We study the dynamics of quantum coherence under Unruh thermal noise and seek under which condition the coherence can be frozen in a relativistic setting. We find that the frozen condition is either (i) the initial state is prepared as an incoherence state or (ii) the detectors have no interaction with the external field. That is to say, the decoherence of the detectors' quantum state is irreversible under the influence of thermal noise induced by Unruh radiation. It is shown that quantum coherence approaches zero only in the limit of an infinite acceleration, while quantum entanglement could reduce to zero for a finite acceleration. It is also demonstrated that the robustness of quantum coherence is better than entanglement under the influence of the atom-field interaction for an extremely large acceleration. Therefore, quantum coherence is more robust than entanglement in an accelerating system and the coherence-type quantum resources are more accessible for relativistic quantum information processing tasks.
The quantum coherence of a multipartite system is investigated when some of the parties are moving with uniform acceleration and the analysis is carried out using the single-mode approximation. Due to acceleration the quantum coherence is divided into two parts as accessible and inaccessible coherence. First we investigate tripartite systems, considering both GHZ and
W states. We find that the quantum coherence of these states does not vanish in the limit of infinite acceleration, rather asymptoting to a nonzero value. These results hold for both single- and two-qubit acceleration. In the GHZ and
W states the coherence is distributed as correlations between the qubits and is known as global coherence. However, quantum coherence can also exist due to the superposition within a qubit, the local coherence. To study the properties of local coherence we investigate a separable state. The GHZ state,
W state, and separable states contain only one type of coherence. Next we consider the
WW and star states in which both local and global coherences coexist. We find that under uniform acceleration both local and global coherence show similar qualitative behavior. Finally, we derive analytic expressions for the quantum coherence of
N-partite GHZ and
W states for
n<N accelerating qubits. We find that the quantum coherence of a multipartite GHZ state falls exponentially with the number of accelerated qubits, whereas for multipartite
W states the quantum coherence decreases only polynomially. We conclude that
W states are more robust to Unruh decoherence and discuss some potential applications in satellite-based quantum communication and black-hole physics.
We studied the quantum correlations of a three-body Unruh–DeWitt detector system using genuine tripartite entanglement (GTE) and geometric quantum discord (GQD). We considered two representative three-body initial entangled states, namely the GHZ state and the W state. We demonstrated that the quantum correlations of the tripartite system are completely destroyed at the limit of infinite acceleration. In particular, it is found that the GQD of the two initial states exhibits “sudden change” behavior with increasing acceleration. It is shown that the quantum correlations of the W state are more sensitive than those of the GHZ state under the effect of Unruh thermal noise. The GQD is a more robust quantum resource than the GTE, and we can achieve robustness in discord-type quantum correlations by selecting the smaller energy gap in the detector. These findings provide guidance for selecting appropriate quantum states and resources for quantum information processing tasks in a relativistic setting.
We consider two entangled accelerating qubits coupled with real scalar fields, each described by the Unruh-Wald model. It is demonstrated that because of the Unruh effect of the fields, the bipartite entanglement between the two qubits suddenly dies when the acceleration of one or more qubits are large enough. We also consider three entangled accelerating qubits in GHZ state and in W state, with equal acceleration-frequency ratio, and found that in either state, the tripartite entanglement suddenly dies at a certain value of acceleration-frequency ratio. The equivalence between the Rindler metric and the Schwarzschild metric in the vicinity of the horizon of a black hole implies that for two entangled qubits outside a black hole, the entanglement suddenly dies when one or both of the qubits are close enough to the horizon, while the three entangled qubits in GHZ or W state, the tripartite entanglement suddenly dies when these qubits are close enough to the horizon.
In this paper, we investigate the influence of the Unruh effect on the achievement of the nonlocal advantage of quantum coherence for a two-qubit system under a relativistic frame. The results show that with the increase of acceleration, it is difficult to realize the nonlocal advantage of quantum coherence and when the acceleration exceeds a certain value, nonlocal advantage of quantum coherence cannot be realized. In addition, we explore the dynamics of Bell nonlocality, steering, quantum coherence, entanglement and quantum discord (QD) under Unruh thermal noise. It is shown that nonlocal advantage of quantum coherence, Bell nonlocality, steering and entanglement experience “sudden death” for a finite acceleration, while quantum coherence and QD vanish only in the limit of an infinite acceleration. We also find that not all nonlocal states can achieve the nonlocal advantage of quantum coherence. It is also demonstrated that the robustness of Bell nonlocality is better than nonlocal advantage of quantum coherence under the influence of the Unruh noise.
Based on Greenberger-Horne-Zeilinger (
GHZ) and
W initial states, the tripartite entanglement of a fermionic system under the amplitude damping channel and in depolarizing noise when two subsystems accelerated is investigated. Unlike the case of two-qubit system in which sudden death occurs easily, we find here that the sudden death never occurs even all subsystems are under the noise environment. We note that both acceleration and environment can destroy the symmetry between the subsystems, but the effect of environment is much stronger than that of acceleration. We also show that an entanglement rebound process will take place when
P>0.75 in the depolarizing noise and the larger acceleration will result in the weaker rebound process.