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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Experimental Violation of Bell's Inequality for Temporal Orders
摘要： Entanglement is a prediction of quantum mechanics that suggests that our physical laws cannot be described by a local causal model. This has led to much debate, including Einstein’s famous suggestion that quantum mechanics is an incomplete theory, and we may one day discover a deeper theory that can be described by a locally causal model. However, loophole free violations of Bell inequalities demonstrate that this is not the case. Bell’s theorem is independent of quantum mechanics, and it shows that any theory attempting to supplant quantum mechanics must be somehow nonlocal. Since then, there have been many experimental violations of Bell inequalities using different physical systems, culminating in three loophole-free experiments [1-3]. Very recent theoretical [4, 5] and experimental techniques [6, 7] have enabled the study of a new phenomenon predicted by quantum mechanics. Namely, the existence of processes without a fixed causal order. Previous experimental tests of this effect, required the assumption that quantum mechanics can be used to correctly model the experimental results. However, just as the study of entanglement before Bell, these results could still be described by some other theory in which the causal order is definite. The question, then, naturally arises do such processes really exist, or are they an artefact of the quantum mechanics. Here we show that these effects are indeed real by constructing a Bell inequality for temporal orders [8]. The violation of this equality implies, independent of quantum mechanics, that the temporal order of the process under study must have been truly indefinite. We then show we can violate this inequality using a system consisting of two quantum SWITCHes [6,7] with entangled control qubits (see Fig. 1).
关键词： quantum mechanics,Bell’s inequality,quantum SWITCH,entanglement,temporal order
更新于2025-09-16 10:30:52
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Time dependent correlations of entangled states with nondegenerate branches and possible experimental realization using singlet fission
摘要： The spin-entangled exciton states produced by singlet fission provide an experimental route to generate entangled states with nondegenerate branches. Nondegenerate entangled pair states possess an internal "clock" that leads to quantum beating in various detected quantities. The implications of this internal clock for Bell’s inequality measurements and correlated particle detection are analyzed using two- and three-state spin models. In a Bell’s inequality experiment, we find that the choice of detection times can determine whether quantum or classical correlations are observed. The conditions under which the detection events could be time- or spacelike separated are analyzed in order to clarify how the temporal evolution of one particle can influence the time-dependent detection probability of the other. Possible routes to the detection of individual correlated triplet excitons are discussed, emphasizing both physical questions concerning the separation and propagation of triplet excitons over macroscopic distances and experimental challenges concerning decoherence, detection, and interpretation of the signals. We argue that spin-entangled triplet exciton states produced by singlet fission could provide a new way to probe entangled state detection and collapse, complementing schemes based on polarization-entangled photon states.
关键词： detection,Bell’s inequality,correlated particle detection,spin-entangled exciton states,nondegenerate branches,triplet excitons,quantum beating,singlet fission,decoherence
更新于2025-09-12 10:27:22