scholarly journals Coherent State Control to Recover Quantum Entanglement and Coherence

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 917
Author(s):  
Li-Tuo Shen ◽  
Zhi-Cheng Shi ◽  
Zhen-Biao Yang
Keyword(s):  
Continuous Variable ◽  
State Control ◽  
Entanglement Dynamics ◽  
Maximal Entanglement ◽  
Fock State ◽  
Analytical Formulas ◽  
X State ◽  
Open Question ◽  
Limit Approximation ◽  
Common Situation

How to analytically deal with the entanglement and coherence dynamics of separated Jaynes–Cummings nodes with continuous-variable fields is still an open question. We here generalize this model to a more common situation including either a small or large qubit-field detuning, and obtain two new analytical formulas. The X-state simplification, Fock-state shortcut and detuning-limit approximation work together in an amazingly accurate way, which agrees with the numerical results. The new formulas almost perfectly predict the two-qubit entanglement dynamics both in sudden death and rebirth phenomenon for detuning interactions. We find that when both the qubit-field detuning and amplitude of coherent states are large enough, the maximal entanglement and coherence peaks can be fully and periodically retrieved, and their revival periods both increase linearly with the increasing detuning.

INFLUENCE OF INTRINSIC DECOHERENCE ON THE ENTANGLEMENT BETWEEN TWO ATOMS IN TAVIS–CUMMINGS MODEL

2008 ◽  
Vol 06 (01) ◽  
pp. 167-179
Author(s):  
CHUAN-JIA SHAN ◽  
WEI-WEN CHENG ◽  
TANG-KUN LIU ◽  
YAN-XIA HUANG ◽  
HONG LI ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Quantum State ◽  
Dipole Interaction ◽  
Entangled State ◽  
Entanglement Dynamics ◽  
Initial State ◽  
Intrinsic Decoherence ◽  
Dipole Coupling ◽  
Fock State

Considering the dipole–dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the Tavis–Cummings model with intrinsic decoherence have been investigated. The two-atom entanglement appears with periodicity without considering intrinsic decoherence. However, the intrinsic decoherence causes the decay of entanglement between two atoms, with the decrease of the intrinsic decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state, the dipole–dipole coupling intensity and the field in the Fock state. Meanwhile, the two-atom quantum state will stay forever in the maximal entangled state when the initial state is proper, even in the presence of intrinsic decoherence. Furthermore, the two atoms can generate maximal entangled state even if they are initially separated by adjusting the dipole–dipole interaction, the strong coupling can improve the value of entanglement.

scholarly journals Photonic hybrid state entanglement swapping using cat state superpositions

2020 ◽  
Vol 476 (2243) ◽  
pp. 20200237
Author(s):  
Ryan C. Parker ◽  
Jaewoo Joo ◽  
Timothy P. Spiller
Keyword(s):  
Success Probability ◽  
Bell State ◽  
Continuous Variable ◽  
Entanglement Swapping ◽  
Entangled State ◽  
Entanglement Purification ◽  
Hybrid State ◽  
Fock State ◽  
Purification Scheme ◽  
Low Levels

We propose the use of hybrid entanglement in an entanglement swapping protocol, as means of distributing a Bell state with high fidelity to two parties. The hybrid entanglement used in this work is described as a discrete variable (Fock state) and a continuous variable (cat state super- position) entangled state. We model equal and unequal levels of photonic loss between the two propagating continuous variable modes, before detecting these states via a projective vacuum-one-photon measurement, and the other mode via balanced homodyne detection. We investigate homodyne measurement imperfections, and the associated success probability of the measurement schemes chosen in this protocol. We show that our entanglement swapping scheme is resilient to low levels of photonic losses, as well as low levels of averaged unequal losses between the two propagating modes, and show an improvement in this loss resilience over other hybrid entanglement schemes using coherent state superpositions as the propagating modes. Finally, we conclude that our protocol is suitable for potential quantum networking applications which require two nodes to share entanglement separated over a distance of 5 -- 10   km , when used with a suitable entanglement purification scheme.

scholarly journals Entanglement formation in continuous-variable random quantum networks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Bingzhi Zhang ◽  
Quntao Zhuang
Keyword(s):  
Continuous Variable ◽  
Discrete Variable ◽  
Entanglement Dynamics ◽  
Many Body ◽  
Linear Superposition ◽  
Quantum Networks ◽  
Entanglement Generation ◽  
Fundamental Properties ◽  
Many Body Systems ◽  
Nonlinear Nature

AbstractEntanglement is not only important for understanding the fundamental properties of many-body systems, but also the crucial resource enabling quantum advantages in practical information processing tasks. Although previous works on quantum networks focus on discrete-variable systems, light—as the only traveling carrier of quantum information in a network—is bosonic and thus requires a continuous-variable description. We extend the study to continuous-variable quantum networks. By mapping the ensemble-averaged entanglement dynamics on an arbitrary network to a random-walk process on a graph, we are able to exactly solve the entanglement dynamics. We identify squeezing as the source of entanglement generation, which triggers a diffusive spread of entanglement with a "parabolic light cone”. A surprising linear superposition law in the entanglement growth is predicted by the theory and numerically verified, despite the nonlinear nature of the entanglement dynamics. The equilibrium entanglement distribution (Page curves) is exactly solved and has various shapes depending on the average squeezing density and strength.

scholarly journals Complexity Measures for Maxwell–Boltzmann Distribution

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Nicholas Smaal ◽  
José Roberto C. Piqueira
Keyword(s):  
Probability Distributions ◽  
Boltzmann Distribution ◽  
Continuous Variable ◽  
Physical Situation ◽  
Natural Phenomena ◽  
Informational Entropy ◽  
Complexity Measures ◽  
Order And Disorder ◽  
Discrete Probability Distributions ◽  
Common Situation

This work presents a discussion about the application of the Kolmogorov; López-Ruiz, Mancini, and Calbet (LMC); and Shiner, Davison, and Landsberg (SDL) complexity measures to a common situation in physics described by the Maxwell–Boltzmann distribution. The first idea about complexity measure started in computer science and was proposed by Kolmogorov, calculated similarly to the informational entropy. Kolmogorov measure when applied to natural phenomena, presents higher values associated with disorder and lower to order. However, it is considered that high complexity must be associated to intermediate states between order and disorder. Consequently, LMC and SDL measures were defined and used in attempts to model natural phenomena but with the inconvenience of being defined for discrete probability distributions defined over finite intervals. Here, adapting the definitions to a continuous variable, the three measures are applied to the known Maxwell–Boltzmann distribution describing thermal neutron velocity in a power reactor, allowing extension of complexity measures to a continuous physical situation and giving possible discussions about the phenomenon.

CONTINUOUS-VARIABLE QUANTUM TELEPORTATION OF MULTIPARTITE ENTANGLED COHERENT STATES

2011 ◽  
Vol 25 (08) ◽  
pp. 1135-1142 ◽  
Author(s):  
YONG SUN ◽  
BEN-JIN SUN ◽  
MEI-LI SHI ◽  
ZHONG-XIAO MAN ◽  
YUN-JIE XIA
Keyword(s):  
Quantum Teleportation ◽  
Optical Devices ◽  
Continuous Variable ◽  
Phase Shifters ◽  
Entangled State ◽  
Average Fidelity ◽  
Beam Splitters ◽  
Maximal Entanglement ◽  
Entangled Coherent State ◽  
Tripartite Entangled State

We investigate the problem of teleportation of tripartite entangled coherent state (ECS) using linear optical devices such as beam splitters, phase shifters, and two-mode number measurements. The scheme is based on the maximally four-partite ECS with bipartite maximal entanglement as the quantum channel to teleportation tripartite ECS. Our scheme is efficient in the sense that for mean number of photons equal to 2, the minimum of average fidelity (MAF) for teleportation an arbitrary tripartite entangled state is 1-2.3 × 10-7. We also generalize the tripartite scheme into multipartite case and calculate the MAF for the schemes in multipartite cases.

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