Multiphoton Quantum Optics for Quantum Information Group

2022

1. Massimiliano Incudini, Fabio Tarocco, Riccardo Mengoni, Alessandra Di Pierro, and Antonio Mandarino. Computing graph edit distance on quantum devices. Quantum Machine Intelligence, 4(2):1-21, 2022. acknowledgment to ICTQT IRAP project included
   [BibTeX]

   @article{incudini2022computing,
     title={Computing graph edit distance on quantum devices},
     author={Incudini, Massimiliano and Tarocco, Fabio and Mengoni, Riccardo and Di Pierro, Alessandra and Mandarino, Antonio},
     journal={Quantum Machine Intelligence},
     volume={4},
     number={2},
     pages={1--21},
     year={2022},
     publisher={Springer},
     eprint = {arXiv:2111.10183},
     note = {acknowledgment to ICTQT IRAP project included}
   }

2. Antonio Mandarino. Quantum Thermal Amplifiers with Engineered Dissipation. Entropy, 24(8):1031, jul 2022. acknowledgment to ICTQT IRAP project included doi:10.3390/e24081031
   [BibTeX] [Download PDF]

   @article{Mandarino_2022,
     doi = {10.3390/e24081031},
       url = {https://doi.org/10.3390/e24081031},
       year = 2022,
     month = jul,
       publisher = {{MDPI} {AG}},
       volume = {24},
       number = {8},
       pages = {1031},
       author = {Antonio Mandarino},
       title = {Quantum Thermal Amplifiers with Engineered Dissipation},
       journal = {Entropy},
       eprint = {arXiv:2208.12620},
     note = {acknowledgment to ICTQT IRAP project included}
   }

3. Marcin Karczewski, Giovanni Scala, Antonio Mandarino, Ana Belén Sainz, and Marek Żukowski. Avenues to generalising Bell inequalities. Journal of Physics A: Mathematical and Theoretical, 55:384011, 2022. doi:10.1088/1751-8121/ac8a28
   [BibTeX]

   @article{karczewski2022avenues,
     title={Avenues to generalising Bell inequalities},
     author={Karczewski, Marcin and Scala, Giovanni and Mandarino, Antonio and Sainz, Ana Bel{\'e}n and {\.Z}ukowski, Marek},
     journal={Journal of Physics A: Mathematical and Theoretical},
     year={2022},
     volume={55},
     pages={384011},
     publisher={IOP Publishing},
     doi={10.1088/1751-8121/ac8a28}
   }

4. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Żukowski. Remarks about Bell-nonclassicality of a single photon. Physics Letters A, 435:128031, 2022. doi:https://doi.org/10.1016/j.physleta.2022.128031
   [BibTeX] [Abstract] [Download PDF]
   

   We discuss the interferometric scheme put forward by Tan, Walls, and Collett (TWC) that claims to reveal Bell non-classicality of a single photon. We show that the violation of local realism they report hinges on an additional assumption about hidden variables. Without it, one can construct a classical model that correctly predicts all the probabilities of the TWC scheme. To illustrate this, we construct a proper Bell inequality, devoid of additional assumptions, that is not violated by the TWC setup. We then show a modification of the interferometric scheme, consisting in making the amplitude of auxiliary fields tunable, that enables the Bell violation. Finally, we present an alternative point of view on the shortcomings of the original TWC analysis, arguing that it effectively treats the weak coherent states classically.

   @article{DAS2022128031,
    title = {Remarks about {Bell}-nonclassicality of a single photon},
    journal = {Physics Letters A},
    volume = {435},
    pages = {128031},
    year = {2022},
    issn = {0375-9601},
    doi = {https://doi.org/10.1016/j.physleta.2022.128031},
    url = {https://www.sciencedirect.com/science/article/pii/S037596012200113X},
    author = {Tamoghna Das and Marcin Karczewski and Antonio Mandarino and Marcin Markiewicz and Bianka Woloncewicz and Marek Żukowski},
    keywords = {Bell's theorem, Single photon, Local hidden variable model},
    abstract = {We discuss the interferometric scheme put forward by Tan, Walls, and Collett (TWC) that claims to reveal Bell non-classicality of a single photon. We show that the violation of local realism they report hinges on an additional assumption about hidden variables. Without it, one can construct a classical model that correctly predicts all the probabilities of the TWC scheme. To illustrate this, we construct a proper Bell inequality, devoid of additional assumptions, that is not violated by the TWC setup. We then show a modification of the interferometric scheme, consisting in making the amplitude of auxiliary fields tunable, that enables the Bell violation. Finally, we present an alternative point of view on the shortcomings of the original TWC analysis, arguing that it effectively treats the weak coherent states classically.},
    urldate={2022-03-31}
   }

5. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Zukowski. Comment on `Single particle nonlocality with completely independent reference states’. New Journal of Physics, 24(3):038001, mar 2022. doi:10.1088/1367-2630/ac55b1
   [BibTeX] [Abstract] [Download PDF]
   

   We comment on the purported violation of local realism, by a single photon induced correlations between homodyne detectors, which one can find in: (2008) New J. Phys. 10 113024 [arXiv:0807.0109]. The claim is erroneous, due to a calculational mistake. As the result is the basis of other claims in the paper, they are unsubstantiated.

   @article{Das2022,
     title = {Comment on `{Single} particle nonlocality with completely independent reference states'},
     author = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and Zukowski, Marek},
     doi = {10.1088/1367-2630/ac55b1},
     url = {https://doi.org/10.1088/1367-2630/ac55b1},
     year = 2022,
     month = mar,
     publisher = {{IOP} Publishing},
     volume = {24},
     number = {3},
     pages = {038001},
     journal = {New Journal of Physics},
     abstract = {We comment on the purported violation of local realism, by a single photon induced correlations between homodyne detectors, which one can find in: (2008) New J. Phys. 10 113024 [arXiv:0807.0109]. The claim is erroneous, due to a calculational mistake. As the result is the basis of other claims in the paper, they are unsubstantiated.},
     eprint = {arXiv:2107.07951},
     urldate={2022-03-31}
   }

6. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Żukowski. Wave–particle complementarity: detecting violation of local realism with photon-number resolving weak-field homodyne measurements. New Journal of Physics, 24(3):033017, 2022. doi:10.1088/1367-2630/ac54c8
   [BibTeX] [Download PDF]

   @article{das2022wave,
     title={Wave--particle complementarity: detecting violation of local realism with photon-number resolving weak-field homodyne measurements},
     author={Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and {\.Z}ukowski, Marek},
     journal={New Journal of Physics},
     volume={24},
     number={3},
     pages={033017},
     year={2022},
     publisher={IOP Publishing},
     url={https://doi.org/10.1088/1367-2630/ac54c8},
     doi={10.1088/1367-2630/ac54c8},
     urldate={2022-03-31},
     eprint = {arXiv:2104.10703}
   }

7. Karol Horodecki, Marek Winczewski, and Siddhartha Das. Fundamental limitations on the device-independent quantum conference key agreement. Physical Review A, 105(2), feb 2022. doi:10.1103/physreva.105.022604
   [BibTeX] [Download PDF]

   @article{Horodecki_2022,
     doi = {10.1103/physreva.105.022604},
     url = {http://dx.doi.org/10.1103/PhysRevA.105.022604},
     year = 2022,
     month = feb,
     publisher = {American Physical Society ({APS})},
     volume = {105},
     number = {2},
     author = {Karol Horodecki and Marek Winczewski and Siddhartha Das},
     title = {Fundamental limitations on the device-independent quantum conference key agreement},
     journal = {Physical Review A}
   }

8. Konrad Schlichtholz, Bianka Woloncewicz, and Marek Żukowski. Simplified quantum optical Stokes observables and Bell’s theorem. Scientific reports, 12(1):1-9, 2022. doi:https://doi.org/10.1038/s41598-022-14232-8
   [BibTeX] [Download PDF]

   @article{schlichtholz2021simplified,
     title={Simplified quantum optical Stokes observables and Bell’s theorem},
     author={Schlichtholz, Konrad and Woloncewicz, Bianka and {\.Z}ukowski, Marek},
     journal={Scientific reports},
     volume={12},
     number={1},
     pages={1--9},
     year={2022},
     publisher={Nature Publishing Group},
    doi={https://doi.org/10.1038/s41598-022-14232-8},
    url={https://www.nature.com/articles/s41598-022-14232-8}
   }

2021

1. Siddhartha Das, Stefan Bäuml, Marek Winczewski, and Karol Horodecki. Universal Limitations on Quantum Key Distribution over a Network. Physical Review X, 11(4), oct 2021. doi:10.1103/physrevx.11.041016
   [BibTeX] [Download PDF]

   @article{Das_2021,
     doi = {10.1103/physrevx.11.041016},
       url = {http://dx.doi.org/10.1103/physrevx.11.041016},
       year = 2021,
     month = oct,
       publisher = {American Physical Society ({APS})},
       volume = {11},
       number = {4},
       author = {Siddhartha Das and Stefan Bäuml and Marek Winczewski and Karol Horodecki},
       title = {Universal Limitations on Quantum Key Distribution over a Network},
       journal = {Physical Review X}
   }

2. Marek Żukowski and Marcin Markiewicz. Physics and Metaphysics of Wigner’s Friends: Even Performed Premeasurements Have No Results. Physical Review Letters, 126(13):130402, apr 2021. doi:10.1103/PhysRevLett.126.130402
   [BibTeX] [Download PDF]

   @Article{zukowski_physics_2021,
     author     = {Żukowski, Marek and Markiewicz, Marcin},
     journal    = {Physical {R}eview {L}etters},
     title      = {Physics and {Metaphysics} of {Wigner}’s {Friends}: {Even} {Performed} {Premeasurements} {Have} {No} {Results}},
     year       = {2021},
     issn       = {0031-9007, 1079-7114},
     month      = apr,
     number     = {13},
     pages      = {130402},
     volume     = {126},
     doi        = {10.1103/PhysRevLett.126.130402},
     language   = {en},
     shorttitle = {Physics and {Metaphysics} of {Wigner}’s {Friends}},
     url        = {https://link.aps.org/doi/10.1103/PhysRevLett.126.130402},
     urldate    = {2021-05-10},
   }

3. Konrad Schlichtholz, Bianka Woloncewicz, and Marek Żukowski. Nonclassicality of bright Greenberger-Horne-Zeilinger–like radiation of an optical parametric source. Physical Review A, 103(4):042226, apr 2021. doi:10.1103/PhysRevA.103.042226
   [BibTeX] [Download PDF]

   @Article{schlichtholz_nonclassicality_2021,
     author   = {Schlichtholz, Konrad and Woloncewicz, Bianka and Żukowski, Marek},
     journal  = {Physical {R}eview {A}},
     title    = {Nonclassicality of bright {Greenberger}-{Horne}-{Zeilinger}–like radiation of an optical parametric source},
     year     = {2021},
     issn     = {2469-9926, 2469-9934},
     month    = apr,
     number   = {4},
     pages    = {042226},
     volume   = {103},
     doi      = {10.1103/PhysRevA.103.042226},
     language = {en},
     url      = {https://link.aps.org/doi/10.1103/PhysRevA.103.042226},
     urldate  = {2021-07-28},
   }

4. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Żukowski. Can single photon excitation of two spatially separated modes lead to a violation of Bell inequality via weak-field homodyne measurements?. New Journal of Physics, 23(7):073042, jul 2021. doi:10.1088/1367-2630/ac0ffe
   [BibTeX] [Abstract] [Download PDF]
   

   We reconsider the all-optical weak homodyne-measurement based experimental schemes aimed at revealing Bell nonclassicality (‘nonlocality’) of a single photon. We focus on the schemes put forward by Tan et al (TWC, 1991) and Hardy (1994). In our previous work we show that the TWC experiment can be described by a local hidden variable model, hence the claimed nonclassicality is apparent. The nonclassicality proof proposed by Hardy remains impeccable. We investigate which feature of the Hardy’s approach is crucial to disclose the nonclassicality. There are consequential differences between TWC and Hardy setups: (i) the initial state of Hardy is a superposition of a single photon excitation with vacuum in one of the input modes of a 50-50 beamsplitter. In the TWC case there is no vacuum component. (ii) In the final measurements of Hardy’s proposal the local settings are specified by the presence or absence of a local oscillator field (on/off). In the TWC case the auxiliary fields are constant, only phases are varied. We show that in Hardy’s setup the violation of local realism occurs due to the varying strength of the local oscillators. Still, one does not need to operate in the fully on/off detection scheme. Thus, the nonclassicality in a Hardy-like setup cannot be attributed to the single-photon state alone. It is a consequence of its interference with the photons from auxiliary local fields. Neither can it be attributed to the joint state of the single photon excitation and the local oscillator modes, as this state is measurement setting dependent. Despite giving spurious violations of local realism, the TWC scheme can serve as an entanglement indicator, for the TWC state. Nevertheless an analogue indicator based on intensity rates rather than just intensities overperforms it.

   @Article{Das2021a,
     author        = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and Żukowski, Marek},
     journal       = {New Journal of Physics},
     title         = {Can single photon excitation of two spatially separated modes lead to a violation of {B}ell inequality via weak-field homodyne measurements?},
     year          = {2021},
     month         = jul,
     number        = {7},
     pages         = {073042},
     volume        = {23},
     abstract      = {We reconsider the all-optical weak homodyne-measurement based         experimental schemes aimed at revealing Bell nonclassicality         ('nonlocality') of a single photon. We focus on the schemes put         forward by Tan et al (TWC, 1991) and Hardy (1994). In our         previous work we show that the TWC experiment can be described         by a local hidden variable model, hence the claimed         nonclassicality is apparent. The nonclassicality proof proposed         by Hardy remains impeccable. We investigate which feature of the         Hardy's approach is crucial to disclose the nonclassicality.         There are consequential differences between TWC and Hardy         setups: (i) the initial state of Hardy is a superposition of a         single photon excitation with vacuum in one of the input modes         of a 50-50 beamsplitter. In the TWC case there is no vacuum         component. (ii) In the final measurements of Hardy's proposal         the local settings are specified by the presence or absence of a         local oscillator field (on/off). In the TWC case the auxiliary         fields are constant, only phases are varied. We show that in         Hardy's setup the violation of local realism occurs due to the         varying strength of the local oscillators. Still, one does not         need to operate in the fully on/off detection scheme. Thus, the         nonclassicality in a Hardy-like setup cannot be attributed to         the single-photon state alone. It is a consequence of its         interference with the photons from auxiliary local fields.         Neither can it be attributed to the joint state of the single         photon excitation and the local oscillator modes, as this state         is measurement setting dependent. Despite giving spurious         violations of local realism, the TWC scheme can serve as an         entanglement indicator, for the TWC state. Nevertheless an         analogue indicator based on intensity rates rather than just         intensities overperforms it.},
     archiveprefix = {arXiv},
     doi           = {10.1088/1367-2630/ac0ffe},
     eid           = {073042},
     eprint        = {2102.06689},
     keywords      = {nonclassicality of single photon excitation, Bell inequalities, homodyne measurement, mode entanglement, entanglement witness, operators based on rates, Quantum Physics},
     primaryclass  = {quant-ph},
     url           = {https://ui.adsabs.harvard.edu/abs/2021NJPh...23g3042D}
   }

2020

1. Armin Tavakoli, Marek Żukowski, and Časlav Brukner. Does violation of a Bell inequality always imply quantum advantage in a communication complexity problem?. Quantum, 4:316, sep 2020. doi:10.22331/q-2020-09-07-316
   [BibTeX] [Abstract] [Download PDF]
   

   Quantum correlations which violate a Bell inequality are presumed to power better-than-classical protocols for solving communication complexity problems (CCPs). How general is this statement? We show that violations of correlation-type Bell inequalities allow advantages in CCPs, when communication protocols are tailored to emulate the Bell no-signaling constraint (by not communicating measurement settings). Abandonment of this restriction on classical models allows us to disprove the main result of, inter alia, \textbackslashcite\BZ02\; we show that quantum correlations obtained from these communication strategies assisted by a small quantum violation of the CGLMP Bell inequalities do not imply advantages in any CCP in the input/output scenario considered in the reference. More generally, we show that there exists quantum correlations, with nontrivial local marginal probabilities, which violate the I 3322 Bell inequality, but do not enable a quantum advantange in any CCP, regardless of the communication strategy employed in the quantum protocol, for a scenario with a fixed number of inputs and outputs

   @Article{tavakoli_does_2020,
     author   = {Tavakoli, Armin and Żukowski, Marek and Brukner, Časlav},
     journal  = {Quantum},
     title    = {Does violation of a {Bell} inequality always imply quantum advantage in a communication complexity problem?},
     year     = {2020},
     issn     = {2521-327X},
     month    = sep,
     pages    = {316},
     volume   = {4},
     abstract = {Quantum correlations which violate a Bell inequality are presumed to power better-than-classical protocols for solving communication complexity problems (CCPs). How general is this statement? We show that violations of correlation-type Bell inequalities allow advantages in CCPs, when communication protocols are tailored to emulate the Bell no-signaling constraint (by not communicating measurement settings). Abandonment of this restriction on classical models allows us to disprove the main result of, inter alia, {\textbackslash}cite\{BZ02\}; we show that quantum correlations obtained from these communication strategies assisted by a small quantum violation of the CGLMP Bell inequalities do not imply advantages in any CCP in the input/output scenario considered in the reference. More generally, we show that there exists quantum correlations, with nontrivial local marginal probabilities, which violate the I 3322 Bell inequality, but do not enable a quantum advantange in any CCP, regardless of the communication strategy employed in the quantum protocol, for a scenario with a fixed number of inputs and outputs},
     doi      = {10.22331/q-2020-09-07-316},
     language = {en},
     url      = {https://quantum-journal.org/papers/q-2020-09-07-316/},
     urldate  = {2021-05-10},
   }

2. Saptarshi Roy, Tamoghna Das, and Aditi Sen(De). Computable genuine multimode entanglement measure: Gaussian versus non-Gaussian. Physical Review A, 102(1):012421, jul 2020. doi:10.1103/PhysRevA.102.012421
   [BibTeX] [Download PDF]

   @Article{roy_computable_2020,
     author     = {Roy, Saptarshi and Das, Tamoghna and Sen(De), Aditi},
     journal    = {Physical {R}eview {A}},
     title      = {Computable genuine multimode entanglement measure: {Gaussian} versus non-{Gaussian}},
     year       = {2020},
     issn       = {2469-9926, 2469-9934},
     month      = jul,
     number     = {1},
     pages      = {012421},
     volume     = {102},
     doi        = {10.1103/PhysRevA.102.012421},
     language   = {en},
     shorttitle = {Computable genuine multimode entanglement measure},
     url        = {https://link.aps.org/doi/10.1103/PhysRevA.102.012421},
     urldate    = {2021-05-10},
   }

2019

1. Junghee Ryu, Bianka Woloncewicz, Marcin Marciniak, Marcin Wieśniak, and Marek Żukowski. General mapping of multiqudit entanglement conditions to nonseparability indicators for quantum-optical fields. Physical Review Research, 1(3):032041, dec 2019. doi:10.1103/PhysRevResearch.1.032041
   [BibTeX] [Download PDF]

   @Article{ryu_general_2019,
     author   = {Ryu, Junghee and Woloncewicz, Bianka and Marciniak, Marcin and Wieśniak, Marcin and Żukowski, Marek},
     journal  = {Physical {R}eview {R}esearch},
     title    = {General mapping of multiqudit entanglement conditions to nonseparability indicators for quantum-optical fields},
     year     = {2019},
     issn     = {2643-1564},
     month    = dec,
     number   = {3},
     pages    = {032041},
     volume   = {1},
     doi      = {10.1103/PhysRevResearch.1.032041},
     groups   = {Zukowski},
     language = {en},
     url      = {https://link.aps.org/doi/10.1103/PhysRevResearch.1.032041},
     urldate  = {2020-05-13},
   }

2. Antonio Mandarino, Karl Joulain, Melisa Domínguez Gómez, and Bruno Bellomo. Thermal transistor effect in quantum systems. Physcal Review Applied 16, 034026 (2021), feb 2019. doi:10.1103/PhysRevApplied.16.034026
   [BibTeX] [Abstract] [Download PDF]
   

   We study a quantum system composed of three interacting qubits, each coupled to a different thermal reservoir. We show how to engineer it in order to build a quantum device that is analogous to an electronic bipolar transistor. We outline how the interaction among the qubits plays a crucial role for the appearance of the effect, also linking it to the characteristics of system-bath interactions that govern the decoherence and dissipation mechanism of the system. By comparing with previous proposals, the model considered here extends the regime of parameters where the transistor effect shows up and its robustness with respect to small variations of the coupling parameters. Moreover, our model appears to be more realistic and directly connected in terms of potential implementations to feasible setups in the domain of quantum spin chains and molecular nanomagnets.

   @Article{Mandarino2019,
     author        = {Antonio Mandarino and Karl Joulain and Melisa Domínguez Gómez and Bruno Bellomo},
     journal       = {Physcal {R}eview {A}pplied 16, 034026 (2021)},
     title         = {Thermal transistor effect in quantum systems},
     year          = {2019},
     month         = feb,
     abstract      = {We study a quantum system composed of three interacting qubits, each coupled to a different thermal reservoir. We show how to engineer it in order to build a quantum device that is analogous to an electronic bipolar transistor. We outline how the interaction among the qubits plays a crucial role for the appearance of the effect, also linking it to the characteristics of system-bath interactions that govern the decoherence and dissipation mechanism of the system. By comparing with previous proposals, the model considered here extends the regime of parameters where the transistor effect shows up and its robustness with respect to small variations of the coupling parameters. Moreover, our model appears to be more realistic and directly connected in terms of potential implementations to feasible setups in the domain of quantum spin chains and molecular nanomagnets.},
     archiveprefix = {arXiv},
     doi           = {10.1103/PhysRevApplied.16.034026},
     eprint        = {1902.01309},
     file          = {:Mandarino2019 - Thermal Transistor Effect in Quantum Systems.pdf:PDF},
     groups        = {Zukowski},
     keywords      = {quant-ph},
     primaryclass  = {quant-ph},
     url           = {https://journals.aps.org/prapplied/pdf/10.1103/PhysRevApplied.16.034026},
   }

2018

1. Arijit Dutta, Tschang-Uh Nahm, Jinhyoung Lee, and Marek Żukowski. Geometric extension of Clauser–Horne inequality to more qubits. New Journal of Physics, 20(9):093006, sep 2018. doi:10.1088/1367-2630/aadc78
   [BibTeX] [Download PDF]

   @Article{dutta_geometric_2018,
     author  = {Dutta, Arijit and Nahm, Tschang-Uh and Lee, Jinhyoung and Żukowski, Marek},
     journal = {New {J}ournal of {P}hysics},
     title   = {Geometric extension of {Clauser}–{Horne} inequality to more qubits},
     year    = {2018},
     issn    = {1367-2630},
     month   = sep,
     number  = {9},
     pages   = {093006},
     volume  = {20},
     doi     = {10.1088/1367-2630/aadc78},
     groups  = {Zukowski},
     url     = {https://iopscience.iop.org/article/10.1088/1367-2630/aadc78},
     urldate = {2020-04-22},
   }

2022

1. Saverio Monaco, Oriel Kiss, Antonio Mandarino, Sofia Vallecorsa, and Michele Grossi. Quantum phase detection generalisation from marginal quantum neural network models. , 2022. doi:10.48550/ARXIV.2208.08748
   [BibTeX] [Download PDF]

   @article{QCNN_ANNNI,
     doi = {10.48550/ARXIV.2208.08748},
       url = {https://arxiv.org/abs/2208.08748},
       author = {Monaco, Saverio and Kiss, Oriel and Mandarino, Antonio and Vallecorsa, Sofia and Grossi, Michele},
       keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences},
       title = {Quantum phase detection generalisation from marginal quantum neural network models},
       publisher = {arXiv},
       year = {2022},
       copyright = {arXiv.org perpetual, non-exclusive license}
   }

2. Michele Grossi, Oriel Kiss, Francesco De Luca, Carlo Zollo, Ian Gremese, and Antonio Mandarino. Finite-size criticality in fully connected spin models on superconducting quantum hardware. , 2022. doi:10.48550/ARXIV.2208.02731
   [BibTeX] [Download PDF]

   @article{VQE_LMG,
     doi = {10.48550/ARXIV.2208.02731},
       url = {https://arxiv.org/abs/2208.02731},
       author = {Grossi, Michele and Kiss, Oriel and De Luca, Francesco and Zollo, Carlo and Gremese, Ian and Mandarino, Antonio},
       keywords = {Quantum Physics (quant-ph), Statistical Mechanics (cond-mat.stat-mech), FOS: Physical sciences, FOS: Physical sciences},
       title = {Finite-size criticality in fully connected spin models on superconducting quantum hardware},
       publisher = {arXiv},
       year = {2022},
       copyright = {arXiv.org perpetual, non-exclusive license}
   }

3. Konrad Schlichtholz, Antonio Mandarino, and Marek Żukowski. Bosonic fields in states with undefined particle numbers possess detectable non-contextuality features, plus more . arXiv e-prints, pages arXiv.2205.09440, may 2022.
   [BibTeX] [Abstract] [Download PDF]
   

   Most of the paradoxical, for the classical intuition, features of quantum theory were formulated for situations which involve a fixed number of particles. While one can now find a formulation of Bell’s theorem for quantum fields, a Kochen-Specker-type reasoning is usually formulated for just one particle, or like in the case of Peres-Mermin square for two. A question emerges. Is it possible to formulate a contextuality proof for situation in which the numbers of particles are fundamentally undefined? We address this problem for bosonic fields. We introduce a representation of the su(2) algebra in terms of boson number states in two modes that allows us to assess nonclassicality of states of bosonic fields. As a figure of merit of a nonclassical behaviour we analyze first of all contextuality, and we show that the introduced observables are handy and efficient to reveal violation of local realism, and to formulate entanglement indicators. We construct a method which extends the Kochen-Specker contextuality to bosonic quantum fields. A form of an inequality is derived using a suitable version of the Peres-Mermin square. The entanglement indicators use a witness built with specially defined Pauli-like observables. Finally, Bell-nonclassicality is discussed: an inequality that involves the expectation values of pairs of the Pauli-like operators is presented. The introduced indicators are shown to be effective, e.g. they reveal nonclassicality in situaations involving undefined boson numbers. This is shown via quantum optical examples of the 2×2 bright squeezed vacuum state, and a recently discussed bright-GHZ state resulting from multiple three photon emissions in a parametric process.

   @Article{Schlichtholz2022,
     author        = { Schlichtholz, Konrad and Mandarino, Antonio and Żukowski, Marek },
     journal       = {arXiv e-prints},
     title         = { Bosonic fields in states with undefined particle numbers possess detectable non-contextuality features, plus more },
     year          = {2022},
     month         = may,
     pages         = {arXiv.2205.09440},
     abstract      = { Most of the paradoxical, for the classical intuition, features of quantum theory were formulated for situations which involve a fixed number of particles. While one can now find a formulation of Bell's theorem for quantum fields, a Kochen-Specker-type reasoning is usually formulated for just one particle, or like in the case of Peres-Mermin square for two. A question emerges. Is it possible to formulate a contextuality proof for situation in which the numbers of particles are fundamentally undefined? We address this problem for bosonic fields. We introduce a representation of the su(2) algebra in terms of boson number states in two modes that allows us to assess nonclassicality of states of bosonic fields. As a figure of merit of a nonclassical behaviour we analyze first of all contextuality, and we show that the introduced observables are handy and efficient to reveal violation of local realism, and to formulate entanglement indicators. We construct a method which extends the Kochen-Specker contextuality to bosonic quantum fields. A form of an inequality is derived using a suitable version of the Peres-Mermin square. The entanglement indicators use a witness built with specially defined Pauli-like observables. Finally, Bell-nonclassicality is discussed: an inequality that involves the expectation values of pairs of the Pauli-like operators is presented. The introduced indicators are shown to be effective, e.g. they reveal nonclassicality in situaations involving undefined boson numbers. This is shown via quantum optical examples of the 2×2 bright squeezed vacuum state, and a recently discussed bright-GHZ state resulting from multiple three photon emissions in a parametric process. },
     archiveprefix = {arXiv},
     eid           = {arXiv.2205.09440},
     eprint        = {2205.09440},
     keywords      = {Quantum Physics, Physical sciences },
     primaryclass  = {quant-ph},
     url           = {https://arxiv.org/abs/2205.09440},
   }

4. Tomasz Linowski, Konrad Schlichtholz, and Łukasz Rudnicki. A formal relation between Pegg-Barnett and Paul quantum phase frameworks. arXiv e-prints, pages arXiv.2205.09481, may 2022.
   [BibTeX] [Abstract] [Download PDF]
   

   The problem of defining a Hermitian quantum phase operator is nearly as old as quantum mechanics itself. Throughout the years, a number of solutions was proposed, ranging from abstract operator formalisms to phase-space methods. In this work, we connect two of the most prominent approaches: Pegg-Barnett and Paul formalisms, by proving that the Paul formalism is equivalent to the Pegg-Barnett formalism applied to an infinitely amplified state. Our findings fill in a conceptual gap in the understanding of the quantum phase problem.

   @Article{Linowski2022,
     author        = {Linowski, Tomasz and Schlichtholz, Konrad and Rudnicki, Łukasz},
     journal       = {arXiv e-prints},
     title         = {A formal relation between Pegg-Barnett and Paul quantum phase frameworks},
     year          = {2022},
     month         = may,
     pages         = {arXiv.2205.09481},
     abstract      = {The problem of defining a Hermitian quantum phase operator is nearly as old as quantum mechanics itself. Throughout the years, a number of solutions was proposed, ranging from abstract operator formalisms to phase-space methods. In this work, we connect two of the most prominent approaches: Pegg-Barnett and Paul formalisms, by proving that the Paul formalism is equivalent to the Pegg-Barnett formalism applied to an infinitely amplified state. Our findings fill in a conceptual gap in the understanding of the quantum phase problem.},
     archiveprefix = {arXiv},
     eid           = {arXiv.2205.09481},
     eprint        = {2205.09481},
     keywords      = {Quantum Physics, Physical sciences},
     primaryclass  = {quant-ph},
     url           = {https://arxiv.org/abs/2205.09481},
   }

5. Jay Lawrence, Marcin Markiewicz, and Marek Żukowski. Relative facts do not exist. Relational Quantum Mechanics is Incompatible with Quantum Mechanics. arXiv preprint arXiv:2208.11793, 2022.
   [BibTeX]

   @article{Lawrence22RQM,
     title={Relative facts do not exist. {Relational Quantum Mechanics is Incompatible with Quantum Mechanics}},
     author={Lawrence, Jay and Markiewicz, Marcin and Żukowski, Marek},
     journal={arXiv preprint   arXiv:2208.11793},
     year={2022}
   }

2021

1. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Żukowski. No-go for device independent protocols with Tan-Walls-Collett `nonlocality of a single photon’. arXiv:2102.03254 [quant-ph], feb 2021. arXiv: 2102.03254
   [BibTeX] [Abstract] [Download PDF]
   

   We investigate the interferometric scheme put forward by Tan, Walls and Collett [Phys. Rev. Lett. \\textbackslashbf 66\, 256 (1991)] that aims to reveal Bell non-classicality of a single photon. By providing a local hidden variable model that reproduces their results, we decisively refute this claim. In particular, this means that the scheme cannot be used in device-independent protocols.

   @article{das_no-go_2021,
     title = {No-go for device independent protocols with {Tan}-{Walls}-{Collett} `nonlocality of a single photon'},
     url = {http://arxiv.org/abs/2102.03254},
     abstract = {We investigate the interferometric scheme put forward by Tan, Walls and Collett [Phys. Rev. Lett. \{{\textbackslash}bf 66\}, 256 (1991)] that aims to reveal Bell non-classicality of a single photon. By providing a local hidden variable model that reproduces their results, we decisively refute this claim. In particular, this means that the scheme cannot be used in device-independent protocols.},
     urldate = {2021-07-28},
     journal = {arXiv:2102.03254 [quant-ph]},
     author = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and Żukowski, Marek},
     month = feb,
     year = {2021},
     note = {arXiv: 2102.03254},
     keywords = {Quantum Physics},
   }

2. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Zukowski. Can single photon excitation of two spatially separated modes lead to a violation of Bell inequality via homodyne measurements?. arXiv:2102.06689 [quant-ph], feb 2021. arXiv: 2102.06689
   [BibTeX] [Abstract] [Download PDF]
   

   We reconsider the all-optical homodyne-measurement based experimental schemes that aim to reveal Bell nonclassicality of a single photon, often termed `nonlocality’. We focus on the schemes put forward by Tan, Walls and Collett (TWC, 1991) and Hardy (1994). In the light of our previous work the Tan, Walls and Collett setup can be described by a precise local hidden variable model, hence the claimed nonclassicality of this proposal is apparent, whereas the nonclassicality proof proposed by Hardy is impeccable. In this work we resolve the following problem: which feature of the Hardy’s approach is crucial for its successful confirmation of nonclassicality. The scheme of Hardy differs from the Tan, Walls and Collett setup in two aspects. (i) It introduces a superposition of a single photon excitation with vacuum as the initial state of one of the input modes of a 50-50 beamsplitter, which creates the superposition state of two separable (exit) modes under investigation. (ii) In the final measurements Hardy’s proposal utilises a varying strengths of the local oscillator fields, whereas in the TWC case they are constant. In fact the local oscillators in Hardy’s scheme are either on or off (the local setting is specified by the presence or absence of the local auxiliary field). We show that it is the varying strength of the local oscillators, from setting to setting, which is the crucial feature enabling violation of local realism in the Hardy setup, whereas it is not necessary to use initial superposition of a single photon excitation with vacuum as the initial state of the input mode. Neither one needs to operate in the fully on/off detection scheme. Despite the failure of the Tan, Walls and Collett scheme in proving Bell nonclassicality, we show that their scheme can serve as an entanglement indicator.

   @article{das_can_2021,
     title = {Can single photon excitation of two spatially separated modes lead to a violation of {Bell} inequality via homodyne measurements?},
     author = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and Zukowski, Marek},
     url = {http://arxiv.org/abs/2102.06689},
     abstract = {We reconsider the all-optical homodyne-measurement based experimental schemes that aim to reveal Bell nonclassicality of a single photon, often termed `nonlocality'. We focus on the schemes put forward by Tan, Walls and Collett (TWC, 1991) and Hardy (1994). In the light of our previous work the Tan, Walls and Collett setup can be described by a precise local hidden variable model, hence the claimed nonclassicality of this proposal is apparent, whereas the nonclassicality proof proposed by Hardy is impeccable. In this work we resolve the following problem: which feature of the Hardy's approach is crucial for its successful confirmation of nonclassicality. The scheme of Hardy differs from the Tan, Walls and Collett setup in two aspects. (i) It introduces a superposition of a single photon excitation with vacuum as the initial state of one of the input modes of a 50-50 beamsplitter, which creates the superposition state of two separable (exit) modes under investigation. (ii) In the final measurements Hardy's proposal utilises a varying strengths of the local oscillator fields, whereas in the TWC case they are constant. In fact the local oscillators in Hardy's scheme are either on or off (the local setting is specified by the presence or absence of the local auxiliary field). We show that it is the varying strength of the local oscillators, from setting to setting, which is the crucial feature enabling violation of local realism in the Hardy setup, whereas it is not necessary to use initial superposition of a single photon excitation with vacuum as the initial state of the input mode. Neither one needs to operate in the fully on/off detection scheme. Despite the failure of the Tan, Walls and Collett scheme in proving Bell nonclassicality, we show that their scheme can serve as an entanglement indicator.},
     urldate = {2021-07-28},
     journal = {arXiv:2102.06689 [quant-ph]},
     month = feb,
     year = {2021},
     note = {arXiv: 2102.06689},
     keywords = {Quantum Physics},
   }

3. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, Bianka Woloncewicz, and Marek Żukowski. On detecting violation of local realism with photon-number resolving weak-field homodyne measurements. arXiv:2104.10703 [quant-ph], apr 2021. arXiv: 2104.10703
   [BibTeX] [Abstract] [Download PDF]
   

   Non-existence of a local hidden variables (LHV) model for a phenomenon benchmarks its use in device-independent quantum protocols. Nowadays photon-number resolving weak-field homodyne measurements allow realization of emblematic gedanken experiments. Alas, claims that we can have no LHV models for such experiments on (a) excitation of a pair of spatial modes by a single photon, and (b) two spatial modes in a weakly squeezed vacuum state, involving constant local oscillator strengths, are unfounded. For (a) an exact LHV model resolves the dispute on the “non-locality of a single photon” in its original formulation. It is measurements with local oscillators on or off that do not have LHV models.

   @article{das_detecting_2021,
     title = {On detecting violation of local realism with photon-number resolving weak-field homodyne measurements},
     url = {http://arxiv.org/abs/2104.10703},
     abstract = {Non-existence of a local hidden variables (LHV) model for a phenomenon benchmarks its use in device-independent quantum protocols. Nowadays photon-number resolving weak-field homodyne measurements allow realization of emblematic gedanken experiments. Alas, claims that we can have no LHV models for such experiments on (a) excitation of a pair of spatial modes by a single photon, and (b) two spatial modes in a weakly squeezed vacuum state, involving constant local oscillator strengths, are unfounded. For (a) an exact LHV model resolves the dispute on the "non-locality of a single photon" in its original formulation. It is measurements with local oscillators on or off that do not have LHV models.},
     urldate = {2021-07-28},
     journal = {arXiv:2104.10703 [quant-ph]},
     author = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Woloncewicz, Bianka and Żukowski, Marek},
     month = apr,
     year = {2021},
     note = {arXiv: 2104.10703},
     keywords = {Quantum Physics},
   }

4. Massimiliano Incudini, Fabio Tarocco, Riccardo Mengoni, Alessandra Di Pierro, and Antonio Mandarino. Benchmarking Small-Scale Quantum Devices on Computing Graph Edit Distance. arXiv e-prints, pages arXiv:2111.10183, nov 2021.
   [BibTeX] [Abstract] [Download PDF]
   

   Distance measures provide the foundation for many popular algorithms in Machine Learning and Pattern Recognition. Different notions of distance can be used depending on the types of the data the algorithm is working on. For graph-shaped data, an important notion is the Graph Edit Distance (GED) that measures the degree of (dis)similarity between two graphs in terms of the operations needed to make them identical. As the complexity of computing GED is the same as NP-hard problems, it is reasonable to consider approximate solutions. In this paper we present a comparative study of two quantum approaches to computing GED: quantum annealing and variational quantum algorithms, which refer to the two types of quantum hardware currently available, namely quantum annealer and gate-based quantum computer, respectively. Considering the current state of noisy intermediate-scale quantum computers, we base our study on proof-of-principle tests of the performance of these quantum algorithms.

   @Article{Incudini2021a,
     author        = {Incudini, Massimiliano and Tarocco, Fabio and Mengoni, Riccardo and Di Pierro, Alessandra and Mandarino, Antonio},
     journal       = {arXiv e-prints},
     title         = {Benchmarking {S}mall-{S}cale {Q}uantum {D}evices on {C}omputing {G}raph {E}dit {D}istance},
     year          = {2021},
     month         = nov,
     pages         = {arXiv:2111.10183},
     abstract      = {Distance measures provide the foundation for many popular algorithms in         Machine Learning and Pattern Recognition. Different notions of         distance can be used depending on the types of the data the         algorithm is working on. For graph-shaped data, an important         notion is the Graph Edit Distance (GED) that measures the degree         of (dis)similarity between two graphs in terms of the operations         needed to make them identical. As the complexity of computing         GED is the same as NP-hard problems, it is reasonable to         consider approximate solutions. In this paper we present a         comparative study of two quantum approaches to computing GED:         quantum annealing and variational quantum algorithms, which         refer to the two types of quantum hardware currently available,         namely quantum annealer and gate-based quantum computer,         respectively. Considering the current state of noisy         intermediate-scale quantum computers, we base our study on         proof-of-principle tests of the performance of these quantum         algorithms.},
     archiveprefix = {arXiv},
     eid           = {arXiv:2111.10183},
     eprint        = {2111.10183},
     keywords      = {Quantum Physics, Computer Science - Machine Learning},
     primaryclass  = {quant-ph},
     url           = {https://ui.adsabs.harvard.edu/abs/2021arXiv211110183I},
   }

5. 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},
   }

6. Marek Winczewski, Antonio Mandarino, Michał Horodecki, and Robert Alicki. Bypassing the Intermediate Times Dilemma for Open Quantum System. , 2021. doi:10.48550/ARXIV.2106.05776
   [BibTeX] [Download PDF]

   @article{arXiv_Bypasing_Dillema,
     doi = {10.48550/ARXIV.2106.05776},
     url = {https://arxiv.org/abs/2106.05776},
     author = {Winczewski, Marek and Mandarino, Antonio and Horodecki, Michał and Alicki, Robert},
     keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences},
     title = {Bypassing the Intermediate Times Dilemma for Open Quantum System},
     publisher = {arXiv},
     year = {2021},
     copyright = {Creative Commons Attribution 4.0 International}
   }

7. Tamoghna Das, Marcin Karczewski, Antonio Mandarino, Marcin Markiewicz, and Marek Żukowski. Optimal interferometry for Bell$-$nonclassicality by a vacuum$-$one$-$photon qubit. , 2021. doi:10.48550/ARXIV.2109.10170
   [BibTeX] [Download PDF]

   @article{https://doi.org/10.48550/arxiv.2109.10170,
     doi = {10.48550/ARXIV.2109.10170},
     url = {https://arxiv.org/abs/2109.10170},
     author = {Das, Tamoghna and Karczewski, Marcin and Mandarino, Antonio and Markiewicz, Marcin and Żukowski, Marek},
     keywords = {Quantum Physics (quant-ph), FOS: Physical sciences, FOS: Physical sciences},
     title = {Optimal interferometry for {Bell}$-$nonclassicality by a vacuum$-$one$-$photon qubit},
     publisher = {arXiv},
     year = {2021},
     
     copyright = {arXiv.org perpetual, non-exclusive license}
   }