12,868 research outputs found
Enhanced quantum teleportation in the background of Schwarzschild spacetime by weak measurements
It is commonly believed that the fidelity of quantum teleportation in the
gravitational field would be degraded due to the heat up by the Hawking
radiation. In this paper, we point out that the Hawking effect could be
eliminated by the combined action of pre- and post-weak measurements, and thus
the teleportation fidelity is almost completely protected. It is intriguing to
notice that the enhancement of fidelity could not be attributed to the
improvement of entanglement, but rather to the probabilistic nature of weak
measurements. Our work extends the ability of weak measurements as a quantum
technique to battle against gravitational decoherence in relativistic quantum
information.Comment: 9 pages, 5 figures, comments are welcom
Scalable Bell inequalities for multiqubit systems
Based on Clauser-Horner-Shimony-Holt inequality, we show a fruitful method to
exploit Bell inequalities for multipartite qubit systems. These Bell
inequalities are designed with a simpler architecture tailored to experimental
demonstration. Under the optimal setting we derive a set of compact Mermin-type
inequalities and discuss quantum violations for generalized
Greenberger-Horne-Zeilinger (GGHZ) states. Also, we reveal relationship between
quantum nonlocality and four-partite entanglement for four-qubit GGHZ states.Comment: 4 pages, 1 figur
Robust Spin Squeezing Preservation in Photonic Crystal Cavities
We show that the robust spin squeezing preservation can be achieved by
utilizing detuning modification for an ensemble of N separate two-level atoms
embedded in photonic crystal cavities (PCC). In particular, we explore the
different dynamical behaviors of spin squeezing between isotropic and
anisotropic PCC cases when the atomic frequency is inside the band gap. In both
cases, it is shown that the robust preservation of spin squeezing is completely
determined by the formation of bound states. Intriguingly, we find that unlike
the isotropic case where steady-state spin squeezing varies smoothly when the
atomic frequency moves from the inside to the outside band edge, a sudden
transition occurs for the anisotropic case. The present results may be of
direct importance for, e.g., quantum metrology in open quantum systems.Comment: 6 pages, 4 figures, accepted by Laser Physics Letter
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