##### Leader of the research group: Marcin Pawłowski

Post-docs: Akshata Shenoy, Karthik Hosapete Seshadri, Pedro Ruas-Dieguez, Giovanni Scala

PhD student: Anubhav Chaturvedi, Giuseppe Viola, Chithra Raj, Tushita Prasad

The broad aim of the Quantum Cybersecurity and Communication Group is to develop quantum solutions for problems in communication and information security.

## Activity

Specific goals include the development of:

– Quantum key distribution protocols with low hardware requirements.

– Quantum true random number generators.

– Existing and new quantum cryptographic primitives.

– Methods for secure communication and computation.

– Formal security proofs of quantum cryptographic protocols.

– Tools for cryptoanalysis.

– Commercialisation and industrial outreach.

## Publications

### 2021

- 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}, }`

- Nikolai Miklin and Marcin Pawłowski. Information Causality without concatenation.
*Physical Review Letters*, 126(22):220403, jun 2021. arXiv: 2101.12710 doi:10.1103/PhysRevLett.126.220403

[BibTeX] [Abstract] [Download PDF]

Information Causality is a physical principle which states that the amount of randomly accessible data over a classical communication channel cannot exceed its capacity, even if the sender and the receiver have access to a source of nonlocal correlations. This principle can be used to bound the nonlocality of quantum mechanics without resorting to its full formalism, with a notable example of reproducing the Tsirelson’s bound of the Clauser-Horne-Shimony-Holt inequality. Despite being promising, the latter result found little generalization to other Bell inequalities because of the limitations imposed by the process of concatenation, in which several nonsignaling resources are put together to produce tighter bounds. In this work, we show that concatenation can be successfully replaced by limits on the communication channel capacity. It allows us to re-derive and, in some cases, significantly improve all the previously known results in a simpler manner and apply the Information Causality principle to previously unapproachable Bell scenarios.

`@Article{miklin_information_2021, author = {Miklin, Nikolai and Pawłowski, Marcin}, journal = {Physical {R}eview {L}etters}, title = {Information {Causality} without concatenation}, year = {2021}, issn = {0031-9007, 1079-7114}, month = jun, note = {arXiv: 2101.12710}, number = {22}, pages = {220403}, volume = {126}, abstract = {Information Causality is a physical principle which states that the amount of randomly accessible data over a classical communication channel cannot exceed its capacity, even if the sender and the receiver have access to a source of nonlocal correlations. This principle can be used to bound the nonlocality of quantum mechanics without resorting to its full formalism, with a notable example of reproducing the Tsirelson's bound of the Clauser-Horne-Shimony-Holt inequality. Despite being promising, the latter result found little generalization to other Bell inequalities because of the limitations imposed by the process of concatenation, in which several nonsignaling resources are put together to produce tighter bounds. In this work, we show that concatenation can be successfully replaced by limits on the communication channel capacity. It allows us to re-derive and, in some cases, significantly improve all the previously known results in a simpler manner and apply the Information Causality principle to previously unapproachable Bell scenarios.}, doi = {10.1103/PhysRevLett.126.220403}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/2101.12710}, urldate = {2021-07-28}, }`

- Wooyeong Song, Youngrong Lim, Hyukjoon Kwon, Gerardo Adesso, Marcin Wieśniak, Marcin Pawłowski, Jaewan Kim, and Jeongho Bang. Quantum secure learning with classical samples.
*Physical Review A*, 103(4):42409, apr 2021. arXiv: 1912.10594 doi:10.1103/PhysRevA.103.042409

[BibTeX] [Abstract] [Download PDF]

Studies addressing the question “Can a learner complete the learning securely?” have recently been spurred from the standpoints of fundamental theory and potential applications. In the relevant context of this question, we present a classical-quantum hybrid sampling protocol and define a security condition that allows only legitimate learners to prepare a finite set of samples that guarantees the success of the learning; the security condition excludes intruders. We do this by combining our security concept with the bound of the so-called probably approximately correct (PAC) learning. We show that while the lower bound on the learning samples guarantees PAC learning, an upper bound can be derived to rule out adversarial learners. Such a secure learning condition is appealing, because it is defined only by the size of samples required for the successful learning and is independent of the algorithm employed. Notably, the security stems from the fundamental quantum no-broadcasting principle. No such condition can thus occur in any classical regime, where learning samples can be copied. Owing to the hybrid architecture, our scheme also offers a practical advantage for implementation in noisy intermediate-scale quantum devices.

`@Article{song_quantum_2021, author = {Song, Wooyeong and Lim, Youngrong and Kwon, Hyukjoon and Adesso, Gerardo and Wieśniak, Marcin and Pawłowski, Marcin and Kim, Jaewan and Bang, Jeongho}, journal = {Physical {R}eview {A}}, title = {Quantum secure learning with classical samples}, year = {2021}, issn = {2469-9926, 2469-9934}, month = apr, note = {arXiv: 1912.10594}, number = {4}, pages = {042409}, volume = {103}, abstract = {Studies addressing the question "Can a learner complete the learning securely?" have recently been spurred from the standpoints of fundamental theory and potential applications. In the relevant context of this question, we present a classical-quantum hybrid sampling protocol and define a security condition that allows only legitimate learners to prepare a finite set of samples that guarantees the success of the learning; the security condition excludes intruders. We do this by combining our security concept with the bound of the so-called probably approximately correct (PAC) learning. We show that while the lower bound on the learning samples guarantees PAC learning, an upper bound can be derived to rule out adversarial learners. Such a secure learning condition is appealing, because it is defined only by the size of samples required for the successful learning and is independent of the algorithm employed. Notably, the security stems from the fundamental quantum no-broadcasting principle. No such condition can thus occur in any classical regime, where learning samples can be copied. Owing to the hybrid architecture, our scheme also offers a practical advantage for implementation in noisy intermediate-scale quantum devices.}, doi = {10.1103/PhysRevA.103.042409}, keywords = {Quantum Physics}, url = {http://arxiv.org/abs/1912.10594}, urldate = {2021-07-28}, }`

- Maciej Stankiewicz, Karol Horodecki, Omer Sakarya, and Danuta Makowiec. Private Weakly-Random Sequences from Human Heart Rate for Quantum Amplification.
*Entropy*, 23(9):1182, sep 2021. doi:10.3390/e23091182

[BibTeX] [Abstract] [Download PDF]

We investigate whether the heart rate can be treated as a semi-random source with the aim of amplification by quantum devices. We use a semi-random source model called $\epsilon$-Santha-Vazirani source, which can be amplified via quantum protocols to obtain fully private random sequence. We analyze time intervals between consecutive heartbeats obtained from Holter electrocardiogram (ECG) recordings of people of different sex and age. We propose several transformations of the original time series into binary sequences. We have performed different statistical randomness tests and estimated quality parameters. We find that the heart can be treated as good enough, and private by its nature, source of randomness, that every human possesses. As such, in principle it can be used as input to quantum device-independent randomness amplification protocols. The properly interpreted $\epsilon$ parameter can potentially serve as a new characteristic of the human’s heart from the perspective of medicine.

`@Article{Stankiewicz2021, author = {Stankiewicz, Maciej and Horodecki, Karol and Sakarya, Omer and Makowiec, Danuta}, journal = {Entropy}, title = {Private {W}eakly-{R}andom {S}equences from {H}uman {H}eart {R}ate for {Q}uantum {A}mplification}, year = {2021}, month = sep, number = {9}, pages = {1182}, volume = {23}, abstract = {We investigate whether the heart rate can be treated as a semi-random source with the aim of amplification by quantum devices. We use a semi-random source model called $\epsilon$-Santha-Vazirani source, which can be amplified via quantum protocols to obtain fully private random sequence. We analyze time intervals between consecutive heartbeats obtained from Holter electrocardiogram (ECG) recordings of people of different sex and age. We propose several transformations of the original time series into binary sequences. We have performed different statistical randomness tests and estimated quality parameters. We find that the heart can be treated as good enough, and private by its nature, source of randomness, that every human possesses. As such, in principle it can be used as input to quantum device-independent randomness amplification protocols. The properly interpreted $\epsilon$ parameter can potentially serve as a new characteristic of the human's heart from the perspective of medicine.}, archiveprefix = {arXiv}, doi = {10.3390/e23091182}, eprint = {2107.14630}, keywords = {Quantum Physics}, primaryclass = {quant-ph}, url = {https://ui.adsabs.harvard.edu/abs/2021Entrp..23.1182S}, }`

- Anubhav Chaturvedi, Máté. Farkas, and Victoria J. Wright. Characterising and bounding the set of quantum behaviours in contextuality scenarios.
*Quantum*, 5:484, 06 2021. doi:10.22331/q-2021-06-29-484

[BibTeX] [Abstract] [Download PDF]

The predictions of quantum theory resist generalised noncontextual explanations. In addition to the foundational relevance of this fact, the particular extent to which quantum theory violates noncontextuality limits available quantum advantage in communication and information processing. In the first part of this work, we formally define contextuality scenarios via prepare-and-measure experiments, along with the polytope of general contextual behaviours containing the set of quantum contextual behaviours. This framework allows us to recover several properties of set of quantum behaviours in these scenarios, including contextuality scenarios and associated noncontextuality inequalities that require for their violation the individual quantum preparation and measurement procedures to be mixed states and unsharp measurements. With the framework in place, we formulate novel semidefinite programming relaxations for bounding these sets of quantum contextual behaviours. Most significantly, to circumvent the inadequacy of pure states and projective measurements in contextuality scenarios, we present a novel unitary operator based semidefinite relaxation technique. We demonstrate the efficacy of these relaxations by obtaining tight upper bounds on the quantum violation of several noncontextuality inequalities and identifying novel maximally contextual quantum strategies. To further illustrate the versatility of these relaxations, we demonstrate $\textit{monogamy of preparation contextuality}$ in a tripartite setting, and present a secure semi-device independent quantum key distribution scheme powered by quantum advantage in parity oblivious random access codes.

`@Article{Chaturvedi2021, author = {Anubhav Chaturvedi and Máté Farkas and Victoria J Wright}, journal = {Quantum}, title = {Characterising and bounding the set of quantum behaviours in contextuality scenarios}, year = {2021}, issn = {2521-327X}, month = {06}, pages = {484}, volume = {5}, abstract = {The predictions of quantum theory resist generalised noncontextual explanations. In addition to the foundational relevance of this fact, the particular extent to which quantum theory violates noncontextuality limits available quantum advantage in communication and information processing. In the first part of this work, we formally define contextuality scenarios via prepare-and-measure experiments, along with the polytope of general contextual behaviours containing the set of quantum contextual behaviours. This framework allows us to recover several properties of set of quantum behaviours in these scenarios, including contextuality scenarios and associated noncontextuality inequalities that require for their violation the individual quantum preparation and measurement procedures to be mixed states and unsharp measurements. With the framework in place, we formulate novel semidefinite programming relaxations for bounding these sets of quantum contextual behaviours. Most significantly, to circumvent the inadequacy of pure states and projective measurements in contextuality scenarios, we present a novel unitary operator based semidefinite relaxation technique. We demonstrate the efficacy of these relaxations by obtaining tight upper bounds on the quantum violation of several noncontextuality inequalities and identifying novel maximally contextual quantum strategies. To further illustrate the versatility of these relaxations, we demonstrate $\textit{monogamy of preparation contextuality}$ in a tripartite setting, and present a secure semi-device independent quantum key distribution scheme powered by quantum advantage in parity oblivious random access codes.}, doi = {10.22331/q-2021-06-29-484}, groups = {Sainz}, publisher = {Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften}, url = {https://quantum-journal.org/papers/q-2021-06-29-484/pdf/}, }`

- Wooyeong Song, Marcin Wieśniak, Nana Liu, Marcin Pawłowski, Jinhyoung Lee, Jaewan Kim, and Jeongho Bang. Tangible reduction in learning sample complexity with large classical samples and small quantum system.
*Quantum Information Processing*, 20(8):Paper No. 275, 18, 2021. doi:10.1007/s11128-021-03217-7

[BibTeX] [Download PDF]`@Article{Song2021, author = {Song, Wooyeong and Wieśniak, Marcin and Liu, Nana and Pawłowski, Marcin and Lee, Jinhyoung and Kim, Jaewan and Bang, Jeongho}, journal = {Quantum {I}nformation {P}rocessing}, title = {Tangible reduction in learning sample complexity with large classical samples and small quantum system}, year = {2021}, issn = {1570-0755}, number = {8}, pages = {Paper No. 275, 18}, volume = {20}, doi = {10.1007/s11128-021-03217-7}, keywords = {81P68}, mrnumber = {4303621}, url = {https://link.springer.com/content/pdf/10.1007/s11128-021-03217-7.pdf}, }`

### 2020

- Karol Horodecki and Maciej Stankiewicz. Semi-device-independent quantum money.
*New Journal of Physics*, 22(2):23007, 2020. doi:10.1088/1367-2630/ab6872

[BibTeX] [Download PDF]`@Article{horodecki_semi-device-independent_2020, author = {Horodecki, Karol and Stankiewicz, Maciej}, journal = {New {J}ournal of {P}hysics}, title = {Semi-device-independent quantum money}, year = {2020}, issn = {1367-2630}, month = feb, number = {2}, pages = {023007}, volume = {22}, doi = {10.1088/1367-2630/ab6872}, url = {https://iopscience.iop.org/article/10.1088/1367-2630/ab6872}, urldate = {2020-04-22}, }`

- Marcin Pawłowski. Entropy in Foundations of Quantum Physics.
*Entropy*, 22(3):371, mar 2020. doi:10.3390/e22030371

[BibTeX] [Abstract] [Download PDF]

Entropy can be used in studies on foundations of quantum physics in many different ways, each of them using different properties of this mathematical object […]

`@article{pawlowski_entropy_2020, title = {Entropy in {Foundations} of {Quantum} {Physics}}, volume = {22}, issn = {1099-4300}, url = {https://www.mdpi.com/1099-4300/22/3/371}, doi = {10.3390/e22030371}, abstract = {Entropy can be used in studies on foundations of quantum physics in many different ways, each of them using different properties of this mathematical object [...]}, language = {en}, number = {3}, urldate = {2020-04-22}, journal = {Entropy}, author = {Pawłowski, Marcin}, month = mar, year = {2020}, pages = {371}, }`

- 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}, }`

- 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):32621, 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}, }`

- Anubhav Chaturvedi and Debashis Saha. Quantum prescriptions are more ontologically distinct than they are operationally distinguishable.
*Quantum*, 4:345, oct 2020. doi:10.22331/q-2020-10-21-345

[BibTeX] [Abstract] [Download PDF]

Based on an intuitive generalization of the Leibniz principle of `the identity of indiscernibles’, we introduce a novel ontological notion of classicality, called bounded ontological distinctness. Formulated as a principle, bounded ontological distinctness equates the distinguishability of a set of operational physical entities to the distinctness of their ontological counterparts. Employing three instances of two-dimensional quantum preparations, we demonstrate the violation of bounded ontological distinctness or excess ontological distinctness of quantum preparations, without invoking any additional assumptions. Moreover, our methodology enables the inference of tight lower bounds on the extent of excess ontological distinctness of quantum preparations. Similarly, we demonstrate excess ontological distinctness of quantum transformations, using three two-dimensional unitary transformations. However, to demonstrate excess ontological distinctness of quantum measurements, an additional assumption such as outcome determinism or bounded ontological distinctness of preparations is required. Moreover, we show that quantum violations of other well-known ontological principles implicate quantum excess ontological distinctness. Finally, to showcase the operational vitality of excess ontological distinctness, we introduce two distinct classes of communication tasks powered by excess ontological distinctness.

`@article{chaturvedi_quantum_2020, title = {Quantum prescriptions are more ontologically distinct than they are operationally distinguishable}, volume = {4}, issn = {2521-327X}, url = {https://quantum-journal.org/papers/q-2020-10-21-345/}, doi = {10.22331/q-2020-10-21-345}, abstract = {Based on an intuitive generalization of the Leibniz principle of `the identity of indiscernibles', we introduce a novel ontological notion of classicality, called bounded ontological distinctness. Formulated as a principle, bounded ontological distinctness equates the distinguishability of a set of operational physical entities to the distinctness of their ontological counterparts. Employing three instances of two-dimensional quantum preparations, we demonstrate the violation of bounded ontological distinctness or excess ontological distinctness of quantum preparations, without invoking any additional assumptions. Moreover, our methodology enables the inference of tight lower bounds on the extent of excess ontological distinctness of quantum preparations. Similarly, we demonstrate excess ontological distinctness of quantum transformations, using three two-dimensional unitary transformations. However, to demonstrate excess ontological distinctness of quantum measurements, an additional assumption such as outcome determinism or bounded ontological distinctness of preparations is required. Moreover, we show that quantum violations of other well-known ontological principles implicate quantum excess ontological distinctness. Finally, to showcase the operational vitality of excess ontological distinctness, we introduce two distinct classes of communication tasks powered by excess ontological distinctness.}, language = {en}, urldate = {2021-05-10}, journal = {Quantum}, author = {Chaturvedi, Anubhav and Saha, Debashis}, month = oct, year = {2020}, pages = {345}, }`

### 2019

- Piotr Mironowicz and Marcin Pawłowski. Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements.
*Physical Review A*, 100(3):30301, 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} }`

## arXiv preprints

### 2021

- Mariami Gachechiladze, Bartłomiej Bąk, Marcin Pawłowski, and Nikolai Miklin. Quantum Bell inequalities from Information Causality – tight for Macroscopic Locality.
*Arxiv:2103.05029 [quant-ph]*, mar 2021. arXiv: 2103.05029

[BibTeX] [Abstract] [Download PDF]

Quantum generalizations of Bell inequalities are analytical expressions of correlations observed in the Bell experiment that are used to explain or estimate the set of correlations that quantum theory allows. Unlike standard Bell inequalities, their quantum analogs are rare in the literature, as no known algorithm can be used to find them systematically. In this work, we present a family of quantum Bell inequalities in scenarios where the number of settings or outcomes can be arbitrarily high. We derive these inequalities from the principle of Information Causality, and thus, we do not assume the formalism of quantum mechanics. Considering the symmetries of the derived inequalities, we show that the latter give the necessary and sufficient condition for the correlations to comply with Macroscopic Locality. As a result, we conclude that the principle of Information Causality is strictly stronger than the principle of Macroscopic Locality in the subspace defined by these symmetries.

`@article{gachechiladze_quantum_2021, title = {Quantum {Bell} inequalities from {Information} {Causality} -- tight for {Macroscopic} {Locality}}, url = {http://arxiv.org/abs/2103.05029}, abstract = {Quantum generalizations of Bell inequalities are analytical expressions of correlations observed in the Bell experiment that are used to explain or estimate the set of correlations that quantum theory allows. Unlike standard Bell inequalities, their quantum analogs are rare in the literature, as no known algorithm can be used to find them systematically. In this work, we present a family of quantum Bell inequalities in scenarios where the number of settings or outcomes can be arbitrarily high. We derive these inequalities from the principle of Information Causality, and thus, we do not assume the formalism of quantum mechanics. Considering the symmetries of the derived inequalities, we show that the latter give the necessary and sufficient condition for the correlations to comply with Macroscopic Locality. As a result, we conclude that the principle of Information Causality is strictly stronger than the principle of Macroscopic Locality in the subspace defined by these symmetries.}, urldate = {2021-07-28}, journal = {arXiv:2103.05029 [quant-ph]}, author = {Gachechiladze, Mariami and Bąk, Bartłomiej and Pawłowski, Marcin and Miklin, Nikolai}, month = mar, year = {2021}, note = {arXiv: 2103.05029}, keywords = {Quantum Physics}, }`

- Anubhav Chaturvedi, Marcin Paw{l}owski, and Debashis Saha. Quantum description of reality is empirically incomplete.
*Arxiv e-prints*, pages arXiv:2110.13124, oct 2021.

[BibTeX] [Abstract] [Download PDF]

Empirical falsifiability of the predictions of physical theories is the cornerstone of the scientific method. Physical theories attribute empirically falsifiable operational properties to sets of physical preparations. A theory is said to be empirically complete if such properties allow for a not fine-tuned realist explanation, as properties of underlying probability distributions over states of reality. Such theories satisfy a family of equalities among fundamental operational properties, characterized exclusively by the number of preparations. Quantum preparations deviate from these equalities, and the maximal quantum deviation increases with the number of preparations. These deviations not only signify the incompleteness of the operational quantum formalism, but they simultaneously imply quantum over classical advantage in suitably constrained one-way communication tasks, highlighting the delicate interplay between the two.

`@Article{Chaturvedi2021, author = {Chaturvedi, Anubhav and Paw{\l}owski, Marcin and Saha, Debashis}, journal = {arXiv e-prints}, title = {Quantum description of reality is empirically incomplete}, year = {2021}, month = oct, pages = {arXiv:2110.13124}, abstract = {Empirical falsifiability of the predictions of physical theories is the cornerstone of the scientific method. Physical theories attribute empirically falsifiable operational properties to sets of physical preparations. A theory is said to be empirically complete if such properties allow for a not fine-tuned realist explanation, as properties of underlying probability distributions over states of reality. Such theories satisfy a family of equalities among fundamental operational properties, characterized exclusively by the number of preparations. Quantum preparations deviate from these equalities, and the maximal quantum deviation increases with the number of preparations. These deviations not only signify the incompleteness of the operational quantum formalism, but they simultaneously imply quantum over classical advantage in suitably constrained one-way communication tasks, highlighting the delicate interplay between the two.}, archiveprefix = {arXiv}, eid = {arXiv:2110.13124}, eprint = {2110.13124}, keywords = {Quantum Physics}, primaryclass = {quant-ph}, url = {https://ui.adsabs.harvard.edu/abs/2021arXiv211013124C}, }`

### 2020

- Wooyeong Song, Marcin Wieśniak, Nana Liu, Marcin Pawłowski, Jinhyoung Lee, Jaewan Kim, and Jeongho Bang. Tangible Reduction of Sample Complexity with Large Classical Samples and Small Quantum System.
*Arxiv:1905.05751 [quant-ph]*, jun 2020. arXiv: 1905.05751

[BibTeX] [Abstract] [Download PDF]

Quantum computation requires large classical datasets to be embedded into quantum states in order to exploit quantum parallelism. However, this embedding requires considerable resources. It would therefore be desirable to avoid it, if possible, for noisy intermediate-scale quantum (NISQ) implementation. Accordingly, we consider a classical-quantum hybrid architecture, which allows large classical input data, with a relatively small-scale quantum system. This hybrid architecture is used to implement an oracle. It is shown that in the presence of noise in the hybrid oracle, the effects of internal noise can cancel each other out and thereby improve the query success rate. It is also shown that such an immunity of the hybrid oracle to noise directly and tangibly reduces the sample complexity in the probably-approximately-correct learning framework. This NISQ-compatible learning advantage is attributed to the oracle’s ability to handle large input features.

`@article{song_tangible_2020, title = {Tangible {Reduction} of {Sample} {Complexity} with {Large} {Classical} {Samples} and {Small} {Quantum} {System}}, url = {http://arxiv.org/abs/1905.05751}, abstract = {Quantum computation requires large classical datasets to be embedded into quantum states in order to exploit quantum parallelism. However, this embedding requires considerable resources. It would therefore be desirable to avoid it, if possible, for noisy intermediate-scale quantum (NISQ) implementation. Accordingly, we consider a classical-quantum hybrid architecture, which allows large classical input data, with a relatively small-scale quantum system. This hybrid architecture is used to implement an oracle. It is shown that in the presence of noise in the hybrid oracle, the effects of internal noise can cancel each other out and thereby improve the query success rate. It is also shown that such an immunity of the hybrid oracle to noise directly and tangibly reduces the sample complexity in the probably-approximately-correct learning framework. This NISQ-compatible learning advantage is attributed to the oracle's ability to handle large input features.}, urldate = {2021-07-28}, journal = {arXiv:1905.05751 [quant-ph]}, author = {Song, Wooyeong and Wieśniak, Marcin and Liu, Nana and Pawłowski, Marcin and Lee, Jinhyoung and Kim, Jaewan and Bang, Jeongho}, month = jun, year = {2020}, note = {arXiv: 1905.05751}, keywords = {Quantum Physics}, }`

## Group members

###### Get to know the people behind ICTQT.

## Former members

__Keywords:__ quantum cryptography, random number generation, cryptoanalysis, quantum communication, quantum key distribution, device-independent protocols.