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Bipartite Bell inequalities with three ternary-outcome measurements—from theory to experiments
摘要： We explore quantum nonlocality in one of the simplest bipartite scenarios. Several new facet-defining Bell inequalities for the {[3,3,3],[3,3,3]} scenario are obtained with their quantum violations analyzed in details. Surprisingly, all these inequalities involving only genuine ternary-outcome measurements can be violated maximally by some two-qubit entangled states, such as the maximally entangled two-qubit state. This gives further evidence that in analyzing the quantum violation of Bell inequalities, or in the application of the latter to device-independent quantum information processing tasks, the commonly held wisdom of equating the local Hilbert space dimension of the optimal state with the number of measurement outcomes is not necessarily justifiable. In addition, when restricted to the minimal qubit subspace, it can be shown that one of these Bell inequalities requires non-projective measurements to attain maximal quantum violation, thereby giving the first example of a facet-defining Bell inequality where a genuine positive-operator-valued measure is relevant. We experimentally demonstrate the quantum violation of this and two other Bell inequalities for this scenario using energy–time entangled photon pairs. Using the obtained measurement statistics, we demonstrate how characterization of the underlying resource in the spirit of device-independence, but supplemented with auxiliary assumptions, can be achieved. In particular, we discuss how one may get around the fact that, due to finite-size effects, raw measurement statistics typically violate the non-signaling condition.
关键词： quantum nonlocality,device-independent quantum information,POVM,Bell inequalities
更新于2025-09-23 15:23:52
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Generation of solitons in media with arbitrary degree of nonlocality using an optimization procedure
摘要： Using a recently developed technique based on the Rayleigh-Ritz optimization principle, we generate solitons for media with an arbitrary degree of nonlocality. We demonstrate that it is possible to obtain a plethora of complex self-trapped beams using known solutions to the harmonic oscillator for one-dimensional (1D), 2D, and 3D systems, but working directly with a generalized nonlinear nonlocal Schr?dinger equation. We compare the parameters obtained variationally between the phenomenological Gaussian response and other more realistic nonlocal responses. We report that, for both kinds of nonlocal models, our approach obtains variational solutions that can remain self-trapped for certain conditions. We corroborate that, in general, the soliton dynamics can be different between the Gaussian response and the more realistic media for an arbitrary degree of nonlocality.
关键词： nonlinear Schr?dinger equation,variational approximation,nonlocality,solitons,optical beams
更新于2025-09-23 15:22:29
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Aperiodic order induced enhancement of weak nonlocality in multilayered dielectric metamaterials
摘要： Recent studies on fully dielectric multilayered metamaterials have shown that the negligibly small nonlocal effects (spatial dispersion) typically observed in the limit of deeply subwavelength layers may be significantly enhanced by peculiar boundary effects occurring in certain critical parameter regimes. These phenomena, observed so far in periodic and randomly disordered geometries, are manifested as strong differences between the exact optical response of finite-size metamaterial samples and the prediction from conventional effective-theory-medium models based on mixing formulas. Here, with specific focus on the Thue-Morse geometry, we make a first step toward extending the studies above to the middle ground of aperiodically ordered multilayers, lying in between perfect periodicity and disorder. We show that, also for these geometries, there exist critical parameter ranges that favor the buildup of boundary effects leading to strong enhancement of the (otherwise negligibly weak) nonlocality. However, the underlying mechanisms are fundamentally different from those observed in the periodic case and exhibit typical footprints (e.g., fractal gaps, quasilocalized states) that are distinctive of aperiodic order. The outcomes of our study indicate that aperiodic order plays a key role in the buildup of the aforementioned boundary effects and may also find potential applications to optical sensors, absorbers, and lasers.
关键词： absorbers,optical sensors,lasers,Thue-Morse geometry,aperiodic order,multilayered dielectric metamaterials,nonlocality
更新于2025-09-23 15:21:21
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Geometrical self-testing of partially entangled two-qubit states
摘要： Quantum nonlocality has recently been intensively studied in connection to device-independent quantum information processing, where the extremal points of the set of quantum correlations play a crucial role through self-testing. In most protocols, the proofs for self-testing rely on the maximal violation of the Bell inequalities, but there is another known proof based on the geometry of state vectors to self-test a maximally entangled state. We present a geometrical proof in the case of partially entangled states. We show that, when a set of correlators in the simplest Bell scenario satisfies a condition, the geometry of the state vectors is uniquely determined. The realization becomes self-testable when another unitary observable exists on the geometry. Applying this proven fact, we propose self-testing protocols by intentionally adding one more measurement. This geometrical scheme for self-testing is superior in that, by using this as a building block and repeatedly adding measurements, a realization with an arbitrary number of measurements can be self-tested. Besides the application, we also attempt to describe nonlocal correlations by guessing probabilities of distant measurement outcomes. In this description, the quantum set is also convex, and a large class of extremal points is identified by the uniqueness of the geometry.
关键词： device-independent quantum information processing,Bell inequality,quantum nonlocality,self-testing
更新于2025-09-23 15:21:01
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Alternative method for deriving nonlocal multipartite product states
摘要： We can only perform finite rounds of measurements in protocols with local operations and classical communication (LOCC). In this paper, we propose a set of product states that require infinite rounds of measurements in order to distinguish this given set of states perfectly by LOCC. Therefore, we can conclude that these sets of states are locally indistinguishable. More accurately, given any multipartite LOCC indistinguishable set where every local system cannot start with a nontrivial measurement, then after appending these states with arbitrarily choosing two nonorthogonal states, we obtain another LOCC indistinguishable set. It can be seen that some parties can perform some nontrivial measurements. Hence, these sets are quite different from those constructed before. This result broadens the knowledge of nonlocality without entanglement to a certain extent.
关键词： entanglement,LOCC,product states,quantum information,nonlocality
更新于2025-09-23 15:21:01
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Closing the Door on Quantum Nonlocality
摘要： Bell-type inequalities are proven using oversimpli?ed probabilistic models and/or counterfactual de?niteness (CFD). If setting-dependent variables describing measuring instruments are correctly introduced, none of these inequalities may be proven. In spite of this, a belief in a mysterious quantum nonlocality is not fading. Computer simulations of Bell tests allow people to study the different ways in which the experimental data might have been created. They also allow for the generation of various counterfactual experiments’ outcomes, such as repeated or simultaneous measurements performed in different settings on the same ‘’photon-pair”, and so forth. They allow for the reinforcing or relaxing of CFD compliance and/or for studying the impact of various “photon identi?cation procedures”, mimicking those used in real experiments. Data samples consistent with quantum predictions may be generated by using a speci?c setting-dependent identi?cation procedure. It re?ects the active role of instruments during the measurement process. Each of the setting-dependent data samples are consistent with speci?c setting-dependent probabilistic models which may not be deduced using non-contextual local realistic or stochastic hidden variables. In this paper, we will be discussing the results of these simulations. Since the data samples are generated in a locally causal way, these simulations provide additional strong arguments for closing the door on quantum nonlocality.
关键词： photon identi?cation loophole,Bell-inequalities,quantum nonlocality,local causality,computer simulations of Bell tests,contextuality loophole
更新于2025-09-23 15:21:01
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Electromagnetically induced grating in semiconductor quantum dot and metal nanoparticle hybrid system by considering nonlocality effects
摘要： The optical polarization from a hybrid system including a closely spaced spherical SQD (modeled as a three-level V-type system) and a metal nanoparticle which are considered classically and are connected by the dipole–dipole interaction mechanism is investigated. The interaction between the SQD and the MNP shows an interesting optical response. In the weak probe field regime and MNP nonlocality correction, the absorption spectrum of the hybrid system exhibits an EIT window with two absorption peaks and the plasmon-assisted quantum interference plays an important role in the position and amplitude of these peaks, which are intensely altered by including the nonlocal effects. The probe diffraction grating is created based on the excitons-induced transparency by applying a standing-wave coupling field. The results of this study are useful in numerous areas of all-optical communications.
关键词： Metal nanoparticles (MNP),Hybrid system,Electromagnetically induced grating (EIG),Nonlocality,Semiconductor quantum dot (SQD)
更新于2025-09-23 15:19:57
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Discrete Source Method for the Study of Influence Nonlocality on Characteristics of the Plasmonic Nanolaser Resonators
摘要： The discrete source method is generalized so as to investigate the nonlocal effects in multilayered particles on a substrate. The scheme for constructing an approximate solution and the corresponding numerical algorithm are described in detail. The developed approach is used to study the optical characteristics of 3D cavities of plasmonic nanolasers. It is shown that the amplitude of surface plasmon resonance and the amplification factor of the near-field intensity are reduced significantly when the nonlocal effects are taken into account. It is also shown that the amplification factor can be increased by more than twice by varying the material and thickness of the cavity shell and the direction of the incident wave.
关键词： nanoplasmonics,quantum effect of nonlocality,discrete source method,plasmonic nanolaser (spaser)
更新于2025-09-23 15:19:57
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Local distinguishability of orthogonal quantum states with no more than one ebit of entanglement
摘要： In this paper, we study the local distinguishability of mutually orthogonal product quantum states with entanglement as a valuable resource. We present protocols in which entanglement is used more efficiently than in the previous protocols presented by Zhang et al. [Phys. Rev. A 97, 022334 (2018)]. Specifically, the main technical contributions are as follows: First, we present a method to locally distinguish a set of orthogonal product quantum states in d ? d (d is odd) by using only one ancillary two-qubit maximally entangled state. Then we present a similar method to locally distinguish multipartite orthogonal product states by using entanglement efficiently. Moreover, we propose a method to study the local distinguishability of this kind of orthogonal product state with less than one ebit of entanglement, and analyze the relationship between the probability of error and the quantity of entanglement, which reveals the phenomenon of less nonlocality with more entanglement.
关键词： LOCC,orthogonal quantum states,nonlocality,local distinguishability,entanglement
更新于2025-09-19 17:15:36
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Operational symmetries of entangled states
摘要： Quantum entanglement obscures the notion of local operations; there exist quantum states for which all local actions on one subsystem can be equivalently realized by actions on another. We characterize the states for which this fundamental property of entanglement does and does not hold, including multipartite and mixed states. Our results lead to a method for quantifying entanglement based on operational symmetries and has connections to quantum steering, envariance, the Reeh–Schlieder theorem, and classical entanglement.
关键词： entanglement manipulation,entanglement in field theory,quantum entanglement,entanglement measures,quantum nonlocality
更新于2025-09-19 17:13:59