{"topic":"quantum-foundations","sort":"top","limit":25,"offset":0,"count":25,"papers":[{"id":"arxiv:1508.05949","kind":"article","title":"Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres","authors":["Bas Hensen","Hannes Bernien","A. Dréau","Andreas Reiserer","Norbert Kalb","Machiel Blok","Justus W. Ruitenberg","R. F. L. Vermeulen","Raymond N. Schouten","Carlos Abellán","Waldimar Amaya","Valerio Pruneri","Morgan W. Mitchell","Matthew Markham","Daniel J. Twitchen","David Elkouss","Stephanie Wehner","T. H. Taminiau","Ronald Hanson"],"author_count":19,"year":2015,"published":"2015-10-01","venue":"Nature","cited_by":2846,"doi":"10.1038/nature15759","arxiv_id":"1508.05949","nct_id":null,"source_url":"https://doi.org/10.1038/nature15759","archive_url":"https://space-kitty.com/papers/arxiv:1508.05949","updated":"2015-08-24","pmid":"26503041","pmcid":null,"openalex_id":"W1709784975","pdf_url":"https://arxiv.org/pdf/1508.05949","abstract":"For more than 80 years, the counterintuitive predictions of quantum theory have stimulated debate about the nature of reality. In his seminal work, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Bell showed that in any local realist theory the correlations between distant measurements satisfy an inequality and, moreover, that this inequality can be violated according to quantum theory. This provided a recipe for experimental tests of the fundamental principles underlying the laws of nature. In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we report on a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell's inequality. We employ an event-ready scheme that enables the generation of high-fidelity entanglement between distant electron spins. Efficient spin readout avoids the fair sampling assumption (detection loophole), while the use of fast random basis selection and readout combined with a spatial separation of 1.3 km ensure the required locality conditions. We perform 245 trials testing the CHSH-Bell inequality $S \\leq 2$ and find $S = 2.42 \\pm 0.20$. A null hypothesis test yields a probability of $p = 0.039$ that a local-realist model for space-like separated sites produces data with a violation at least as large as observed, even when allowing for memory in the devices. This result rules out large classes of local realist theories, and paves the way for implementing device-independent quantum-secure communication and randomness certification.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by-nc-nd","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1511.03190","kind":"article","title":"Significant-Loophole-Free Test of Bell’s Theorem with Entangled Photons","authors":["Marissa Giustina","Marijn A. M. Versteegh","Sören Wengerowsky","Johannes Handsteiner","Armin Hochrainer","Kevin Phelan","Fabian Steinlechner","Johannes Kofler","Jan-Åke Larsson","Carlos Abellán","Waldimar Amaya","Valerio Pruneri","Morgan W. Mitchell","J. Beyer","Thomas Gerrits","Adriana E. Lita","Lynden K. Shalm","Sae Woo Nam","Thomas Scheidl","Rupert Ursin","Bernhard Wittmann","Anton Zeilinger"],"author_count":22,"year":2015,"published":"2015-12-16","venue":"Physical Review Letters","cited_by":1529,"doi":"10.1103/physrevlett.115.250401","arxiv_id":"1511.03190","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.115.250401","archive_url":"https://space-kitty.com/papers/arxiv:1511.03190","updated":"2015-12-20","pmid":"26722905","pmcid":null,"openalex_id":"W2174298480","pdf_url":"https://arxiv.org/pdf/1511.03190","abstract":"Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly supported the quantum predictions. Yet, every experiment requires assumptions that provide loopholes for a local realist explanation. Here we report a Bell test that closes the most significant of these loopholes simultaneously. Using a well-optimized source of entangled photons, rapid setting generation, and highly efficient superconducting detectors, we observe a violation of a Bell inequality with high statistical significance. The purely statistical probability of our results to occur under local realism does not exceed $3.74 \\times 10^{-31}$, corresponding to an 11.5 standard deviation effect.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1511.03189","kind":"article","title":"Strong Loophole-Free Test of Local Realism","authors":["Lynden K. Shalm","Evan Meyer-Scott","Bradley Christensen","Peter Bierhorst","Michael A. Wayne","Martin J. Stevens","Thomas Gerrits","Scott Glancy","Deny R. Hamel","Michael S. Allman","Kevin J. Coakley","Shellee D. Dyer","Carson Hodge","Adriana E. Lita","Varun B. Verma","Camilla Lambrocco","Edward Tortorici","Alan L. Migdall","Yanbao Zhang","Daniel R. Kumor","William H. Farr","Francesco Marsili","Matthew D. Shaw","Jeffrey A. Stern","Carlos Abellán"],"author_count":34,"year":2015,"published":"2015-12-16","venue":"Physical Review Letters","cited_by":1402,"doi":"10.1103/physrevlett.115.250402","arxiv_id":"1511.03189","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.115.250402","archive_url":"https://space-kitty.com/papers/arxiv:1511.03189","updated":"2016-09-06","pmid":"26722906","pmcid":null,"openalex_id":"W2762179548","pdf_url":"http://link.aps.org/pdf/10.1103/PhysRevLett.115.250402","abstract":"We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using a hypothesis test, we compute p-values as small as $5.9\\times 10^{-9}$ for our Bell violation while maintaining the spacelike separation of our events. We estimate the degree to which a local realistic system could predict our measurement choices. Accounting for this predictability, our smallest adjusted p-value is $2.3 \\times 10^{-7}$. We therefore reject the hypothesis that local realism governs our experiment.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1306.5772","kind":"article","title":"Detection-Loophole-Free Test of Quantum Nonlocality, and Applications","authors":["Bradley Christensen","Kevin T. McCusker","Joseph B. Altepeter","Brice Calkins","Thomas Gerrits","Adriana E. Lita","Aaron Miller","Lynden K. Shalm","Yu Zhang","Sae Woo Nam","Nicolas Brunner","Charles Ci Wen Lim","Nicolas Gisin","Paul G. Kwiat"],"author_count":14,"year":2013,"published":"2013-09-26","venue":"Physical Review Letters","cited_by":477,"doi":"10.1103/physrevlett.111.130406","arxiv_id":"1306.5772","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.111.130406","archive_url":"https://space-kitty.com/papers/arxiv:1306.5772","updated":"2013-09-26","pmid":"24116754","pmcid":null,"openalex_id":"W2006166792","pdf_url":"https://arxiv.org/pdf/1306.5772","abstract":"We present a source of entangled photons that violates a Bell inequality free of the \"fair-sampling\" assumption, by over 7 standard deviations. This violation is the first experiment with photons to close the detection loophole, and we demonstrate enough \"efficiency\" overhead to eventually perform a fully loophole-free test of local realism. The entanglement quality is verified by maximally violating additional Bell tests, testing the upper limit of quantum correlations. Finally, we use the source to generate secure private quantum random numbers at rates over 4 orders of magnitude beyond previous experiments.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"other-oa","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"doi:10.1038/s41586-023-05885-0","kind":"article","title":"Loophole-free Bell inequality violation with superconducting circuits","authors":["Simon Storz","Josua Schär","Anatoly Kulikov","Paul Magnard","Philipp Kurpiers","Janis Lütolf","T. Walter","Adrian Copetudo","Kevin Reuer","Abdulkadir Akın","Jean-Claude Besse","Mihai S. Gabureac","Graham J. Norris","Andrés Rosario Hamann","Ferran Martin Ciurana","José Martinez","Waldimar Amaya","Morgan W. Mitchell","Carlos Abellán","Jean-Daniel Bancal","Nicolas Sangouard","Baptiste Royer","Alexandre Blais","Andreas J. Wallraff"],"author_count":24,"year":2023,"published":"2023-05-10","venue":"Nature","cited_by":219,"doi":"10.1038/s41586-023-05885-0","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.1038/s41586-023-05885-0","archive_url":"https://space-kitty.com/papers/doi:10.1038/s41586-023-05885-0","updated":null,"pmid":"37165240","pmcid":null,"openalex_id":"W4376130945","pdf_url":"https://www.nature.com/articles/s41586-023-05885-0.pdf","abstract":"Abstract Superposition, entanglement and non-locality constitute fundamental features of quantum physics. The fact that quantum physics does not follow the principle of local causality1–3 can be experimentally demonstrated in Bell tests4 performed on pairs of spatially separated, entangled quantum systems. Although Bell tests, which are widely regarded as a litmus test of quantum physics, have been explored using a broad range of quantum systems over the past 50 years, only relatively recently have experiments free of so-called loopholes5 succeeded. Such experiments have been performed with spins in nitrogen–vacancy centres6, optical photons7–9 and neutral atoms10. Here we demonstrate a loophole-free violation of Bell’s inequality with superconducting circuits, which are a prime contender for realizing quantum computing technology11. To evaluate a Clauser–Horne–Shimony–Holt-type Bell inequality4, we deterministically entangle a pair of qubits12 and perform fast and high-fidelity measurements13 along randomly chosen bases on the qubits connected through a cryogenic link14 spanning a distance of 30 metres. Evaluating more than 1 million experimental trials, we find an average S value of 2.0747 ± 0.0033, violating Bell’s inequality with a P value smaller than 10−108. Our work demonstrates that non-locality is a viable new resource in quantum information technology realized with superconducting circuits with potential applications in quantum communication, quantum computing and fundamental physics15.","abstract_license":"CC-BY (publisher license, via OpenAlex)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex","attribution":"Abstract of \"Loophole-free Bell inequality violation with superconducting circuits\" by Simon Storz, Josua Schär, Anatoly Kulikov et al., https://doi.org/10.1038/s41586-023-05885-0, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified."},{"id":"doi:10.1038/s41467-017-02307-4","kind":"article","title":"Practical device-independent quantum cryptography via entropy accumulation","authors":["Rotem Arnon-Friedman","Frédéric Dupuis","Omar Fawzi","Renato Renner","Thomas Vidick"],"author_count":5,"year":2018,"published":"2018-01-25","venue":"Nature Communications","cited_by":271,"doi":"10.1038/s41467-017-02307-4","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.1038/s41467-017-02307-4","archive_url":"https://space-kitty.com/papers/doi:10.1038/s41467-017-02307-4","updated":null,"pmid":"29386507","pmcid":null,"openalex_id":"W2785593271","pdf_url":"https://www.nature.com/articles/s41467-017-02307-4.pdf","abstract":"Device-independent cryptography goes beyond conventional quantum cryptography by providing security that holds independently of the quality of the underlying physical devices. Device-independent protocols are based on the quantum phenomena of non-locality and the violation of Bell inequalities. This high level of security could so far only be established under conditions which are not achievable experimentally. Here we present a property of entropy, termed \"entropy accumulation\", which asserts that the total amount of entropy of a large system is the sum of its parts. We use this property to prove the security of cryptographic protocols, including device-independent quantum key distribution, while achieving essentially optimal parameters. Recent experimental progress, which enabled loophole-free Bell tests, suggests that the achieved parameters are technologically accessible. Our work hence provides the theoretical groundwork for experimental demonstrations of device-independent cryptography.","abstract_license":"CC-BY (publisher license, via OpenAlex)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex","attribution":"Abstract of \"Practical device-independent quantum cryptography via entropy accumulation\" by Rotem Arnon-Friedman, Frédéric Dupuis, Omar Fawzi et al., https://doi.org/10.1038/s41467-017-02307-4, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified."},{"id":"arxiv:1807.09611","kind":"article","title":"Device-independent quantum random-number generation","authors":["Yang Liu","Qi Zhao","Minghan Li","Jian-Yu Guan","Yanbao Zhang","Bing Bai","Weijun Zhang","Wen‐Zhao Liu","Cheng Wu","Xiao Yuan","Hao Li","William J. Munro","Zhen Wang","Lixing You","Jun Zhang","Xiongfeng Ma","Jingyun Fan","Qiang Zhang","Jian-Wei Pan"],"author_count":19,"year":2018,"published":"2018-09-13","venue":"Nature","cited_by":258,"doi":"10.1038/s41586-018-0559-3","arxiv_id":"1807.09611","nct_id":null,"source_url":"https://doi.org/10.1038/s41586-018-0559-3","archive_url":"https://space-kitty.com/papers/arxiv:1807.09611","updated":"2018-07-27","pmid":"30287887","pmcid":null,"openalex_id":"W2231272853","pdf_url":"https://arxiv.org/pdf/1807.09611","abstract":"Randomness is critical for many information processing applications, including numerical modeling and cryptography. Device-independent quantum random number generation (DIQRNG) based on the loophole free violation of Bell inequality produces unpredictable genuine randomness without any device assumption and is therefore an ultimate goal in the field of quantum information science. However, due to formidable technical challenges, there were very few reported experimental studies of DIQRNG, which were vulnerable to the adversaries. Here we present a fully functional DIQRNG against the most general quantum adversaries. We construct a robust experimental platform that realizes Bell inequality violation with entangled photons with detection and locality loopholes closed simultaneously. This platform enables a continuous recording of a large volume of data sufficient for security analysis against the general quantum side information and without assuming independent and identical distribution. Lastly, by developing a large Toeplitz matrix (137.90 Gb $\\times$ 62.469 Mb) hashing technique, we demonstrate that this DIQRNG generates $6.2469\\times 10^7$ quantum-certified random bits in 96 hours (or 181 bits/s) with uniformity within $10^{-5}$. We anticipate this DIQRNG may have profound impact on the research of quantum randomness and information-secured applications.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1407.0363","kind":"article","title":"Loopholes in Bell inequality tests of local realism","authors":["Jan-Åke Larsson"],"author_count":1,"year":2014,"published":"2014-10-09","venue":"Journal of Physics A Mathematical and Theoretical","cited_by":261,"doi":"10.1088/1751-8113/47/42/424003","arxiv_id":"1407.0363","nct_id":null,"source_url":"https://doi.org/10.1088/1751-8113/47/42/424003","archive_url":"https://space-kitty.com/papers/arxiv:1407.0363","updated":"2014-07-01","pmid":null,"pmcid":null,"openalex_id":"W1990727816","pdf_url":"https://iopscience.iop.org/article/10.1088/1751-8113/47/42/424003/pdf","abstract":"Bell inequalities are intended to show that local realist theories cannot describe the world. A local realist theory is one where physical properties are defined prior to and independent of measurement, and no physical influence can propagate faster than the speed of light. Quantum-mechanical predictions for certain experiments violate the Bell inequality while a local realist theory cannot, and this shows that a local realist theory cannot give those quantum-mechanical predictions. However, because of unexpected circumstances or \"loopholes\" in available experiment tests, local realist theories can reproduce the data from these experiments. This paper reviews such loopholes, what effect they have on Bell inequality tests, and how to avoid them in experiment. Avoiding all these simultaneously in one experiment, usually called a \"loophole-free\" or \"definitive\" Bell test, remains an open task, but is very important for technological tasks such as device-independent security of quantum cryptography, and ultimately for our understanding of the world.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1111.0829","kind":"article","title":"Conclusive quantum steering with superconducting transition-edge sensors","authors":["Devin H. Smith","Geoff Gillett","Marcelo Pereira de Almeida","Cyril Branciard","Alessandro Fedrizzi","Till J. Weinhold","Adriana E. Lita","Brice Calkins","Thomas Gerrits","Howard M. Wiseman","Sae Woo Nam","Andrew G. White"],"author_count":12,"year":2012,"published":"2012-01-10","venue":"Nature Communications","cited_by":237,"doi":"10.1038/ncomms1628","arxiv_id":"1111.0829","nct_id":null,"source_url":"https://doi.org/10.1038/ncomms1628","archive_url":"https://space-kitty.com/papers/arxiv:1111.0829","updated":"2012-01-11","pmid":"22233635","pmcid":null,"openalex_id":"W2121437177","pdf_url":"https://www.nature.com/articles/ncomms1628.pdf","abstract":"Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date all experimental tests with single photon states have relied on post-selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this \"detection loophole\" by combining a highly efficient source of entangled photon pairs with superconducting transition edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 standard deviations. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by-nc-sa","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2110.01480","kind":"article","title":"Toward a Photonic Demonstration of Device-Independent Quantum Key Distribution","authors":["Wen‐Zhao Liu","Yuzhe Zhang","Yi-Zheng Zhen","Ming-Han Li","Yang Liu","Jingyun Fan","Feihu Xu","Qiang Zhang","Jian-Wei Pan"],"author_count":9,"year":2022,"published":"2022-07-27","venue":"Physical Review Letters","cited_by":134,"doi":"10.1103/physrevlett.129.050502","arxiv_id":"2110.01480","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.129.050502","archive_url":"https://space-kitty.com/papers/arxiv:2110.01480","updated":"2022-03-21","pmid":"35960585","pmcid":null,"openalex_id":"W4288051251","pdf_url":"https://arxiv.org/pdf/2110.01480","abstract":"In this paper, we employ theoretical and experimental efforts and realize a proof-of-principle verification of device-independent QKD based on the photonic setup. On the theoretical side, we enhance the loss tolerance for real device imperfections by combining different approaches, namely, random post-selection, noisy preprocessing, and developed numerical methods to estimate the key rate via the von Neumann entropy. On the experimental side, we develop a high-quality polarization-entangled photon source achieving a state-of-the-art (heralded) detection efficiency about 87.5%. This efficiency outperforms previous photonic experiments involving loophole-free Bell tests. Together, we show that the measured quantum correlations are strong enough to ensure a positive key rate under the fiber length up to 220 m. Our photonic platform can generate entangled photons at a high rate and in the telecom wavelength, which is desirable for high-speed generation over long distances. The results present an important step towards a full demonstration of photonic device-independent QKD.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"doi:10.1103/physreva.84.062101","kind":"article","title":"Tomography of the quantum state of photons entangled in high dimensions","authors":["Megan Agnew","Jonathan Leach","Melanie G. McLaren","F. Stef Roux","Robert W. Boyd"],"author_count":5,"year":2011,"published":"2011-12-02","venue":"Physical Review A","cited_by":162,"doi":"10.1103/physreva.84.062101","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.1103/physreva.84.062101","archive_url":"https://space-kitty.com/papers/doi:10.1103/physreva.84.062101","updated":null,"pmid":null,"pmcid":null,"openalex_id":"W2123448231","pdf_url":null,"abstract":null,"abstract_license":null,"license":null,"is_open_access":false,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex","attribution":"Metadata and citation counts: OpenAlex (CC0)."},{"id":"arxiv:1709.06779","kind":"article","title":"High-Speed Device-Independent Quantum Random Number Generation without a Detection Loophole","authors":["Yang Liu","Xiao Yuan","Minghan Li","Weijun Zhang","Qi Zhao","Jiaqiang Zhong","Yuan Wen Cao","Yu-Huai Li","Luo-Kan Chen","Hao Li","Tianyi Peng","Yu-Ao Chen","Cheng-Zhi Peng","Sheng‐Cai Shi","Zhen Wang","Lixing You","Xiongfeng Ma","Jingyun Fan","Qiang Zhang","Jian-Wei Pan"],"author_count":20,"year":2018,"published":"2018-01-03","venue":"Physical Review Letters","cited_by":140,"doi":"10.1103/physrevlett.120.010503","arxiv_id":"1709.06779","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.120.010503","archive_url":"https://space-kitty.com/papers/arxiv:1709.06779","updated":"2017-09-20","pmid":"29350962","pmcid":null,"openalex_id":"W2754819841","pdf_url":"https://arxiv.org/pdf/1709.06779","abstract":"Quantum mechanics provides means of generating genuine randomness that is impossible with deterministic classical processes. Remarkably, the unpredictability of randomness can be certified in a self-testing manner that is independent of implementation devices. Here, we present an experimental demonstration of self-testing quantum random number generation based on an detection-loophole free Bell test with entangled photons. In the randomness analysis, without the assumption of independent identical distribution, we consider the worst case scenario that the adversary launches the most powerful attacks against quantum adversary. After considering statistical fluctuations and applying an 80 Gb $\\times$ 45.6 Mb Toeplitz matrix hashing, we achieve a final random bit rate of 114 bits/s, with a failure probability less than $10^{-5}$. Such self-testing random number generators mark a critical step towards realistic applications in cryptography and fundamental physics tests.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1103.4949","kind":"article","title":"Violation of a Temporal Bell Inequality for Single Spins in a Diamond Defect Center","authors":["G. Waldherr","Philipp Neumann","Susana F. Huelga","Fedor Jelezko","Jörg Wrachtrup"],"author_count":5,"year":2011,"published":"2011-08-24","venue":"Physical Review Letters","cited_by":145,"doi":"10.1103/physrevlett.107.090401","arxiv_id":"1103.4949","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.107.090401","archive_url":"https://space-kitty.com/papers/arxiv:1103.4949","updated":"2011-03-25","pmid":"21929214","pmcid":null,"openalex_id":"W187172663","pdf_url":"https://arxiv.org/pdf/1103.4949","abstract":"Quantum non-locality has been experimentally investigated by testing different forms of Bell's inequality, yet a loophole-free realization has not been achieved up to now. Much less explored are temporal Bell inequalities, which are not subject to the locality assumption, but impose a constrain on the system's time-correlations. In this paper, we report on the experimental violation of a temporal Bell's inequality using a nitrogen vacancy defect (NV) in diamond and provide a novel quantitative test of quantum coherence. We therefore present a new technique to initialize the electronic state of the NV with high fidelity, a necessary requirement for reliable quantum information processing and/or the implementation of protocols for quantum metrology.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Diamond and Carbon-based Materials Research"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1506.02712","kind":"article","title":"Generation of Fresh and Pure Random Numbers for Loophole-Free Bell Tests","authors":["Carlos Abellán","Waldimar Amaya","Daniel Mitrani","Valerio Pruneri","Morgan W. Mitchell"],"author_count":5,"year":2015,"published":"2015-12-16","venue":"Physical Review Letters","cited_by":116,"doi":"10.1103/physrevlett.115.250403","arxiv_id":"1506.02712","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.115.250403","archive_url":"https://space-kitty.com/papers/arxiv:1506.02712","updated":"2015-12-17","pmid":"26722907","pmcid":null,"openalex_id":"W1174099912","pdf_url":"https://arxiv.org/pdf/1506.02712","abstract":"We demonstrate extraction of randomness from spontaneous-emission events less than 36 ns in the past, giving output bits with excess predictability below $10^{-5}$ and strong metrological randomness assurances. This randomness generation strategy satisfies the stringent requirements for unpredictable basis choices in current \"loophole-free Bell tests\" of local realism [Hensen et al., Nature (London) 526, 682 (2015); Giustina et al., Phys. Rev. Lett. 115, 250401 (2015); Shalm et al., Phys. Rev. Lett. 115, 250402 (2015)].","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1603.05705","kind":"article","title":"Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis","authors":["Bas Hensen","Norbert Kalb","Machiel Blok","A. Dréau","Andreas Reiserer","R. F. L. Vermeulen","Raymond N. Schouten","Matthew Markham","Daniel J. Twitchen","Kenneth Goodenough","David Elkouss","Stephanie Wehner","T. H. Taminiau","Ronald Hanson"],"author_count":14,"year":2016,"published":"2016-08-11","venue":"Scientific Reports","cited_by":95,"doi":"10.1038/srep30289","arxiv_id":"1603.05705","nct_id":null,"source_url":"https://doi.org/10.1038/srep30289","archive_url":"https://space-kitty.com/papers/arxiv:1603.05705","updated":"2016-04-01","pmid":"27509823","pmcid":null,"openalex_id":"W2298740677","pdf_url":"https://www.nature.com/articles/srep30289.pdf","abstract":"The recently reported violation of a Bell inequality using entangled electronic spins in diamonds (Hensen et al., Nature 526, 682-686) provided the first loophole-free evidence against local-realist theories of nature. Here we report on data from a second Bell experiment using the same experimental setup with minor modifications. We find a violation of the CHSH-Bell inequality of $2.35 \\pm 0.18$, in agreement with the first run, yielding an overall value of $S = 2.38 \\pm 0.14$. We calculate the resulting $P$-values of the second experiment and of the combined Bell tests. We provide an additional analysis of the distribution of settings choices recorded during the two tests, finding that the observed distributions are consistent with uniform settings for both tests. Finally, we analytically study the effect of particular models of random number generator (RNG) imperfection on our hypothesis test. We find that the winning probability per trial in the CHSH game can be bounded knowing only the mean of the RNG bias, implying that our experimental result is robust for any model underlying the estimated average RNG bias.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1603.08254","kind":"article","title":"Nonlocality from local contextuality","authors":["Bi-Heng Liu","Xiao-Min Hu","Jiang-Shan Chen","Yun-Feng Huang","Yong-Jian Han","Chuan-Feng Li","Guang-Can Guo","Adán Cabello"],"author_count":8,"year":2016,"published":"2016-03-27","venue":"Phys. Rev. Lett. 117, 220402 (2016)","cited_by":40,"doi":"10.1103/physrevlett.117.220402","arxiv_id":"1603.08254","nct_id":null,"source_url":"https://arxiv.org/abs/1603.08254","archive_url":"https://space-kitty.com/papers/arxiv:1603.08254","updated":"2016-11-23","pmid":null,"pmcid":null,"openalex_id":"W2554397123","pdf_url":"https://arxiv.org/pdf/1603.08254","abstract":"We experimentally show that nonlocality can be produced from single-particle contextuality by using two-particle correlations which do not violate any Bell inequality by themselves. This demonstrates that nonlocality can come from an {\\em a priori} different simpler phenomenon, and connects contextuality and nonlocality, the two critical resources for, respectively, quantum computation and secure communication. From the perspective of quantum information, our experiment constitutes a proof of principle that quantum systems can be used simultaneously for both quantum computation and secure communication.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"peer_reviewed":null,"categories":["quant-ph"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1411.4787","kind":"article","title":"Requirements for a loophole-free photonic Bell test using imperfect setting generators","authors":["Johannes Kofler","Marissa Giustina","Jan-Åke Larsson","Morgan W. Mitchell"],"author_count":4,"year":2016,"published":"2016-03-10","venue":"Physical Review A","cited_by":87,"doi":"10.1103/physreva.93.032115","arxiv_id":"1411.4787","nct_id":null,"source_url":"https://doi.org/10.1103/physreva.93.032115","archive_url":"https://space-kitty.com/papers/arxiv:1411.4787","updated":"2016-03-10","pmid":null,"pmcid":null,"openalex_id":"W2295481020","pdf_url":"http://link.aps.org/pdf/10.1103/PhysRevA.93.032115","abstract":"Experimental violations of Bell inequalities are in general vulnerable to so-called \"loopholes.\" In this work, we analyse the characteristics of a loophole-free Bell test with photons, closing simultaneously the locality, freedom-of-choice, fair-sampling (i.e. detection), coincidence-time, and memory loopholes. We pay special attention to the effect of excess predictability in the setting choices due to non-ideal random number generators. We discuss necessary adaptations of the CH/Eberhard inequality when using such imperfect devices and -- using Hoeffding's inequality and Doob's optional stopping theorem -- the statistical analysis in such Bell tests.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1804.10150","kind":"article","title":"Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement","authors":["Francesco Vedovato","Costantino Agnesi","Marco Tomasin","Marco Avesani","Jan-Åke Larsson","Giuseppe Vallone","Paolo Villoresi"],"author_count":7,"year":2018,"published":"2018-11-09","venue":"Physical Review Letters","cited_by":68,"doi":"10.1103/physrevlett.121.190401","arxiv_id":"1804.10150","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.121.190401","archive_url":"https://space-kitty.com/papers/arxiv:1804.10150","updated":"2018-11-09","pmid":"30468593","pmcid":null,"openalex_id":"W2798934590","pdf_url":"http://link.aps.org/pdf/10.1103/PhysRevLett.121.190401","abstract":"Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free-space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bell's inequality with \"genuine\" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed to obtain a postselection-loophole-free Bell violation of more than nine standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modern integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1911.09696","kind":"article","title":"Generalized probability rules from a timeless formulation of Wigner's friend scenarios","authors":["Veronika Baumann","Flavio Del Santo","Alexander R. H. Smith","Flaminia Giacomini","Esteban Castro-Ruiz","Caslav Brukner"],"author_count":6,"year":2019,"published":"2019-11-21","venue":"Quantum 5, 524 (2021)","cited_by":40,"doi":"10.22331/q-2021-08-16-524","arxiv_id":"1911.09696","nct_id":null,"source_url":"https://arxiv.org/abs/1911.09696","archive_url":"https://space-kitty.com/papers/arxiv:1911.09696","updated":"2021-08-11","pmid":null,"pmcid":null,"openalex_id":"W2989720944","pdf_url":"https://arxiv.org/pdf/1911.09696","abstract":"The quantum measurement problem can be regarded as the tension between the two alternative dynamics prescribed by quantum mechanics: the unitary evolution of the wave function and the state-update rule (or \"collapse\") at the instant a measurement takes place. The notorious Wigner's friend gedankenexperiment constitutes the paradoxical scenario in which different observers (one of whom is observed by the other) describe one and the same interaction differently, one --the Friend-- via state-update and the other --Wigner-- unitarily. This can lead to Wigner and his friend assigning different probabilities to the outcome of the same subsequent measurement. In this paper, we apply the Page-Wootters mechanism (PWM) as a timeless description of Wigner's friend-like scenarios. We show that the standard rules to assign two-time conditional probabilities within the PWM need to be modified to deal with the Wigner's friend gedankenexperiment. We identify three main definitions of such modified rules to assign two-time conditional probabilities, all of which reduce to standard quantum theory for non-Wigner's friend scenarios. However, when applied to the Wigner's friend setup each rule assigns different conditional probabilities, potentially resolving the probability-assignment paradox in a different manner. Moreover, one rule imposes strict limits on when a joint probability distribution for the measurement outcomes of Wigner and his Friend is well-defined, which single out those cases where Wigner's measurement does not disturb the Friend's memory and such a probability has an operational meaning in terms of collectible statistics. Interestingly, the same limits guarantee that said measurement outcomes fulfill the consistency condition of the consistent histories framework.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"peer_reviewed":null,"categories":["quant-ph"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1812.07786","kind":"article","title":"Experimental Low-Latency Device-Independent Quantum Randomness","authors":["Yanbao Zhang","Lynden K. Shalm","Joshua C. Bienfang","Martin J. Stevens","Michael D. Mazurek","Sae Woo Nam","Carlos Abellán","Waldimar Amaya","Morgan W. Mitchell","Honghao Fu","Carl A. Miller","Alan Mink","Emanuel H. Knill"],"author_count":13,"year":2020,"published":"2020-01-07","venue":"Physical Review Letters","cited_by":63,"doi":"10.1103/physrevlett.124.010505","arxiv_id":"1812.07786","nct_id":null,"source_url":"https://doi.org/10.1103/physrevlett.124.010505","archive_url":"https://space-kitty.com/papers/arxiv:1812.07786","updated":"2019-12-24","pmid":"31976704","pmcid":null,"openalex_id":"W2904773253","pdf_url":"https://arxiv.org/pdf/1812.07786","abstract":"Applications of randomness such as private key generation and public randomness beacons require small blocks of certified random bits on demand. Device-independent quantum random number generators can produce such random bits, but existing quantum-proof protocols and loophole-free implementations suffer from high latency, requiring many hours to produce any random bits. We demonstrate device-independent quantum randomness generation from a loophole-free Bell test with a more efficient quantum-proof protocol, obtaining multiple blocks of $512$ bits with an average experiment time of less than $5$ min per block and with a certified error bounded by $2^{-64}\\approx 5.42\\times 10^{-20}$.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"doi:10.1088/1402-4896/aa736d","kind":"article","title":"Light for the quantum. Entangled photons and their applications: a very personal perspective","authors":["Anton Zeilinger"],"author_count":1,"year":2017,"published":"2017-06-15","venue":"Physica Scripta","cited_by":67,"doi":"10.1088/1402-4896/aa736d","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.1088/1402-4896/aa736d","archive_url":"https://space-kitty.com/papers/doi:10.1088/1402-4896/aa736d","updated":null,"pmid":null,"pmcid":null,"openalex_id":"W2625021710","pdf_url":null,"abstract":"The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single- and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that nature cannot be local, that objective randomness exists and about the emergence of a classical world. It is suggestive that information plays a fundamental role also in the foundations of quantum physics.","abstract_license":"CC-BY (publisher license, via OpenAlex)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex","attribution":"Abstract of \"Light for the quantum. Entangled photons and their applications: a very personal perspective\" by Anton Zeilinger, https://doi.org/10.1088/1402-4896/aa736d, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified."},{"id":"arxiv:2011.13790","kind":"article","title":"Converting contextuality into nonlocality","authors":["Adán Cabello"],"author_count":1,"year":2020,"published":"2020-11-27","venue":"Phys. Rev. Lett. 127, 070401 (2021)","cited_by":41,"doi":"10.1103/physrevlett.127.070401","arxiv_id":"2011.13790","nct_id":null,"source_url":"https://arxiv.org/abs/2011.13790","archive_url":"https://space-kitty.com/papers/arxiv:2011.13790","updated":"2021-08-11","pmid":null,"pmcid":null,"openalex_id":"W3191774313","pdf_url":"https://arxiv.org/pdf/2011.13790","abstract":"We introduce a general method which converts, in a unified way, any form of quantum contextuality, including any form of state-dependent contextuality, into a quantum violation of a bipartite Bell inequality. As an example, we apply the method to a quantum violation of the Klyachko-Can-Binicioğlu-Shumovsky inequality.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"peer_reviewed":null,"categories":["quant-ph"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1312.2999","kind":"article","title":"A robust mathematical model for a loophole-free Clauser–Horne experiment","authors":["Peter Bierhorst"],"author_count":1,"year":2015,"published":"2015-04-17","venue":"Journal of Physics A Mathematical and Theoretical","cited_by":67,"doi":"10.1088/1751-8113/48/19/195302","arxiv_id":"1312.2999","nct_id":null,"source_url":"https://doi.org/10.1088/1751-8113/48/19/195302","archive_url":"https://space-kitty.com/papers/arxiv:1312.2999","updated":"2015-03-27","pmid":null,"pmcid":null,"openalex_id":"W3102592148","pdf_url":"https://arxiv.org/pdf/1312.2999","abstract":"Recent experiments have reached detection efficiencies sufficient to close the detection loophole, testing the Clauser-Horne (CH) version of Bell's inequality. For a similar future experiment to be completely loophole-free, it will be important to have discrete experimental trials with randomized measurement settings for each trial, and the statistical analysis should not overlook the possibility of a local state varying over time with possible dependence on earlier trials (the \"memory loophole\"). In this paper, a mathematical model for such a CH experiment is presented, and a method for statistical analysis that is robust to memory effects is introduced. Additionally, a new method for calculating exact p-values for martingale-based statistics is described; previously, only non-sharp upper bounds derived from the Azuma-Hoeffding inequality have been available for such statistics. This improvement decreases the required number of experimental trials to demonstrate non-locality. The statistical techniques are applied to the data of recent experiments and found to perform well.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"peer_reviewed":null,"categories":["Quantum Mechanics and Applications"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1907.05607","kind":"article","title":"A strong no-go theorem on the Wigner's friend paradox","authors":["Kok-Wei Bong","Aníbal Utreras-Alarcón","Farzad Ghafari","Yeong-Cherng Liang","Nora Tischler","Eric G. Cavalcanti","Geoff J. Pryde","Howard M. Wiseman"],"author_count":8,"year":2019,"published":"2019-07-12","venue":"Nat. Phys. 16, 1199-1205 (2020)","cited_by":224,"doi":"10.1038/s41567-020-0990-x","arxiv_id":"1907.05607","nct_id":null,"source_url":"https://arxiv.org/abs/1907.05607","archive_url":"https://space-kitty.com/papers/arxiv:1907.05607","updated":"2023-03-15","pmid":null,"pmcid":null,"openalex_id":"W3104348698","pdf_url":"https://arxiv.org/pdf/1907.05607","abstract":"Does quantum theory apply at all scales, including that of observers? New light on this fundamental question has recently been shed through a resurgence of interest in the long-standing Wigner's friend paradox. This is a thought experiment addressing the quantum measurement problem -- the difficulty of reconciling the (unitary, deterministic) evolution of isolated systems and the (non-unitary, probabilistic) state update after a measurement. Here, by building on a scenario with two separated but entangled friends introduced by Brukner, we prove that if quantum evolution is controllable on the scale of an observer, then one of 'No-Superdeterminism', 'Locality' or 'Absoluteness of Observed Events' -- that every observed event exists absolutely, not relatively -- must be false. We show that although the violation of Bell-type inequalities in such scenarios is not in general sufficient to demonstrate the contradiction between those three assumptions, new inequalities can be derived in a theory-independent manner, that are violated by quantum correlations. This is demonstrated in a proof-of-principle experiment where a photon's path is deemed an observer. We discuss how this new theorem places strictly stronger constraints on physical reality than Bell's theorem.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"peer_reviewed":null,"categories":["quant-ph"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"doi:10.1103/physrevresearch.2.013016","kind":"article","title":"Efficient randomness certification by quantum probability estimation","authors":["Yanbao Zhang","Honghao Fu","Emanuel H. Knill"],"author_count":3,"year":2020,"published":"2020-01-07","venue":"Physical Review Research","cited_by":47,"doi":"10.1103/physrevresearch.2.013016","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.1103/physrevresearch.2.013016","archive_url":"https://space-kitty.com/papers/doi:10.1103/physrevresearch.2.013016","updated":null,"pmid":"33313520","pmcid":null,"openalex_id":"W2999265232","pdf_url":"http://link.aps.org/pdf/10.1103/PhysRevResearch.2.013016","abstract":"For practical applications of quantum randomness generation, it is important to certify and further produce a fixed block of fresh random bits with as few trials as possible.Consequently, protocols with high finite-data efficiency are preferred.To yield such protocols with respect to quantum side information, we develop quantum probability estimation.Our approach is applicable to device-independent as well as device-dependent scenarios, and it generalizes techniques from previous works [Miller and Shi, SIAM J. Comput. 46, 1304 (2017); Arnon-Friedman et al., Nat. Commun. 9, 459 (2018)].Quantum probability estimation can adapt to changing experimental conditions, allows stopping the experiment as soon as the prespecified randomness goal is achieved, and can tolerate imperfect knowledge of the input distribution.Moreover, the randomness rate achieved at constant error is asymptotically optimal.For the device-independent scenario, our approach certifies the amount of randomness available in experimental results without first searching for relations between randomness and violations of fixed Bell inequalities.We implement quantum probability estimation for device-independent randomness generation in the CHSH Bell-test configuration, and we show significant improvements in finite-data efficiency, particularly at small Bell violations which are typical in current photonic loophole-free Bell tests.","abstract_license":"CC-BY (publisher license, via OpenAlex)","license":"cc-by","is_open_access":true,"peer_reviewed":null,"categories":["Quantum Information and Cryptography"],"details":null,"provenance":"openalex","attribution":"Abstract of \"Efficient randomness certification by quantum probability estimation\" by Yanbao Zhang, Honghao Fu, Emanuel H. Knill, https://doi.org/10.1103/physrevresearch.2.013016, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified."}],"next":"https://space-kitty.com/api/v1/topics/quantum-foundations/papers?sort=top&limit=25&offset=25"}