mohamed Bourennane. Experimental test of nonclassicality with arbitrarily low detection efficiency.
*Physical Review A*, 102(3):032621, sep 2020. doi:10.1103/PhysRevA.102.032621

[BibTeX] [Download PDF]`@Article{hameedi_experimental_2020, author = {Hameedi, Alley and Marques, Breno and Mironowicz, Piotr and Saha, Debashis and Pawłowski, Marcin and Bourennane, Mohamed}, journal = {Physical {R}eview {A}}, title = {Experimental test of nonclassicality with arbitrarily low detection efficiency}, year = {2020}, issn = {2469-9926, 2469-9934}, month = sep, number = {3}, pages = {032621}, volume = {102}, doi = {10.1103/PhysRevA.102.032621}, language = {en}, url = {https://link.aps.org/doi/10.1103/PhysRevA.102.032621}, urldate = {2021-05-10}, }`

- Thao P. Le, Piotr Mironowicz, and Paweł Horodecki. Blurred quantum Darwinism across quantum reference frames.
*Physical Review A*, 102(6):062420, dec 2020. doi:10.1103/PhysRevA.102.062420

[BibTeX] [Download PDF]`@Article{le_blurred_2020, author = {Le, Thao P. and Mironowicz, Piotr and Horodecki, Paweł}, journal = {Physical {R}eview {A}}, title = {Blurred quantum {Darwinism} across quantum reference frames}, year = {2020}, issn = {2469-9926, 2469-9934}, month = dec, number = {6}, pages = {062420}, volume = {102}, doi = {10.1103/PhysRevA.102.062420}, groups = {Pawel_H}, language = {en}, url = {https://link.aps.org/doi/10.1103/PhysRevA.102.062420}, urldate = {2021-05-10}, }`

- Michał Eckstein, Paweł Horodecki, Ryszard Horodecki, and Tomasz Miller. Operational causality in spacetime.
*Physical Review A*, 101(4):042128, apr 2020. arXiv: 1902.05002 doi:10.1103/PhysRevA.101.042128

[BibTeX] [Abstract] [Download PDF]

The no-signalling principle preventing superluminal communication is a limiting paradigm for physical theories. Within the information-theoretic framework it is commonly understood in terms of admissible correlations in composite systems. Here we unveil its complementary incarnation — the ‘dynamical no-signalling principle’ —, which forbids superluminal signalling via measurements on simple physical objects (e.g. particles) evolving in time. We show that it imposes strong constraints on admissible models of dynamics. The posited principle is universal — it can be applied to any theory (classical, quantum or post-quantum) with well-defined rules of calculating detection statistics in spacetime. As an immediate application we show how one could exploit the Schr\textbackslash”odinger equation to establish a fully operational superluminal protocol in the Minkowski spacetime. This example illustrates how the principle can be used to identify the limits of applicability of a given model of quantum or post-quantum dynamics.

`@Article{eckstein_operational_2020, author = {Eckstein, Michał and Horodecki, Paweł and Horodecki, Ryszard and Miller, Tomasz}, journal = {Physical {R}eview {A}}, title = {Operational causality in spacetime}, year = {2020}, issn = {2469-9926, 2469-9934}, month = apr, note = {arXiv: 1902.05002}, number = {4}, pages = {042128}, volume = {101}, abstract = {The no-signalling principle preventing superluminal communication is a limiting paradigm for physical theories. Within the information-theoretic framework it is commonly understood in terms of admissible correlations in composite systems. Here we unveil its complementary incarnation --- the 'dynamical no-signalling principle' ---, which forbids superluminal signalling via measurements on simple physical objects (e.g. particles) evolving in time. We show that it imposes strong constraints on admissible models of dynamics. The posited principle is universal --- it can be applied to any theory (classical, quantum or post-quantum) with well-defined rules of calculating detection statistics in spacetime. As an immediate application we show how one could exploit the Schr{\textbackslash}"odinger equation to establish a fully operational superluminal protocol in the Minkowski spacetime. This example illustrates how the principle can be used to identify the limits of applicability of a given model of quantum or post-quantum dynamics.}, doi = {10.1103/PhysRevA.101.042128}, groups = {Pawel_H}, keywords = {Quantum Physics, General Relativity and Quantum Cosmology, Mathematical Physics, 81P16 (Primary), 81P15, 28E99, 60B05 (Secondary)}, url = {http://arxiv.org/abs/1902.05002}, urldate = {2021-05-11}, }`

- Michał Eckstein, Paweł Horodecki, Ryszard Horodecki, and Tomasz Miller. Operational causality in spacetime.
*Physical Review A*, 101(4):042128, apr 2020. arXiv: 1902.05002 doi:10.1103/PhysRevA.101.042128

[BibTeX] [Abstract] [Download PDF]

The no-signalling principle preventing superluminal communication is a limiting paradigm for physical theories. Within the information-theoretic framework it is commonly understood in terms of admissible correlations in composite systems. Here we unveil its complementary incarnation — the ‘dynamical no-signalling principle’ —, which forbids superluminal signalling via measurements on simple physical objects (e.g. particles) evolving in time. We show that it imposes strong constraints on admissible models of dynamics. The posited principle is universal — it can be applied to any theory (classical, quantum or post-quantum) with well-defined rules of calculating detection statistics in spacetime. As an immediate application we show how one could exploit the Schr\textbackslash”odinger equation to establish a fully operational superluminal protocol in the Minkowski spacetime. This example illustrates how the principle can be used to identify the limits of applicability of a given model of quantum or post-quantum dynamics.

`@Article{eckstein_operational_2020-1, author = {Eckstein, Michał and Horodecki, Paweł and Horodecki, Ryszard and Miller, Tomasz}, journal = {Physical {R}eview {A}}, title = {Operational causality in spacetime}, year = {2020}, issn = {2469-9926, 2469-9934}, month = apr, note = {arXiv: 1902.05002}, number = {4}, pages = {042128}, volume = {101}, abstract = {The no-signalling principle preventing superluminal communication is a limiting paradigm for physical theories. Within the information-theoretic framework it is commonly understood in terms of admissible correlations in composite systems. Here we unveil its complementary incarnation --- the 'dynamical no-signalling principle' ---, which forbids superluminal signalling via measurements on simple physical objects (e.g. particles) evolving in time. We show that it imposes strong constraints on admissible models of dynamics. The posited principle is universal --- it can be applied to any theory (classical, quantum or post-quantum) with well-defined rules of calculating detection statistics in spacetime. As an immediate application we show how one could exploit the Schr{\textbackslash}"odinger equation to establish a fully operational superluminal protocol in the Minkowski spacetime. This example illustrates how the principle can be used to identify the limits of applicability of a given model of quantum or post-quantum dynamics.}, doi = {10.1103/PhysRevA.101.042128}, groups = {Pawel_H}, keywords = {Quantum Physics, General Relativity and Quantum Cosmology, Mathematical Physics, 81P16 (Primary), 81P15, 28E99, 60B05 (Secondary)}, url = {http://arxiv.org/abs/1902.05002}, urldate = {2021-07-28}, }`

### 2019

- Piotr Mironowicz and Marcin Pawłowski. Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements.
*Physical Review A*, 100(3):030301, sep 2019. doi:10.1103/PhysRevA.100.030301

[BibTeX] [Download PDF]`@Article{mironowicz_experimentally_2019, author = {Mironowicz, Piotr and Pawłowski, Marcin}, journal = {Physical {R}eview {A}}, title = {Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements}, year = {2019}, issn = {2469-9926, 2469-9934}, month = sep, number = {3}, pages = {030301}, volume = {100}, doi = {10.1103/PhysRevA.100.030301}, groups = {Pawlowski}, language = {en}, url = {https://link.aps.org/doi/10.1103/PhysRevA.100.030301}, urldate = {2020-04-22} }`

- Giuseppe Baio, Dariusz Chruściński, Paweł Horodecki, Antonino Messina, and Gniewomir Sarbicki. Bounds on the entanglement of two-qutrit systems from fixed marginals.
*Physical Review A*, 99(6):062312, jun 2019. doi:10.1103/PhysRevA.99.062312

[BibTeX] [Download PDF]`@Article{baio_bounds_2019, author = {Baio, Giuseppe and Chruściński, Dariusz and Horodecki, Paweł and Messina, Antonino and Sarbicki, Gniewomir}, journal = {Physical {R}eview {A}}, title = {Bounds on the entanglement of two-qutrit systems from fixed marginals}, year = {2019}, issn = {2469-9926, 2469-9934}, month = jun, number = {6}, pages = {062312}, volume = {99}, doi = {10.1103/PhysRevA.99.062312}, groups = {Pawel_H}, language = {en}, url = {https://link.aps.org/doi/10.1103/PhysRevA.99.062312}, urldate = {2020-04-22}, }`

- Paweł Horodecki and Ravishankar Ramanathan. The relativistic causality versus no-signaling paradigm for multi-party correlations.
*Nature Communications*, 10(1):1701, dec 2019. doi:10.1038/s41467-019-09505-2

[BibTeX] [Download PDF]`@Article{horodecki_relativistic_2019, author = {Horodecki, Paweł and Ramanathan, Ravishankar}, journal = {Nature {C}ommunications}, title = {The relativistic causality versus no-signaling paradigm for multi-party correlations}, year = {2019}, issn = {2041-1723}, month = dec, number = {1}, pages = {1701}, volume = {10}, doi = {10.1038/s41467-019-09505-2}, groups = {Pawel_H}, language = {en}, url = {http://www.nature.com/articles/s41467-019-09505-2}, urldate = {2020-04-22}, }`

## arXiv preprints

### 2022

- Michał Banacki, Ravishankar Ramanathan, and Paweł Horodecki. Multipartite channel assemblages.
*arXiv:2205.05033 [quant-ph]*, may 2022. acknowledgement for ICTQT IRAP included

[BibTeX] [Abstract] [Download PDF]

Motivated by the recent studies on post-quantum steering, we generalize the notion of bipartite channel steering by introducing the concept of multipartite no-signaling channel assemblages. We first show that beyond the bipartite case, the no-signaling and quantum descriptions of channel assemblages do not coincide. Using the Choi-Jamiołkowski isomorphism, we present a complete characterization of these classes of assemblages and use this characterization to provide sufficient conditions for extremality of quantum channel assemblages within the set of all no-signaling channel assemblages. Finally, we introduce and discuss a relaxed version of channel steering where only certain subsystems obey the no-signaling constraints. In this latter asymmetric scenario we show the possibility of certifying a perfect key bit that is secure against a general no-signaling eavesdropper.

`@Article{arxiv_banacki_multipartite_2022, author = {Banacki, Michał and Ramanathan, Ravishankar and Horodecki, Paweł}, journal = {arXiv:2205.05033 [quant-ph]}, title = {Multipartite channel assemblages}, note = {acknowledgement for ICTQT IRAP included}, year = {2022}, month = may, note = {arXiv: 2205.05033}, abstract = {Motivated by the recent studies on post-quantum steering, we generalize the notion of bipartite channel steering by introducing the concept of multipartite no-signaling channel assemblages. We first show that beyond the bipartite case, the no-signaling and quantum descriptions of channel assemblages do not coincide. Using the Choi-Jamiołkowski isomorphism, we present a complete characterization of these classes of assemblages and use this characterization to provide sufficient conditions for extremality of quantum channel assemblages within the set of all no-signaling channel assemblages. Finally, we introduce and discuss a relaxed version of channel steering where only certain subsystems obey the no-signaling constraints. In this latter asymmetric scenario we show the possibility of certifying a perfect key bit that is secure against a general no-signaling eavesdropper.}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {https://arxiv.org/abs/2205.05033}, }`

- RR Rodriguez, B. Ahmadi, G. Suarez, P. Mazurek, S. Barzanjeh, and P. Horodecki. Optimal Quantum Control of Charging Quantum Batteries.
*arXiv preprint arXiv:2207.00094*, 2022. acknowledgement for ICTQT IRAP included

[BibTeX]`@article{rodriguez2022optimal, title={Optimal Quantum Control of Charging Quantum Batteries}, author={Rodriguez, RR and Ahmadi, B and Suarez, G and Mazurek, P and Barzanjeh, S and Horodecki, P}, journal={arXiv preprint arXiv:2207.00094}, note= {acknowledgement for ICTQT IRAP included}, year={2022} }`

- Borhan Ahmadi, Pawel Mazurek, Ricard Ravell Rodriguez, Shabir Barzanjeh, Robert Alicki, and Pawel Horodecki. Catalysis in Charging Quantum Batteries.
*arXiv preprint arXiv:2205.05018*, 2022. acknowledgement for ICTQT IRAP included

[BibTeX]`@article{ahmadi2022catalysis, title={Catalysis in Charging Quantum Batteries}, author={Ahmadi, Borhan and Mazurek, Pawel and Rodriguez, Ricard Ravell and Barzanjeh, Shabir and Alicki, Robert and Horodecki, Pawel}, journal={arXiv preprint arXiv:2205.05018}, note= {acknowledgement for ICTQT IRAP included}, year={2022} }`

- Karol Horodecki, Jingfang Zhou, Maciej Stankiewicz, Roberto Salazar, Paweł Horodecki, Robert Raussendorf, Ryszard Horodecki, Ravishankar Ramanathan, and Emily Tyhurst. The rank of contextuality. , 2022. doi:10.48550/ARXIV.2205.10307

[BibTeX] [Download PDF]`@article{https://doi.org/10.48550/arxiv.2205.10307, doi = {10.48550/ARXIV.2205.10307}, url = {https://arxiv.org/abs/2205.10307}, author = {Horodecki, Karol and Zhou, Jingfang and Stankiewicz, Maciej and Salazar, Roberto and Horodecki, Paweł and Raussendorf, Robert and Horodecki, Ryszard and Ramanathan, Ravishankar and Tyhurst, Emily}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {The rank of contextuality}, publisher = {arXiv}, year = {2022}, copyright = {arXiv.org perpetual, non-exclusive license} }`

- Róbert Trényi, Árpád Lukács, Paweł Horodecki, Ryszard Horodecki, Tamás Vértesi, and Géza Tóth. Multicopy metrology with many-particle quantum states.
*arXiv:2203.05538 [quant-ph]*, mar 2022. acknowledgement for ICTQT IRAP included

[BibTeX] [Download PDF]`@article{arxiv_Trenyi_Multicopy_2022, author = {Trényi, Róbert and Lukács, Árpád and Horodecki, Paweł and Horodecki, Ryszard and Vértesi, Tamás and Tóth, Géza}, journal = {arXiv:2203.05538 [quant-ph]}, title = {Multicopy metrology with many-particle quantum states}, note= {acknowledgement for ICTQT IRAP included}, year = {2022}, month = mar, note = {arXiv: 2203.05538}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {https://arxiv.org/abs/2203.05538}, }`

- Shuai Zhao, Ravishankar Ramanathan, Yuan Liu, and Paweł Horodecki. Tilted Hardy paradoxes for device-independent randomness extraction. , may 2022. acknowledgement for ICTQT IRAP included doi:10.48550/ARXIV.2205.02751

[BibTeX] [Download PDF]`@article{arxiv_Zhao_Tilted_2022, doi = {10.48550/ARXIV.2205.02751}, url = {https://arxiv.org/abs/2205.02751}, author = {Zhao, Shuai and Ramanathan, Ravishankar and Liu, Yuan and Horodecki, Paweł}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {Tilted Hardy paradoxes for device-independent randomness extraction}, note= {acknowledgement for ICTQT IRAP included}, publisher = {arXiv}, year = {2022}, copyright = {arXiv.org perpetual, non-exclusive license}, month = may, note = {arXiv: 2205.02751}, groups = {Pawel_H}, }`

- Karol Horodecki, Jingfang Zhou, Maciej Stankiewicz, Roberto Salazar, Paweł Horodecki, Robert Raussendorf, Ryszard Horodecki, Ravishankar Ramanathan, and Emily Tyhurst. The rank of contextuality. , may 2022. acknowledgement for ICTQT IRAP included doi:10.48550/ARXIV.2205.10307

[BibTeX] [Download PDF]`@article{arxiv_Horodecki_The_2022, doi = {10.48550/ARXIV.2205.10307}, url = {https://arxiv.org/abs/2205.10307}, author = {Horodecki, Karol and Zhou, Jingfang and Stankiewicz, Maciej and Salazar, Roberto and Horodecki, Paweł and Raussendorf, Robert and Horodecki, Ryszard and Ramanathan, Ravishankar and Tyhurst, Emily}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {The rank of contextuality}, note= {acknowledgement for ICTQT IRAP included}, publisher = {arXiv}, year = {2022}, copyright = {arXiv.org perpetual, non-exclusive license}, month = may, note = {arXiv: 2205.10307}, groups = {Pawel_H}, }`

- Yuan Liu, Ravishankar Ramanathan, Karol Horodecki, Monika Rosicka, and Paweł Horodecki. Optimal Measurement Structures for Contextuality Applications. , jun 2022. acknowledgement for ICTQT IRAP included doi:10.48550/ARXIV.2206.13139

[BibTeX] [Download PDF]`@article{arxiv_Liu_Optimal_2022, doi = {10.48550/ARXIV.2206.13139}, url = {https://arxiv.org/abs/2206.13139}, author = {Liu, Yuan and Ramanathan, Ravishankar and Horodecki, Karol and Rosicka, Monika and Horodecki, Paweł}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {Optimal Measurement Structures for Contextuality Applications}, note= {acknowledgement for ICTQT IRAP included}, publisher = {arXiv}, year = {2022}, copyright = {arXiv.org perpetual, non-exclusive license}, month = jun, note = {arXiv: 2206.13139}, groups = {Pawel_H}, }`

- Nitica Sakharwade, Michał Studzi’nski, Michał Eckstein, and Paweł Horodecki. Two instances of random access code in the quantum regime.
*arXiv preprint arXiv:2208.14422*, 2022. acknowledgement for ICTQT IRAP included

[BibTeX]`@article{sakharwade2022two, title={Two instances of random access code in the quantum regime}, author={Sakharwade, Nitica and Studzi{\'n}ski, Micha{\l} and Eckstein, Micha{\l} and Horodecki, Pawe{\l}}, journal={arXiv preprint arXiv:2208.14422}, note= {acknowledgement for ICTQT IRAP included}, year={2022} }`

- Ram Krishna Patra, Sahil Gopalkrishna Naik, Edwin Peter Lobo, Samrat Sen, Tamal Guha, Some Sankar Bhattacharya, Mir Alimuddin, and Manik Banik. *Classical superdense coding and communication advantage of a single quantum. , feb 2022. arXiv: 2202.06796 doi:10.48550/ARXIV.2202.06796

[BibTeX] [Download PDF]`@article{arxiv_Patra_Classical_2022, doi = {10.48550/ARXIV.2202.06796}, url = {https://arxiv.org/abs/2202.06796}, author = {Patra, Ram Krishna and Naik, Sahil Gopalkrishna and Lobo, Edwin Peter and Sen, Samrat and Guha, Tamal and Bhattacharya, Some Sankar and Alimuddin, Mir and Banik, Manik}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {*Classical superdense coding and communication advantage of a single quantum}, publisher = {arXiv}, year = {2022}, copyright = {Creative Commons Attribution 4.0 International}, month = feb, note = {arXiv: 2202.06796}, groups = {Pawel_H}, }`

- Piotr Mironowicz. Quantum security and theory of decoherence.
*arXiv preprint arXiv:2205.12927*, 2022.

[BibTeX]`@article{mironowicz2022quantum, title={Quantum security and theory of decoherence}, author={Mironowicz, Piotr}, journal={arXiv preprint arXiv:2205.12927}, year={2022} }`

- Piotr Mironowicz. Entangled Rendezvous: A Possible Application of Bell Non-Locality For Mobile Agents on Networks.
*arXiv preprint arXiv:2207.14404*, 2022.

[BibTeX]`@article{mironowicz2022entangled, title={Entangled Rendezvous: A Possible Application of Bell Non-Locality For Mobile Agents on Networks}, author={Mironowicz, Piotr}, journal={arXiv preprint arXiv:2207.14404}, year={2022} }`

### 2021

- John H. Selby, Ana Belén Sainz, and Paweł Horodecki. Revisiting dynamics of quantum causal structures — when can causal order evolve?.
*arXiv:2008.12757 [quant-ph]*, mar 2021. arXiv: 2008.12757

[BibTeX] [Abstract] [Download PDF]

Recently, there has been substantial interest in studying the dynamics of quantum theory beyond that of states, in particular, the dynamics of channels, measurements, and higher-order transformations. Ref. [Phys. Rev. X 8(1), 011047 (2018)] pursues this using the process matrix formalism, together with a definition of the possible dynamics of such process matrices, and focusing especially on the question of evolution of causal structures. One of its major conclusions is a strong theorem saying that, within the formalism, under continuous and reversible transformations, the causal order between operations must be preserved. Here we find a surprising result: if one is to take into account a full picture of the physical evolution of operations within the standard quantum-mechanical formalism, then one can actually draw the opposite conclusion. That is, we show that under certain continuous and reversible dynamics the causal order between operations is not necessarily preserved. We moreover identify and analyse the root of this apparent contradiction, specifically, that the commonly accepted and widely applied framework of higher-order processes, whilst mathematically sound, is not always appropriate for drawing conclusions on the fundamentals of physical dynamics. Finally we show how to reconcile the elements of the whole picture following the intuition based on entanglement processing by local operations and classical communication.

`@Article{selby_revisiting_2021, author = {Selby, John H. and Sainz, Ana Belén and Horodecki, Paweł}, journal = {arXiv:2008.12757 [quant-ph]}, title = {Revisiting dynamics of quantum causal structures -- when can causal order evolve?}, year = {2021}, month = mar, note = {arXiv: 2008.12757}, abstract = {Recently, there has been substantial interest in studying the dynamics of quantum theory beyond that of states, in particular, the dynamics of channels, measurements, and higher-order transformations. Ref. [Phys. Rev. X 8(1), 011047 (2018)] pursues this using the process matrix formalism, together with a definition of the possible dynamics of such process matrices, and focusing especially on the question of evolution of causal structures. One of its major conclusions is a strong theorem saying that, within the formalism, under continuous and reversible transformations, the causal order between operations must be preserved. Here we find a surprising result: if one is to take into account a full picture of the physical evolution of operations within the standard quantum-mechanical formalism, then one can actually draw the opposite conclusion. That is, we show that under certain continuous and reversible dynamics the causal order between operations is not necessarily preserved. We moreover identify and analyse the root of this apparent contradiction, specifically, that the commonly accepted and widely applied framework of higher-order processes, whilst mathematically sound, is not always appropriate for drawing conclusions on the fundamentals of physical dynamics. Finally we show how to reconcile the elements of the whole picture following the intuition based on entanglement processing by local operations and classical communication.}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/2008.12757}, urldate = {2021-07-28}, }`

- B. Ahmadi, S. Salimi, and A. S. Khorashad. Refined Definitions of Heat and Work in Quantum Thermodynamics.
*arXiv:1912.01983 [quant-ph]*, jul 2021. arXiv: 1912.01983

[BibTeX] [Abstract] [Download PDF]

In this paper, unambiguous redefinitions of heat and work are presented for quantum thermodynamic systems. We will use genuine reasoning based on which Clausius originally defined work and heat in establishing thermodynamics. The change in the energy which is accompanied by a change in the entropy is identified as heat, while any change in the energy which does not lead to a change in the entropy is known as work. It will be seen that quantum coherence does not allow all the energy exchanged between two quantum systems to be only of the heat form. Several examples will also be discussed. Finally, it will be shown that these refined definitions will strongly affect the entropy production of quantum thermodynamic processes giving new insight into the irreversibility of quantum processes.

`@Article{ahmadi_refined_2021, author = {Ahmadi, B. and Salimi, S. and Khorashad, A. S.}, journal = {arXiv:1912.01983 [quant-ph]}, title = {Refined {Definitions} of {Heat} and {Work} in {Quantum} {Thermodynamics}}, year = {2021}, month = jul, note = {arXiv: 1912.01983}, abstract = {In this paper, unambiguous redefinitions of heat and work are presented for quantum thermodynamic systems. We will use genuine reasoning based on which Clausius originally defined work and heat in establishing thermodynamics. The change in the energy which is accompanied by a change in the entropy is identified as heat, while any change in the energy which does not lead to a change in the entropy is known as work. It will be seen that quantum coherence does not allow all the energy exchanged between two quantum systems to be only of the heat form. Several examples will also be discussed. Finally, it will be shown that these refined definitions will strongly affect the entropy production of quantum thermodynamic processes giving new insight into the irreversibility of quantum processes.}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/1912.01983}, urldate = {2021-07-28}, }`

- Ray Ganardi, Marek Miller, Tomasz Paterek, and Marek Żukowski. Hierarchy of correlation quantifiers comparable to negativity.
*arXiv e-prints*, pages arXiv:2111.11887, nov 2021.

[BibTeX] [Abstract] [Download PDF]

Quantum systems generally exhibit different kinds of correlations. In order to compare them on equal footing, one uses the so-called distance-based approach where different types of correlations are captured by the distance to different set of states. However, these quantifiers are usually hard to compute as their definition involves optimization aiming to find the closest states within the set. On the other hand, negativity is one of the few computable entanglement monotones, but its comparison with other correlations required further justification. Here we place negativity as part of a family of correlation measures that has a distance-based construction. We introduce a suitable distance, discuss the emerging measures and their applications, and compare them to relative entropy-based correlation quantifiers. This work is a step towards correlation measures that are simultaneously comparable and computable.

`@Article{Ganardi2021, author = {Ganardi, Ray and Miller, Marek and Paterek, Tomasz and {\.Z}ukowski, Marek}, journal = {arXiv e-prints}, title = {Hierarchy of correlation quantifiers comparable to negativity}, year = {2021}, month = nov, pages = {arXiv:2111.11887}, abstract = {Quantum systems generally exhibit different kinds of correlations. In order to compare them on equal footing, one uses the so-called distance-based approach where different types of correlations are captured by the distance to different set of states. However, these quantifiers are usually hard to compute as their definition involves optimization aiming to find the closest states within the set. On the other hand, negativity is one of the few computable entanglement monotones, but its comparison with other correlations required further justification. Here we place negativity as part of a family of correlation measures that has a distance-based construction. We introduce a suitable distance, discuss the emerging measures and their applications, and compare them to relative entropy-based correlation quantifiers. This work is a step towards correlation measures that are simultaneously comparable and computable.}, archiveprefix = {arXiv}, eid = {arXiv:2111.11887}, eprint = {2111.11887}, keywords = {Quantum Physics}, primaryclass = {quant-ph}, url = {https://ui.adsabs.harvard.edu/abs/2021arXiv211111887G}, }`

- Ravishankar Ramanathan, Michał Banacki, and Paweł Horodecki. No-signaling-proof randomness extraction from public weak sources.
*arXiv:2108.08819 [quant-ph]*, aug 2021. acknowledgement for ICTQT IRAP included

[BibTeX] [Abstract] [Download PDF]

The extraction of randomness from weakly random seeds is a topic of central importance in cryptography. Weak sources of randomness can be considered to be either private or public, where public sources such as the NIST randomness beacon broadcast the random bits once they are generated. The problem of device-independent randomness extraction from weak public sources against no-signalling adversaries has remained open. In this paper, we show protocols for device-independent and one-sided device-independent amplification of randomness from weak public Santha Vazirani (SV) sources that use a finite number of devices and are secure against no-signaling adversaries. Specifically, under the assumption that the device behavior is as prescribed by quantum mechanics the protocols allow for amplification of public $\epsilon$-SV sources for arbitrary initial $\epsilon\in łeft[0,0.5\right)$. On the other hand, when only the assumption of no-signaling between the components of the device is made, the protocols allow for amplification of a limited set of weak public SV sources.

`@Article{arxiv_ramanathan_no-signaling-proof_2021, author = {Ramanathan, Ravishankar and Banacki, Michał and Horodecki, Paweł}, journal = {arXiv:2108.08819 [quant-ph]}, title = {No-signaling-proof randomness extraction from public weak sources}, note = {acknowledgement for ICTQT IRAP included}, year = {2021}, month = aug, note = {arXiv: 2108.08819}, abstract = {The extraction of randomness from weakly random seeds is a topic of central importance in cryptography. Weak sources of randomness can be considered to be either private or public, where public sources such as the NIST randomness beacon broadcast the random bits once they are generated. The problem of device-independent randomness extraction from weak public sources against no-signalling adversaries has remained open. In this paper, we show protocols for device-independent and one-sided device-independent amplification of randomness from weak public Santha Vazirani (SV) sources that use a finite number of devices and are secure against no-signaling adversaries. Specifically, under the assumption that the device behavior is as prescribed by quantum mechanics the protocols allow for amplification of public $\epsilon$-SV sources for arbitrary initial $\epsilon\in \left[0,0.5\right)$. On the other hand, when only the assumption of no-signaling between the components of the device is made, the protocols allow for amplification of a limited set of weak public SV sources.}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {https://arxiv.org/abs/2108.08819}, }`

### 2020

- Ravishankar Ramanathan, Michał Horodecki, Hammad Anwer, Stefano Pironio, Karol Horodecki, Marcus Grünfeld, Sadiq Muhammad, Mohamed Bourennane, and Paweł Horodecki. Practical No-Signalling proof Randomness Amplification using Hardy paradoxes and its experimental implementation.
*arXiv:1810.11648 [quant-ph]*, sep 2020. arXiv: 1810.11648

[BibTeX] [Abstract] [Download PDF]

Device-Independent (DI) security is the best form of quantum cryptography, providing information-theoretic security based on the very laws of nature. In its highest form, security is guaranteed against adversaries limited only by the no-superluminal signalling rule of relativity. The task of randomness amplification, to generate secure fully uniform bits starting from weakly random seeds, is of both cryptographic and foundational interest, being important for the generation of cryptographically secure random numbers as well as bringing deep connections to the existence of free-will. DI no-signalling proof protocols for this fundamental task have thus far relied on esoteric proofs of non-locality termed pseudo-telepathy games, complicated multi-party setups or high-dimensional quantum systems, and have remained out of reach of experimental implementation. In this paper, we construct the first practically relevant no-signalling proof DI protocols for randomness amplification based on the simplest proofs of Bell non-locality and illustrate them with an experimental implementation in a quantum optical setup using polarised photons. Technically, we relate the problem to the vast field of Hardy paradoxes, without which it would be impossible to achieve amplification of arbitrarily weak sources in the simplest Bell non-locality scenario consisting of two parties choosing between two binary inputs. Furthermore, we identify a deep connection between proofs of the celebrated Kochen-Specker theorem and Hardy paradoxes that enables us to construct Hardy paradoxes with the non-zero probability taking any value in \$(0,1]\$. Our methods enable us, under the fair-sampling assumption of the experiment, to realize up to \$25\$ bits of randomness in \$20\$ hours of experimental data collection from an initial private source of randomness \$0.1\$ away from uniform.

`@Article{ramanathan_practical_2020, author = {Ramanathan, Ravishankar and Horodecki, Michał and Anwer, Hammad and Pironio, Stefano and Horodecki, Karol and Grünfeld, Marcus and Muhammad, Sadiq and Bourennane, Mohamed and Horodecki, Paweł}, journal = {arXiv:1810.11648 [quant-ph]}, title = {Practical {No}-{Signalling} proof {Randomness} {Amplification} using {Hardy} paradoxes and its experimental implementation}, year = {2020}, month = sep, note = {arXiv: 1810.11648}, abstract = {Device-Independent (DI) security is the best form of quantum cryptography, providing information-theoretic security based on the very laws of nature. In its highest form, security is guaranteed against adversaries limited only by the no-superluminal signalling rule of relativity. The task of randomness amplification, to generate secure fully uniform bits starting from weakly random seeds, is of both cryptographic and foundational interest, being important for the generation of cryptographically secure random numbers as well as bringing deep connections to the existence of free-will. DI no-signalling proof protocols for this fundamental task have thus far relied on esoteric proofs of non-locality termed pseudo-telepathy games, complicated multi-party setups or high-dimensional quantum systems, and have remained out of reach of experimental implementation. In this paper, we construct the first practically relevant no-signalling proof DI protocols for randomness amplification based on the simplest proofs of Bell non-locality and illustrate them with an experimental implementation in a quantum optical setup using polarised photons. Technically, we relate the problem to the vast field of Hardy paradoxes, without which it would be impossible to achieve amplification of arbitrarily weak sources in the simplest Bell non-locality scenario consisting of two parties choosing between two binary inputs. Furthermore, we identify a deep connection between proofs of the celebrated Kochen-Specker theorem and Hardy paradoxes that enables us to construct Hardy paradoxes with the non-zero probability taking any value in \$(0,1]\$. Our methods enable us, under the fair-sampling assumption of the experiment, to realize up to \$25\$ bits of randomness in \$20\$ hours of experimental data collection from an initial private source of randomness \$0.1\$ away from uniform.}, groups = {Michal_H, Pawel_H}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/1810.11648}, urldate = {2021-05-11}, }`

- Michał Banacki, Marcin Marciniak, Karol Horodecki, and Paweł Horodecki. Information backflow may not indicate quantum memory.
*arXiv:2008.12638 [quant-ph]*, aug 2020. arXiv: 2008.12638

[BibTeX] [Abstract] [Download PDF]

We analyze recent approaches to quantum Markovianity and how they relate to the proper definition of quantum memory. We point out that the well-known criterion of information backflow may not correctly report character of the memory falsely signaling its quantumness. Therefore, as a complement to the well-known criteria, we propose several concepts of elementary dynamical maps. Maps of this type do not increase distinguishability of states which are indistinguishable by von Neumann measurements in a given basis. Those notions and convexity allows us to define general classes of processes without quantum memory in a weak and strong sense. Finally, we provide a practical characterization of the most intuitive class in terms of the new concept of witness of quantum information backflow.

`@Article{banacki_information_2020, author = {Banacki, Michał and Marciniak, Marcin and Horodecki, Karol and Horodecki, Paweł}, journal = {arXiv:2008.12638 [quant-ph]}, title = {Information backflow may not indicate quantum memory}, year = {2020}, month = aug, note = {arXiv: 2008.12638}, abstract = {We analyze recent approaches to quantum Markovianity and how they relate to the proper definition of quantum memory. We point out that the well-known criterion of information backflow may not correctly report character of the memory falsely signaling its quantumness. Therefore, as a complement to the well-known criteria, we propose several concepts of elementary dynamical maps. Maps of this type do not increase distinguishability of states which are indistinguishable by von Neumann measurements in a given basis. Those notions and convexity allows us to define general classes of processes without quantum memory in a weak and strong sense. Finally, we provide a practical characterization of the most intuitive class in terms of the new concept of witness of quantum information backflow.}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/2008.12638}, urldate = {2021-07-28}, }`

- Ravishankar Ramanathan, Michał Banacki, Ricard Ravell Rodríguez, and Paweł Horodecki. Single trusted qubit is necessary and sufficient for quantum realisation of extremal no-signaling correlations.
*arXiv:2004.14782 [quant-ph]*, apr 2020. arXiv: 2004.14782

[BibTeX] [Abstract] [Download PDF]

Quantum statistics can be considered from the perspective of postquantum no-signaling theories in which either none or only a certain number of quantum systems are trusted. In these scenarios, the role of states is played by the so-called no-signaling boxes or no-signaling assemblages respectively. It has been shown so far that in the usual Bell non-locality scenario with a single measurement run, quantum statistics can never reproduce an extremal non-local point within the set of no-signaling boxes. We provide here a general no-go rule showing that the latter stays true even if arbitrary sequential measurements are allowed. On the other hand, we prove a positive result showing that already a single trusted qubit is enough for quantum theory to produce a self-testable extremal point within the corresponding set of no-signaling assemblages. This result opens up the possibility for security proofs of cryptographic protocols against general no-signaling adversaries.

`@Article{ramanathan_single_2020, author = {Ramanathan, Ravishankar and Banacki, Michał and Rodríguez, Ricard Ravell and Horodecki, Paweł}, journal = {arXiv:2004.14782 [quant-ph]}, title = {Single trusted qubit is necessary and sufficient for quantum realisation of extremal no-signaling correlations}, year = {2020}, month = apr, note = {arXiv: 2004.14782}, abstract = {Quantum statistics can be considered from the perspective of postquantum no-signaling theories in which either none or only a certain number of quantum systems are trusted. In these scenarios, the role of states is played by the so-called no-signaling boxes or no-signaling assemblages respectively. It has been shown so far that in the usual Bell non-locality scenario with a single measurement run, quantum statistics can never reproduce an extremal non-local point within the set of no-signaling boxes. We provide here a general no-go rule showing that the latter stays true even if arbitrary sequential measurements are allowed. On the other hand, we prove a positive result showing that already a single trusted qubit is enough for quantum theory to produce a self-testable extremal point within the corresponding set of no-signaling assemblages. This result opens up the possibility for security proofs of cryptographic protocols against general no-signaling adversaries.}, groups = {Pawel_H}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/2004.14782}, urldate = {2021-07-28}, }`

- B. Ahmadi, S. Salimi, and A. S. Khorashad. No Entropy Production in Quantum Thermodynamics.
*arXiv:2002.10747 [quant-ph]*, feb 2020. arXiv: 2002.10747

[BibTeX] [Abstract] [Download PDF]

In this work we will show that there exists a fundamental difference between microscopic quantum thermodynamics and macroscopic classical thermodynamics. It will be proved that the entropy production in quantum thermodynamics always vanishes for both closed and open quantum thermodynamic systems. This novel and very surprising result is derived based on the genuine reasoning Clausius used to establish the science of thermodynamics in the first place. This result will interestingly lead to define the generalized temperature for any non-equilibrium quantum system.

`@article{ahmadi_no_2020, title = {No {Entropy} {Production} in {Quantum} {Thermodynamics}}, url = {http://arxiv.org/abs/2002.10747}, abstract = {In this work we will show that there exists a fundamental difference between microscopic quantum thermodynamics and macroscopic classical thermodynamics. It will be proved that the entropy production in quantum thermodynamics always vanishes for both closed and open quantum thermodynamic systems. This novel and very surprising result is derived based on the genuine reasoning Clausius used to establish the science of thermodynamics in the first place. This result will interestingly lead to define the generalized temperature for any non-equilibrium quantum system.}, urldate = {2021-07-28}, journal = {arXiv:2002.10747 [quant-ph]}, author = {Ahmadi, B. and Salimi, S. and Khorashad, A. S.}, month = feb, year = {2020}, note = {arXiv: 2002.10747}, keywords = {Quantum Physics}, }`

### 2019

- Michał Eckstein and Paweł Horodecki. The experiment paradox in physics.
*arXiv:1904.04117 [gr-qc, physics:hep-th, physics:physics, physics:quant-ph]*, apr 2019. arXiv: 1904.04117

[BibTeX] [Abstract] [Download PDF]

Modern physics is founded on two mainstays: mathematical modelling and empirical verification. These two assumptions are prerequisite for the objectivity of scientific discourse. Here we show, however, that they are contradictory, leading to the `experiment paradox’. We reveal that any experiment performed on a physical system is – by necessity – invasive and thus establishes inevitable limits to the accuracy of any mathematical model. We track its manifestations in both classical and quantum physics and show how it is overcome `in practice’ via the concept of environment. We argue that the scientific pragmatism ordains two methodological principles of compressibility and stability.

`@Article{eckstein_experiment_2019, author = {Eckstein, Michał and Horodecki, Paweł}, journal = {arXiv:1904.04117 [gr-qc, physics:hep-th, physics:physics, physics:quant-ph]}, title = {The experiment paradox in physics}, year = {2019}, month = apr, note = {arXiv: 1904.04117}, abstract = {Modern physics is founded on two mainstays: mathematical modelling and empirical verification. These two assumptions are prerequisite for the objectivity of scientific discourse. Here we show, however, that they are contradictory, leading to the `experiment paradox'. We reveal that any experiment performed on a physical system is - by necessity - invasive and thus establishes inevitable limits to the accuracy of any mathematical model. We track its manifestations in both classical and quantum physics and show how it is overcome `in practice' via the concept of environment. We argue that the scientific pragmatism ordains two methodological principles of compressibility and stability.}, groups = {Pawel_H}, keywords = {Physics - History and Philosophy of Physics, General Relativity and Quantum Cosmology, High Energy Physics - Theory, Physics - Classical Physics, Quantum Physics}, url = {http://arxiv.org/abs/1904.04117}, urldate = {2021-07-28}, }`

- Sumit Rout, Ananda G. Maity, Amit Mukherjee, Saronath Halder, and Manik Banik. Multiparty orthogonal product states with minimal genuine nonlocality.
*arXiv:1910.14308 [quant-ph]*, oct 2019.

[BibTeX] [Abstract] [Download PDF]

Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. Concept of genuinely nonlocal set of product states emerges as a natural multipartite generalization of this phenomenon. Existence of such sets eventually motivates the problem concerning their entanglement-assisted discrimination. Here, we construct examples of genuinely nonlocal product states for arbitrary number of parties. Strength of genuine nonlocality of these sets can be considered minimal as their perfect discrimination is possible with entangled resources residing in Hilbert spaces having the smallest possible dimensions. Our constructions lead to fully separable measurements that are impossible to implement even if all but one party come together. Furthermore, they also provide the opportunity to compare different multipartite states that otherwise are incomparable under single copy local manipulation.

`@Article{Rout2019, author = {Sumit Rout and Ananda G. Maity and Amit Mukherjee and Saronath Halder and Manik Banik}, journal = {arXiv:1910.14308 [quant-ph]}, title = {Multiparty orthogonal product states with minimal genuine nonlocality}, year = {2019}, month = oct, abstract = {Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. Concept of genuinely nonlocal set of product states emerges as a natural multipartite generalization of this phenomenon. Existence of such sets eventually motivates the problem concerning their entanglement-assisted discrimination. Here, we construct examples of genuinely nonlocal product states for arbitrary number of parties. Strength of genuine nonlocality of these sets can be considered minimal as their perfect discrimination is possible with entangled resources residing in Hilbert spaces having the smallest possible dimensions. Our constructions lead to fully separable measurements that are impossible to implement even if all but one party come together. Furthermore, they also provide the opportunity to compare different multipartite states that otherwise are incomparable under single copy local manipulation.}, archiveprefix = {arXiv}, eprint = {1910.14308}, keywords = {quant-ph}, primaryclass = {quant-ph}, url = {https://arxiv.org/pdf/1910.14308}, }`

### 2018

- Marek Winczewski, Tamoghna Das, John H. Selby, Karol Horodecki, Paweł Horodecki, Łukasz Pankowski, Marco Piani, and Ravishankar Ramanathan. Complete extension: the non-signaling analog of quantum purification. , 2018. doi:10.48550/ARXIV.1810.02222

[BibTeX] [Download PDF]`@article{arXiv_complete_extension, doi = {10.48550/ARXIV.1810.02222}, url = {https://arxiv.org/abs/1810.02222}, author = {Winczewski, Marek and Das, Tamoghna and Selby, John H. and Horodecki, Karol and Horodecki, Paweł and Pankowski, Łukasz and Piani, Marco and Ramanathan, Ravishankar}, keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences}, title = {Complete extension: the non-signaling analog of quantum purification}, publisher = {arXiv}, year = {2018}, copyright = {arXiv.org perpetual, non-exclusive license} }`

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__Keywords:__ quantum entanglement, quantum contextuality, quantum computational speedup, quantum capacity, quantum channels, quantum reduction of communication complexity, violations of local realism, Bell’s theorem, resource theory of thermodynamics, resource theories, quantum networks, private bits, quantum privacy, quantum randomness, randomness amplification, device-independent randomness amplification, randomness extraction.