3/4-efficient Bell measurement with passive linear optics and unentangled ancillae

未纠缠光子表观贝尔非定域性的简单解释

Simple explanation of apparent Bell nonlocality of unentangled photons

本研究针对Wang等人声称用未纠缠光子实现贝尔不等式违反的争议性实验，通过简化理想场景分析，指出表观违反源于后选择与非常规归一化，并非真正的无纠缠非定域性，而是对多光子干涉效应的误读。

Bell correlations from local unentangled states of light and quantum electrodynamics

Based on the Bell theorem, it has been believed that a theoretical computation of the Bell correlation requires explicit use of an entangled state. Such a physical superposition of light waves occurs in the downconverter sources used in Bell experiments. However, this physical superposition is eliminated by wave propagation to spatially separated detectors. Bell correlations must therefore result from local waves, and the source boundary conditions of their previously entangled state. In the present model, Bell correlations are computed from disentangled separated waves, boundary conditions of…

Approaching near-perfect state discrimination of photonic Bell states through the use of unentangled ancilla photons

Despite well-established no-go theorems on a perfect linear optical Bell state analyzer, we find a numerical trend that appears to approach a near-perfect measurement if we incorporate eight or more un-entangled ancilla photons into our device. Following this trend, we begin a promising inductive approach to building an ideal optical Bell measurement device. In the process, we determine that any Bell state analyzer that (even occasionally) bunches all photons into only two of the output modes cannot perform an ideal measurement and we find a set of conditions on our linear optical circuit that…

Linear-optical implementations of the iSWAP and controlled NOT gates based on conventional detectors

The majority of linear-optical nondestructive implementations of universal quantum gates are based on single-photon resolving detectors. We propose two implementations, which are nondestructive (i.e., destroying only ancilla states) and work with conventional detectors (i.e., which do not resolve number of photons). Moreover, we analyze a recently proposed scheme of Wang et al. [J. Opt. Soc. Am. B \textbf{27}, 27 (2010)] of an optical iSWAP gate based on two ancillae in Bell's states, classical feedforward, and conventional detectors with the total probability of success equal to $η^4/32$, whe…

违反贝尔不等式与非纠缠光子

Violation of Bell Inequality with Unentangled Photons

研究通过多光子受阻干涉揭示量子不可区分性导致的贝尔不等式违反，突破传统纠缠概念，展示量子关联与不可区分性的联系。

Short Multi-Prover Quantum Proofs for SAT without Entangled Measurements

BellQMA protocols are a subclass of multi-prover quantum Merlin-Arthur protocols in which the verifier is restricted to perform nonadaptive,unentangled measurements on the quantum states received from each Merlin. In this paper, we prove that m-clause 3-SAT instances have BellQMA proofs of satisfiability with constant soundness gap, in which O(sqrt(m)polylog(m)) Merlins each send O(log m) qubits to Arthur. Our result answers a question of Aaronson et al., who gave a protocol with similar parameters that used entangled measurements; the analysis of our protocol is significantly simpler than tha…