Protecting quantum coherence in an open system under non-inertial frames

2017 ◽  
Vol 31 (35) ◽  
pp. 1750336
Author(s):  
Long-Fei Wang ◽  
Ming-Ming Du ◽  
Liu Ye
Keyword(s):  
Open System ◽  
Significant Interaction ◽  
Quantum Coherence ◽  
Weak Measurement ◽  
Entangled State ◽  
Unruh Effect ◽  
Amplitude Damping ◽  
Inertial Frames ◽  
Weak Measurement And Reversal

In this paper, we explore the dynamics and protection of quantum coherence in an open system under non-inertial frames by weak measurement and reversal, and design four strategies to protect the quantum coherence of an initial two-qubit entangled state, when the systems suffer from amplitude damping (AD) channel and one subsystem is under non-inertial frames. In practice, there is no strict inertial frames, decoherence and degradation of the quantum coherence caused by the Unruh effect form acceleration will have a significant interaction, therefore it is important to find some means to protect quantum coherence under non-inertial frames.

scholarly journals Measurement of entropy and quantum coherence properties of two type-I entangled photonic qubits

2021 ◽  
Vol 53 (7) ◽  
Author(s):  
Ali Motazedifard ◽  
Seyed Ahmad Madani ◽  
N. S. Vayaghan
Keyword(s):  
Maximum Likelihood ◽  
Quantum Coherence ◽  
Single Photon ◽  
Bell Inequality ◽  
Bell State ◽  
Von Neumann Entropy ◽  
Entangled State ◽  
Type I ◽  
Variable Theory ◽  
High Brightness

AbstractUsing the type-I SPDC process in BBO nonlinear crystal, we generate a polarization-entangled state near to the maximally-entangled Bell-state with high-visibility (high-brightness) 98.50 ± 1.33% (87.71 ± 4.45%) for HV (DA) basis. We calculate the CHSH version of the Bell inequality, as a nonlocal realism test, and find a strong violation from the classical physics or any hidden variable theory, S = 2.71 ± 0.10. Via measuring the coincidence count rate in the SPDC process, we obtain the quantum efficiency of single-photon detectors around (25.5 ± 3.4)%, which is in good agreement to their manufacturer company. As expected, we verify the linear dependency of the CC rate vs. pump power of input CW-laser, which may yield to find the effective second-order susceptibility crystal. Using the theory of the measurement of qubits, includes a tomographic reconstruction of quantum states due to the linear set of 16 polarization-measurement, together with a maximum-likelihood-technique, which is based on the numerical optimization, we calculate the physical non-negative definite density matrices, which implies on the non-separability and entanglement of prepared state. By having the maximum likelihood density operator, we calculate precisely the entanglement measures such as Concurrence, entanglement of formation, tangle, logarithmic negativity, and different entanglement entropies such as linear entropy, Von-Neumann entropy, and Renyi 2-entropy. Finally, this high-brightness and low-rate entangled photons source can be used for short-range quantum measurements in the Lab.

ON THE ENTANGLED STATE REPRESENTATION, EXCITATION REPRESENTATION AND EFFECTIVE NUMBER-PHASE STATE REPRESENTATIONS IN RINDLER SPACE

2004 ◽  
Vol 19 (34) ◽  
pp. 2587-2594 ◽  
Author(s):  
HONG-YI FAN ◽  
HAI-YAN HE
Keyword(s):  
Phase State ◽  
Vacuum State ◽  
Point Of View ◽  
Entangled State ◽  
Unruh Effect ◽  
Entangled State Representation ◽  
Effective Number ◽  
State Representation ◽  
Commutative Relation ◽  
Rindler Space

We analyze the Unruh effect from the point of view of quantum entanglement. We introduce the entangled state representation in Rindler space and show that the Minkowski vacuum state is an entangled state in Rindler space. The corresponding squeezing operator, which is related to the acceleration of the detector, is obtained naturally. The excitation representation and number state–phase state representations are also introduced in Rindler space. The number-phase commutative relation is established.

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