https://doi.org/10.1140/epjc/s10052-017-5145-6
Regular Article - Theoretical Physics
Decoherence and disentanglement of qubits detecting scalar fields in an expanded spacetime
1
Department of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai, 200433, China
2
Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai, 200433, China
* e-mail: yushi@fudan.edu.cn
Received:
15
December
2016
Accepted:
19
August
2017
Published online:
9
September
2017
We consider Unruh–Wald qubit detector model adopted for the far future region of an exactly solvable 
dimensional scalar field theory in a toy model of Robertson–Walker expanding spacetime. It is shown that the expansion of the spacetime in its history enhances the decoherence of the qubit coupled with a scalar field. Moreover, we consider two entangled qubits, each locally coupled with a scalar field. The expansion of the spacetime in its history degrades the entanglement between the qubits, and it can lead to entanglement’s sudden death if the initial entanglement is small enough. The details depend on the parameters characterizing the expansion of the spacetime. This work, on a toy model, suggests that the history of the spacetime might be probed through the coherent and entanglement behavior of the future detectors of quantum fields. In the present toy model, the two cosmological parameters can be determined from the quantum informational quantities of the detectors.
© The Author(s), 2017
