Quantum indistinguishability by path identity generates a new way of optical coherence, called ``induced coherence". The phenomenon, originally uncovered by Zou, Wang, and Mandel's experiment, is an emerging notion in modern quantum experiments with a wide range of implications. However, there has been controversy over its true quantum nature and whether the result can be emulated with classical light. We design a suitable contextuality test that can determine the conditions under which the setting produces distinguishing quantum predictions that cannot be described classically, namely, via the noncontextual hidden variable model.
Contextuality is an indicator of non-classicality, and a resource for various quantum procedures. In this paper, we use contextuality to evaluate the variational quantum eigensolver (VQE), one of the most promising tools for near-term quantum simulation. We present an efficiently computable test to determine whether or not the objective function for a VQE procedure is contextual. We apply this test to evaluate the contextuality of experimental implementations of VQE, and determine that several, but not all, fail this test of quantumness.
Contextuality, superlocality and nonclassicality of supernoncontextuality
National Cheng Kung University（国立成功大学）；National Center for Theoretical Sciences, National Taiwan University（台湾大学国家理论科学中心）；Poornaprajna Institute of Scientific Research (PPISR)（普尔纳普拉吉纳科学研究学院）
Contextuality is a signature of operational nonclassicality in the outcome statistics of an experiment. This notion of nonclassicality applies to a breadth of physical phenomena. Here, we establish its relation to two fundamental nonclassical entities in quantum theory; measurement incompatibility and steering. We show that each is necessary and sufficient the failure of operational contextuality. We exploit the established connection to contextuality to provide a novel approach to problems in measurement incompatibility and steering.
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 $\mathfrak{su…
The Kochen--Specker (KS) theorem reveals the nonclassicality of single quantum systems. In contrast, Bell's theorem and entanglement concern the nonclassicality of composite quantum systems. Accordingly, unlike incompatibility, entanglement and Bell non-locality are not necessary to demonstrate KS-contextuality. However, here we find that for multiqubit systems, entanglement and non-locality are both essential to proofs of the Kochen--Specker theorem. Firstly, we show that unentangled measurements (a strict superset of local measurements) can never yield a logical (state-independent) proof of …
We identify a fundamental difference between classical and quantum dynamics in the linear response regime by showing that the latter is in general contextual. This allows us to provide an example of a quantum engine whose favorable power output scaling \emph{unavoidably} requires nonclassical effects in the form of contextuality. Furthermore, we describe contextual advantages for local metrology. Given the ubiquity of linear response theory, we anticipate that these tools will allow one to certify the nonclassicality of a wide array of quantum phenomena.
Theory-independent monitoring of the decoherence of a superconducting qubit with generalized contextuality
Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences（奥地利科学院量子光学与量子信息研究所）；Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna（维也纳大学物理学院维也纳量子科学与技术中心）；Department of Physics, ETH Zürich（苏黎世联邦理工学院物理系）；Perimeter Institute for Theoretical Physics（基础物理研究所）
How Quantum Contextuality disappears in the Classical Limit
Instituto de Matemática, Estatística e Computação Científica, Universidade Estadual de Campinas（坎皮纳斯州立大学数学、统计与科学计算研究所）；Perimeter Institute for Theoretical Physics（理论物理前沿研究所）
Contextuality is one way of capturing the non-classicality of quantum theory. The contextual nature of a theory is often witnessed via the violation of non-contextuality inequalities---certain linear inequalities involving probabilities of measurement events. Using the exclusivity graph approach (one of the two main graph theoretic approaches for studying contextuality), it was shown [PRA 88, 032104 (2013); Annals of mathematics, 51-299 (2006)] that a necessary and sufficient condition for witnessing contextuality is the presence of an odd number of events (greater than three) which are either…
International Centre for Theory of Quantum Technologies, University of Gdańsk（格但斯克大学量子技术理论国际中心）；Perimeter Institute for Theoretical Physics（基础物理研究所）；Basic Research Community for Physics e.V.（基础物理社区协会）
Theory-agnostic nonclassicality certification in an integrated photonic circuit
University of Gdańsk（格但斯克大学）；Griffith University（格里菲斯大学）；Sapienza Università di Roma（罗马大学）；Sparrow Quantum（麻雀量子）；Perimeter Institute for Theoretical Physics（理论物理柏拉图研究所）；Consiglio Nazionale delle Ricerche（意大利国家研究委员会）；Politecnico di Milano（米兰理工大学）
上下文性是量子力学的一个重要特征，它为量子信息和计算提供了重要的非经典资源。Abramsky和Brandenburger使用层理论对量子理论中的上下文性进行了一般性处理[New Journal of Physics 13（2011）113036]。然而，在其他领域也发现了上下文现象，例如数据库理论。在本文中，我们将发展这种统一的语境观。我们提供了两个主要的贡献：首先，我们揭示了显着的上下文和逻辑悖论之间的连接;其次，我们表明，一类重要的上下文参数具有拓扑起源。更具体地说，我们表明，“全对无”的上下文证明是见证了同调障碍。
Quantum key distribution using generalized contextuality against post-quantum eavesdroppers
Perimeter Institute for Theoretical Physics；Department of Physics and Astronomy, University of Waterloo（滑铁卢大学物理与天文系）；Institute for Quantum Computing, University of Waterloo（滑铁卢大学量子计算研究所）
Coherence as a resource for $N$-box and quantum pigeonhole paradoxes
INL – International Iberian Nanotechnology Laboratory（国际伊比利亚纳米技术实验室）；Institute of Theoretical Physics, Ulm University（乌尔姆大学理论物理研究所）；Center for Integrated Quantum Science and Technology (IQST)（集成量子科学与技术中心）；Instituto de Física, Universidade Federal Fluminense（弗鲁米嫩塞联邦大学物理研究所）
The interplay between the nonclassical features and the parity-time (PT) symmetry (or its breaking) is studied here by considering a PT symmetric system consisting of two cavities with gain and loss. The conditions for PT invariance is obtained for this system. The behavior of the average photon number corresponding to the gain and loss modes for different initial states (e.g., vacuum, NOON, coherent, and thermal states) has also been obtained. With the help of the number operators, quantum Zeno and anti-Zeno effects are studied, and the observed behavior is compared in PT symmetric (PTS) and …
