Quantum entanglement and classical behaviour

Amit Bhar

Mahmoud Youssef Abd‐Rabbou, Mahmood Shamirzaie, Salman Khan

Abstract This paper investigates the behaviour of the quantum correlations for an accelerated two-qubit system during its interaction with a classical stochastic field, utilizing the Wigner function and concurrence. The non-classical behaviour is indicated by negative values of the Wigner function, while the degree of entanglement is demonstrated by the concurrence. To consider acceleration and interaction with a common or independent environment, we discard the single-mode approximation and utilize the Unruh construction of the quantum field mode in our analysis. Our results suggest that coherence suppression is caused by the acceleration effect, noise strength, and noise frequency. Through an examination of quantum concurrence, this study analyses the level of quantum entanglement that corresponds positively with negative values of the Wigner function. The findings indicate that coherence degradation in the initial system is reduced when observers interact independently with their environments, as opposed to interacting with a common environment. Additionally, the acceleration of both observers has an impact on coherence reduction. During system evolution, the Wigner function displays collapse and reappearance behaviour, while quantum entanglement undergoes local collapse and revival phenomena. Notably, common noise situations exhibit more rapid variation in both the Wigner function and entanglement compared to independent noise configurations.

Manuel Aschwanden

Ying-Yen Liao, Y N Chen, Che‐Ming Li +1 more

A method is proposed to create entanglement between two coupled identical polar molecules separated at a distance of tens of nanometres. Entangled states of two coupled polar molecules controlled by half-cycle pulses are studied theoretically. The von Neumann entropy is calculated to characterize the degree of entanglement. By varying the pulse shape of the applied laser, transition from regular to irregular behaviour occurs. Moreover, the entanglement is also found to be enhanced by applying multiple laser pulses. The behaviour from quantum to classical limit is also discussed.

K. Hess

Jiangfeng Du, Hui Li, Xiaodong Xu +2 more

The discontinuous dependence of the properties of a quantum game on its entanglement has been shown to be very much like phase transitions viewed in the entanglement-payoff diagram (J Du et al 2002 Phys. Rev. Lett. 88 137902). In this paper we investigate such phase-transition-like behaviour of quantum games, by suggesting a method which would help to illuminate the origin of such a kind of behaviour. For the particular case of the generalized Prisoners' Dilemma, we find that, for different settings of the numerical values in the payoff table, even though the classical game behaves the same, the quantum game exhibits different and interesting phase-transition-like behaviour.