Landauer's principle in qubit-cavity quantum-field-theory interaction in vacuum and thermal states

Abstract

We consider quantum decoherence and Landauer's principle in qubit-cavity quantum field theory (QFT) interaction, treating the qubit as the system and cavity QFT as the environment. In particular, we investigate the changes that occur in the system with a pure initial state and environment during the decoherence process, with or without energy dissipation, and compare the results with the case in which the initial state of the system is a mixed state and thus decoherence is absent. When we choose an interaction Hamiltonian such that the energy and coherence of the system change simultaneously, the population change of the system and the energy change are the same when the initial state is mixed. However, the decoherence terms increase the von Neumann entropy of the system. On the other hand, if the interaction Hamiltonian does not change the energy of the system, there is only the decoherence effect. The environment will be a distribution in the basis of the displaced number state and always increases the energy. Landauer's principle is satisfied in both cases.

Landauer's princple for Fermionic field in one dimensional bag

“…When the initial state of the Dirac field is a thermal state, we obtained the heat transfer and entropy grow approximately under some additional conditions and also verified the validity of the Landauer's principle. We find that compared to the case of real scalar field [20], the results of vacuum initial state differs only due to the helicity of the Dirac field while for thermal initial state, the distinguishability of fermion and anti-fermion also plays its part. Our work holds the potential of being extended to the QCD systems and neucleaon-neutrino systems [26,27,28], which may be experimental feasible.…”

“…Taking TR → 0, the results reduce to (15) under resonance approximation. Substitute (20) into (21) it is easy to check that the Landauer's principle ∆Q ≥ TR∆S is satisfied. The initial state of the detector can also be assigned with a temperature TD with p = e .…”

“…We obtain the heat transfer and entropy change are obtained in two cases, one is the Dirac field is prepared initially in vacuum state while another is the thermal initial state with long interaction period and the detector is in resonance with one of the field model. By comparing with real scalar field [20], we find that for vacuum initial state, the heat transfer and entropy grow are modified only due to the helicity of the fermion and anti-fermion. While for thermal initial state, the results are modified also from the distinguishability of the fermion and anti-fermion.…”

“…The discussion on the implication of Landauer's principle on quantum field theory is a newly emerged topic. In [20,21], the authors discussed the Landauer's principle of an Unruh-DeWitt detector coupled to real scalar field through monopole momentum. In quantum theory, the field can be classified into two kinds: fermionic ones and bosonics ones, and they behaves very differently from each other.…”

Decoherence and thermalization of Unruh-DeWitt detector in arbitrary dimensions

“…Recently it was found that the decoherence rate can be used to measure the Unruh effect [38]. We can also study the exchange of energy and information during the interaction between the detector and quantum field theory [39][40][41], which may help us to understand the feedback and back-reaction obtained from the measurements, as well as the connection between gravity and quantum theory. In [40] we also investigated the decoherence of the qubit coupled to a thermal quantum field theory in a cavity, and the results are also consistent with our Theorem 1.…”