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arXiv · 1807.03467

Spatially Overlapped Partners in Quantum Field Theory

Jose Trevison·Koji Yamaguchi·Masahiro Hotta
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Abstract

In quantum field theory particles are physically defined as what Unruh-DeWitt particle detectors observe. By detecting a particle mode $A$, a reduced density operator for a quantum state of $A$ is constructed. Even if the entire quantum state of the quantum field is pure, the state of $A$ is not pure but mixed due to entanglement between other subsystems. The partner mode $B$ of the field is defined as a purification partner of $A$ such that the $AB$ system in a pure state. We show that, without any fine-tuning of the particle detector design of $A$, the weighting function of partner $B$ has spatial overlap of that of $A$. We show a general formula of partner $B$ associated with arbitrarily fixed $A$ of a free field in a general Gaussian state. We demonstrate an example of memory effects in an expanding Freedman-Roberson-Walker universe.

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Jose Trevison, Koji Yamaguchi, Masahiro Hotta. 2018-07-10. Spatially Overlapped Partners in Quantum Field Theory. https://doi.org/10.1088/1751-8121/ab065b

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