Abstract
We study the influence of the thermal background on the existence of the anti-Unruh effect. For the massless scalar field, we present that the anti-Unruh effect can appear when the detector is accelerated in the thermal field, which is shown to be absent when accelerating in the Minkowski vacuum. For the massive scalar field, it is found that the anti-Unruh effect which exists in the case for accelerated detectors in the vacuum can disappear when the background temperature increases. We use the many-body entangled quantum state to study the situation of the massive scalar field. When the many-body state is accelerated, its entanglement is decreasing with the increase of the background temperature and the phenomenon of the sudden death for entanglement occurs. This provides a valuable indication that the anti-Unruh effect can exist below some specific background temperature, dependent on the actual experimental environment.
Highlights
The Unruh effect [1] was discovered in 1976, which states that an observer with uniform acceleration would feel a thermal bath of particles in the Minkowski vacuum of a free quantum field
In the second section we review the two-level Unruh-DeWitt (UDW) detector model, and investigate whether the anti-Unruh effect appears for the environment of the vacuum or the thermal field with the condition of the massless scalar field
This is just the result in Ref. [21] that the anti-Unruh effect is absent for accelerated detectors in the Minkowski vacuum of a massless scalar field
Summary
The Unruh effect [1] was discovered in 1976, which states that an observer with uniform acceleration would feel a thermal bath of particles in the Minkowski vacuum of a free quantum field. Whether the earlier investigation of the anti-Unruh effect for accelerated many-body quantum systems in vacuum is still hold in the thermal background is unclear both in mathematical and physical perspective. This constitutes the main motivation for the present work. We investigate the influence of background thermal field on the existence of anti-Unruh effect, and we will study the influence on the accelerated many-body quantum systems. The model for the atom accelerated in the thermal field is given in the third section This is followed in the fourth section by the discussions on the influence of acceleration on entanglement for TF states in the thermal background, where the spin squeezing parameter is used to measure the change of entanglement.
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