Abstract
Quantum coherence represented by a superposition of energy eigenstates is, together with energy, an important resource for quantum technology and thermodynamics. Energy and quantum coherence however, can be complementary. The increase of energy can reduce quantum coherence and vice versa. Recently, it was realized that steady-state quantum coherence could be autonomously harnessed from a cold environment. We propose a conditional synthesis of N independent two-level systems (TLS) with partial quantum coherence obtained from an environment to one coherent system using a measurement able to increase both energy and coherence simultaneously. The measurement process acts here as a Maxwell demon synthesizing the coherent energy of individual TLS to one large coherent quantum battery. The measurement process described by POVM elements is diagonal in energy representation and, therefore, it does not project on states with quantum coherence at all. We discuss various strategies and their efficiency to reach large coherent energy of the battery. After numerical optimization and proof-of-principle tests, it opens way to feasible repeat-until-success synthesis of coherent quantum batteries from steady-state autonomous coherence.
Highlights
Quantum thermodynamics is an emerging field[1,2], which combines the principles of two different and very successful fields of physics
Our main focus is on systems with coherent energy, i.e., systems which can appear in a superposition of energy eigenstates being the basic resource of modern quantum physics and, the viable field of research[10,11,12]
Recent literature describes the manipulation of quantum systems, frequently non-interacting TLSs14, or interacting chains of TLSs15, to investigate the effects of the quantum properties of the battery states on the speed of charging and the energy extractability
Summary
Quantum coherence represented by a superposition of energy eigenstates is, together with energy, an important resource for quantum technology and thermodynamics. It has been recently proposed that a residual steady-state coherent energy (energy of the superposition of energy eigenstates) can be autonomously harnessed by elementary TLS from a sufficiently cold environment[13] Stimulated by these results, we consider such an environmentally-induced coherence as a resource to be synthesized. We propose such strategy which is coherently synthesizing excited two-level systems to a larger coherent system with the possibility to enhance both energy and coherence on two and more TLS by the collective quantum measurement with elements diagonal in the energy basis. Such synthesizing unifies the battery build-up and charging process. We emphasize in the region p 1, together with the the fact, that decrease
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