The Experts below are selected from a list of 8697 Experts worldwide ranked by ideXlab platform
Nicolas Gisin - One of the best experts on this subject based on the ideXlab platform.
-
demonstrating the power of Quantum computers certification of highly entangled measurements and scalable Quantum Nonlocality
npj Quantum Information, 2021Co-Authors: Nicolas Gisin, Elisa Baumer, Armin TavakoliAbstract:Increasingly sophisticated Quantum computers motivate the exploration of their abilities in certifying genuine Quantum phenomena. Here, we demonstrate the power of state-of-the-art IBM Quantum computers in correlation experiments inspired by Quantum networks. Our experiments feature up to 12 qubits and require the implementation of paradigmatic Bell-State Measurements for scalable entanglement-swapping. First, we demonstrate Quantum correlations that defy classical models in up to nine-qubit systems while only assuming that the Quantum computer operates on qubits. Harvesting these Quantum advantages, we are able to certify 82 basis elements as entangled in a 512-outcome measurement. Then, we relax the qubit assumption and consider Quantum Nonlocality in a scenario with multiple independent entangled states arranged in a star configuration. We report Quantum violations of source-independent Bell inequalities for up to ten qubits. Our results demonstrate the ability of Quantum computers to outperform classical limitations and certify scalable entangled measurements.
-
a neural network oracle for Quantum Nonlocality problems in networks
npj Quantum Information, 2020Co-Authors: Tamas Krivachy, Nicolas Gisin, Daniel Cavalcanti, Yu Cai, Arash Tavakoli, Nicolas BrunnerAbstract:Characterizing Quantum Nonlocality in networks is a challenging, but important problem. Using Quantum sources one can achieve distributions which are unattainable classically. A key point in investigations is to decide whether an observed probability distribution can be reproduced using only classical resources. This causal inference task is challenging even for simple networks, both analytically and using standard numerical techniques. We propose to use neural networks as numerical tools to overcome these challenges, by learning the classical strategies required to reproduce a distribution. As such, a neural network acts as an oracle for an observed behavior, demonstrating that it is classical if it can be learned. We apply our method to several examples in the triangle configuration. After demonstrating that the method is consistent with previously known results, we give solid evidence that a Quantum distribution recently proposed by Gisin is indeed nonlocal as conjectured. Finally we examine the genuinely nonlocal distribution recently presented by Renou et al., and, guided by the findings of the neural network, conjecture Nonlocality in a new range of parameters in these distributions. The method allows us to get an estimate on the noise robustness of all examined distributions.
-
genuine Quantum Nonlocality in the triangle network
Physical Review Letters, 2019Co-Authors: Marcolivier Renou, Nicolas Gisin, Nicolas Brunner, Elisa Baumer, Sadra Boreiri, Salman BeigiAbstract:Quantum networks allow in principle for completely novel forms of Quantum correlations. In particular, Quantum Nonlocality can be demonstrated here without the need of having various input settings, but only by considering the joint statistics of fixed local measurement outputs. However, previous examples of this intriguing phenomenon all appear to stem directly from the usual form of Quantum Nonlocality, namely via the violation of a standard Bell inequality. Here we present novel examples of "Quantum Nonlocality without inputs," which we believe represent a new form of Quantum Nonlocality, genuine to networks. Our simplest examples, for the triangle network, involve both entangled states and joint entangled measurements. A generalization to any odd-cycle network is also presented.
-
a neural network oracle for Quantum Nonlocality problems in networks
arXiv: Quantum Physics, 2019Co-Authors: Tamas Krivachy, Nicolas Gisin, Daniel Cavalcanti, Yu Cai, Arash Tavakoli, Nicolas BrunnerAbstract:Characterizing Quantum Nonlocality in networks is a challenging, but important problem. Using Quantum sources one can achieve distributions which are unattainable classically. A key point in investigations is to decide whether an observed probability distribution can be reproduced using only classical resources. This causal inference task is challenging even for simple networks, both analytically and using standard numerical techniques. We propose to use neural networks as numerical tools to overcome these challenges, by learning the classical strategies required to reproduce a distribution. As such, the neural network acts as an oracle, demonstrating that a behavior is classical if it can be learned. We apply our method to several examples in the triangle configuration. After demonstrating that the method is consistent with previously known results, we give solid evidence that the distribution presented in [N. Gisin, Entropy 21(3), 325 (2019)] is indeed nonlocal as conjectured. Finally we examine the genuinely nonlocal distribution presented in [M.-O. Renou et al., PRL 123, 140401 (2019)], and, guided by the findings of the neural network, conjecture Nonlocality in a new range of parameters in these distributions. The method allows us to get an estimate on the noise robustness of all examined distributions.
-
Quantum Nonlocality with Arbitrary Limited Detection Efficiency
Physical Review Letters, 2016Co-Authors: Gilles Pütz, Nicolas Gisin, Anthony Martin, Djeylan Aktas, Bruno Fedrici, Sébastien TanzilliAbstract:The demonstration and use of Nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detectors' inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only way to avoid this is to have detection efficiencies that are above a certain threshold. We introduce the intermediate assumption of limited detection efficiency, that is, in each run of the experiment, the overall detection efficiency is lower bounded by ηmin > 0. Hence, in an adversarial scenario, the adversaries have arbitrary large but not full control over the inefficiencies. We analyse the set of possible correlations that fulfil Limited Detection Locality (LDL) and show that they necessarily satisfy some linear Bell-like inequalities. We prove that Quantum theory predicts the violation of one of these inequalities for all ηmin > 0. Hence, non-locality can be demonstrated with arbitrarily small limited detection efficiencies. We validate this assumption experimentally via a twin-photon implementation in which two users are provided with one photon each out of a partially entangled pair. We exploit on each side a passive switch followed by two measurement devices with fixed settings. Assuming the switches are not fully controlled by an adversary, nor by hypothetical local variables, we reveal the Nonlocality of the established correlations despite a low overall detection efficiency. Introduction — When studying the discoveries in fundamental physics of the past century, one cannot help but come across Bell's seminal work on the nonlocal nature of Quantum theory [1]. It implies that Quantum physics can produce correlations which cannot be explained by a common past with local variables propagating contiguously. This has not only proven fascinating from a foundational point of view, but also given rise to applications in device independent Quantum information processing (DIQIP) [2], such as Quantum key distribution [3–5], randomness generation [6, 7], or entanglement certification [8, 9]. For a semi broad-audience presentation of these concepts, see [10]. Let us briefly recall the concept of local and nonlocal correlations. Assume that a source emits pairs of particles that travel to two distant stations, traditionally called Alice and Bob. As depicted in FIG. 1, the two ex-perimentalists perform one out of several possible measurements on the individual particles they each receive and record the associated outcomes. We denote Alice's and Bob's measurement choices by x and y and their recorded outcomes by a and b, respectively. They can then compute the correlation P (ab|xy). Given the setup, it seems natural to think that any correlations that Alice and Bob can observe in this way are due to particles having a common past, as they come from the same source. We refer to this common past by λ. Correlations that can be explained by the existence of such a parameter are called local : P L (ab|xy) =
Nicolas Brunner - One of the best experts on this subject based on the ideXlab platform.
-
a neural network oracle for Quantum Nonlocality problems in networks
npj Quantum Information, 2020Co-Authors: Tamas Krivachy, Nicolas Gisin, Daniel Cavalcanti, Yu Cai, Arash Tavakoli, Nicolas BrunnerAbstract:Characterizing Quantum Nonlocality in networks is a challenging, but important problem. Using Quantum sources one can achieve distributions which are unattainable classically. A key point in investigations is to decide whether an observed probability distribution can be reproduced using only classical resources. This causal inference task is challenging even for simple networks, both analytically and using standard numerical techniques. We propose to use neural networks as numerical tools to overcome these challenges, by learning the classical strategies required to reproduce a distribution. As such, a neural network acts as an oracle for an observed behavior, demonstrating that it is classical if it can be learned. We apply our method to several examples in the triangle configuration. After demonstrating that the method is consistent with previously known results, we give solid evidence that a Quantum distribution recently proposed by Gisin is indeed nonlocal as conjectured. Finally we examine the genuinely nonlocal distribution recently presented by Renou et al., and, guided by the findings of the neural network, conjecture Nonlocality in a new range of parameters in these distributions. The method allows us to get an estimate on the noise robustness of all examined distributions.
-
genuine Quantum Nonlocality in the triangle network
Physical Review Letters, 2019Co-Authors: Marcolivier Renou, Nicolas Gisin, Nicolas Brunner, Elisa Baumer, Sadra Boreiri, Salman BeigiAbstract:Quantum networks allow in principle for completely novel forms of Quantum correlations. In particular, Quantum Nonlocality can be demonstrated here without the need of having various input settings, but only by considering the joint statistics of fixed local measurement outputs. However, previous examples of this intriguing phenomenon all appear to stem directly from the usual form of Quantum Nonlocality, namely via the violation of a standard Bell inequality. Here we present novel examples of "Quantum Nonlocality without inputs," which we believe represent a new form of Quantum Nonlocality, genuine to networks. Our simplest examples, for the triangle network, involve both entangled states and joint entangled measurements. A generalization to any odd-cycle network is also presented.
-
a neural network oracle for Quantum Nonlocality problems in networks
arXiv: Quantum Physics, 2019Co-Authors: Tamas Krivachy, Nicolas Gisin, Daniel Cavalcanti, Yu Cai, Arash Tavakoli, Nicolas BrunnerAbstract:Characterizing Quantum Nonlocality in networks is a challenging, but important problem. Using Quantum sources one can achieve distributions which are unattainable classically. A key point in investigations is to decide whether an observed probability distribution can be reproduced using only classical resources. This causal inference task is challenging even for simple networks, both analytically and using standard numerical techniques. We propose to use neural networks as numerical tools to overcome these challenges, by learning the classical strategies required to reproduce a distribution. As such, the neural network acts as an oracle, demonstrating that a behavior is classical if it can be learned. We apply our method to several examples in the triangle configuration. After demonstrating that the method is consistent with previously known results, we give solid evidence that the distribution presented in [N. Gisin, Entropy 21(3), 325 (2019)] is indeed nonlocal as conjectured. Finally we examine the genuinely nonlocal distribution presented in [M.-O. Renou et al., PRL 123, 140401 (2019)], and, guided by the findings of the neural network, conjecture Nonlocality in a new range of parameters in these distributions. The method allows us to get an estimate on the noise robustness of all examined distributions.
-
exploring the limits of Quantum Nonlocality with entangled photons
Physical Review X, 2015Co-Authors: Bradley G Christensen, Nicolas Gisin, Nicolas Brunner, Yeong Cherng Liang, Paul G KwiatAbstract:Nonlocality is arguably among the most counterintuitive phenomena predicted by Quantum theory. In recent years, the development of an abstract theory of Nonlocality has brought a much deeper understanding of the subject, revealing a rich and complex phenomenon. In the current work, we present a systematic experimental exploration of the limits of Quantum Nonlocality. Using a versatile and high-fidelity source of pairs of polarization-entangled photons, we explore the boundary of Quantum correlations, demonstrate the counterintuitive effect of more Nonlocality with less entanglement, present the most nonlocal correlations ever reported, and achieve Quantum correlations requiring the use of complex qubits. All of our results are in remarkable agreement with Quantum predictions, and thus represent a thorough test of Quantum theory. Pursuing such an approach is nevertheless highly desirable, as any deviation may provide evidence of new physics beyond the Quantum model.
-
exploring the limits of Quantum Nonlocality with entangled photons
arXiv: Quantum Physics, 2015Co-Authors: Bradley G Christensen, Nicolas Gisin, Nicolas Brunner, Yeong Cherng Liang, Paul G KwiatAbstract:Quantum Nonlocality is arguably among the most counter-intuitive phenomena predicted by Quantum theory. In recent years, the development of an abstract theory of Nonlocality has brought a much deeper understanding of the subject. In parallel, experimental progress allowed for the demonstration of Quantum Nonlocality in a wide range of physical systems, and brings us close to a final loophole-free Bell test. Here we combine these theoretical and experimental developments in order to explore the limits of Quantum Nonlocality. This approach represents a thorough test of Quantum theory, and could provide evidence of new physics beyond the Quantum model. Using a versatile and high-fidelity source of pairs of polarization entangled photons, we explore the boundary of Quantum correlations, present the most nonlocal correlations ever reported, demonstrate the phenomenon of more Nonlocality with less entanglement, and show that non-planar (and hence complex) qubit measurements can be necessary to reproduce the strong qubit correlations that we observed. Our results are in remarkable agreement with Quantum predictions.
Taeseung Choi - One of the best experts on this subject based on the ideXlab platform.
-
Quantum probability assignment limited by relativistic causality
Scientific Reports, 2016Co-Authors: Yeong Deok Han, Taeseung ChoiAbstract:Quantum theory has nonlocal correlations, which bothered Einstein, but found to satisfy relativistic causality. Correlation for a shared Quantum state manifests itself, in the standard Quantum framework, by joint probability distributions that can be obtained by applying state reduction and probability assignment that is called Born rule. Quantum correlations, which show Nonlocality when the shared state has an entanglement, can be changed if we apply different probability assignment rule. As a result, the amount of Nonlocality in Quantum correlation will be changed. The issue is whether the change of the rule of Quantum probability assignment breaks relativistic causality. We have shown that Born rule on Quantum measurement is derived by requiring relativistic causality condition. This shows how the relativistic causality limits the upper bound of Quantum Nonlocality through Quantum probability assignment.
-
Quantum Probability assignment limited by relativistic causality
arXiv: Quantum Physics, 2013Co-Authors: Taeseung ChoiAbstract:The Quantum Nonlocality is limited by relativistic causality, however, the reason is not fully understood yet. The relativistic causality condition on nonlocal correlations has been usually accepted as a prohibition of faster-than-light signaling, called no-signaling condition. We propose another causality condition from the observation that space-like separate events should have no causal relationship. It is proved that the new condition is stronger than no-signaling condition for a pair of binary devices. We derive the standard probability assignment rule, so-called Born rule, on Quantum measurement, which determines the degree of Quantum Nonlocality, by using relativistic causality constraint. This shows how the causality limits the upper bound of Quantum Nonlocality through Quantum probability assignment.
Yeong Cherng Liang - One of the best experts on this subject based on the ideXlab platform.
-
exploring the limits of Quantum Nonlocality with entangled photons
Physical Review X, 2015Co-Authors: Bradley G Christensen, Nicolas Gisin, Nicolas Brunner, Yeong Cherng Liang, Paul G KwiatAbstract:Nonlocality is arguably among the most counterintuitive phenomena predicted by Quantum theory. In recent years, the development of an abstract theory of Nonlocality has brought a much deeper understanding of the subject, revealing a rich and complex phenomenon. In the current work, we present a systematic experimental exploration of the limits of Quantum Nonlocality. Using a versatile and high-fidelity source of pairs of polarization-entangled photons, we explore the boundary of Quantum correlations, demonstrate the counterintuitive effect of more Nonlocality with less entanglement, present the most nonlocal correlations ever reported, and achieve Quantum correlations requiring the use of complex qubits. All of our results are in remarkable agreement with Quantum predictions, and thus represent a thorough test of Quantum theory. Pursuing such an approach is nevertheless highly desirable, as any deviation may provide evidence of new physics beyond the Quantum model.
-
exploring the limits of Quantum Nonlocality with entangled photons
arXiv: Quantum Physics, 2015Co-Authors: Bradley G Christensen, Nicolas Gisin, Nicolas Brunner, Yeong Cherng Liang, Paul G KwiatAbstract:Quantum Nonlocality is arguably among the most counter-intuitive phenomena predicted by Quantum theory. In recent years, the development of an abstract theory of Nonlocality has brought a much deeper understanding of the subject. In parallel, experimental progress allowed for the demonstration of Quantum Nonlocality in a wide range of physical systems, and brings us close to a final loophole-free Bell test. Here we combine these theoretical and experimental developments in order to explore the limits of Quantum Nonlocality. This approach represents a thorough test of Quantum theory, and could provide evidence of new physics beyond the Quantum model. Using a versatile and high-fidelity source of pairs of polarization entangled photons, we explore the boundary of Quantum correlations, present the most nonlocal correlations ever reported, demonstrate the phenomenon of more Nonlocality with less entanglement, and show that non-planar (and hence complex) qubit measurements can be necessary to reproduce the strong qubit correlations that we observed. Our results are in remarkable agreement with Quantum predictions.
-
arbitrarily small amount of measurement independence is sufficient to manifest Quantum Nonlocality
Physical Review Letters, 2014Co-Authors: Gilles Pütz, Yeong Cherng Liang, Denis Rosset, Tomer Jack Barnea, Nicolas GisinAbstract:The use of Bell's theorem in any application or experiment relies on the assumption of free choice or, more precisely, measurement independence, meaning that the measurements can be chosen freely. Here, we prove that even in the simplest Bell test-one involving 2 parties each performing 2 binary-outcome measurements-an arbitrarily small amount of measurement independence is sufficient to manifest Quantum Nonlocality. To this end, we introduce the notion of measurement dependent locality and show that the corresponding correlations form a convex polytope. These correlations can thus be characterized efficiently, e.g., using a finite set of Bell-like inequalities-an observation that enables the systematic study of Quantum Nonlocality and related applications under limited measurement independence.
-
anonymous Quantum Nonlocality
Physical Review Letters, 2014Co-Authors: Yeong Cherng Liang, Florian J Curchod, Joseph Bowles, Nicolas GisinAbstract:We investigate the phenomenon of anonymous Quantum Nonlocality, which refers to the existence of multipartite Quantum correlations that are not local in the sense of being Bell-inequality-violating but where the Nonlocality is---due to its biseparability with respect to all bipartitions---seemingly nowhere to be found. Such correlations can be produced by the nonlocal collaboration involving definite subset(s) of parties but to an outsider, the identity of these nonlocally correlated parties is completely anonymous. For all $n\ensuremath{\ge}3$, we present an example of an $n$-partite Quantum correlation exhibiting anonymous Nonlocality derived from the $n$-partite Greenberger-Horne-Zeilinger state. An explicit biseparable decomposition of these correlations is provided for any partitioning of the $n$ parties into two groups. Two applications of these anonymous Greenberger-Horne-Zeilinger correlations in the device-independent setting are discussed: multipartite secret sharing between any two groups of parties and bipartite Quantum key distribution that is robust against nearly arbitrary leakage of information.
-
detecting genuine multipartite Quantum Nonlocality a simple approach and generalization to arbitrary dimensions
Physical Review Letters, 2011Co-Authors: Jeandaniel Bancal, Nicolas Gisin, Nicolas Brunner, Yeong Cherng LiangAbstract:The structure of Bell-type inequalities detecting genuine multipartite Nonlocality, and hence detecting genuine multipartite entanglement, is investigated. We first present a simple and intuitive approach to Svetlichny's original inequality, which provides a clear understanding of its structure and of its violation in Quantum mechanics. Based on this approach, we then derive a family of Bell-type inequalities for detecting genuine multipartite Nonlocality in scenarios involving an arbitrary number of parties and systems of arbitrary dimension. Finally, we discuss the tightness and Quantum mechanical violations of these inequalities.
Anton Zeilinger - One of the best experts on this subject based on the ideXlab platform.
-
experimental Nonlocality proof of Quantum teleportation and entanglement swapping
Physical Review Letters, 2001Co-Authors: Thomas Jennewein, Gregor Weihs, Jianwei Pan, Anton ZeilingerAbstract:Quantum teleportation strikingly underlines the peculiar features of the Quantum world. We present an experimental proof of its Quantum nature, teleporting an entangled photon with such high quality that the nonlocal Quantum correlations with its original partner photon are preserved. This procedure is also known as entanglement swapping. The Nonlocality is confirmed by observing a violation of Bell's inequality by 4.5 standard deviations. Thus, by demonstrating Quantum Nonlocality for photons that never interacted, our results directly confirm the Quantum nature of teleportation.
-
experimental demonstration of four photon entanglement and high fidelity teleportation
Physical Review Letters, 2001Co-Authors: Jianwei Pan, Gregor Weihs, Matthew Daniell, Sara Gasparoni, Anton ZeilingerAbstract:We experimentally demonstrate observation of highly pure four-photon GHZ entanglement produced by parametric down-conversion and a projective measurement. At the same time this also demonstrates teleportation of entanglement with very high purity. Not only does the achieved high visibility enable various novel tests of Quantum Nonlocality, it also opens the possibility to experimentally investigate various Quantum computation and communication schemes with linear optics. Our technique can, in principle, be used to produce entanglement of arbitrarily high order or, equivalently, teleportation and entanglement swapping over multiple stages.
-
experimental test of Quantum Nonlocality in three photon greenberger horne zeilinger entanglement
Nature, 2000Co-Authors: Jianwei Pan, Matthew Daniell, Dik Bouwmeester, Harald Weinfurter, Anton ZeilingerAbstract:Bell's theorem states that certain statistical correlations predicted by Quantum physics for measurements on two-particle systems cannot be understood within a realistic picture based on local properties of each individual particle-even if the two particles are separated by large distances. Einstein, Podolsky and Rosen first recognized the fundamental significance of these Quantum correlations (termed 'entanglement' by Schrodinger) and the two-particle Quantum predictions have found ever-increasing experimental support. A more striking conflict between Quantum mechanical and local realistic predictions (for perfect correlations) has been discovered; but experimental verification has been difficult, as it requires entanglement between at least three particles. Here we report experimental confirmation of this conflict, using our recently developed method to observe three-photon entanglement, or 'Greenberger-Horne-Zeilinger' (GHZ) states. The results of three specific experiments, involving measurements of polarization correlations between three photons, lead to predictions for a fourth experiment; Quantum physical predictions are mutually contradictory with expectations based on local realism. We find the results of the fourth experiment to be in agreement with the Quantum prediction and in striking conflict with local realism.
