Optimal work extraction from quantum states by photo-assisted Cooper pair tunneling

Abstract

The theory of quantum thermodynamics predicts fundamental bounds on work extraction from quantum states. As these bounds are derived in a very general and abstract setting, it is unclear how relevant they are in an experimental context, where control is typically limited. Here we address this question by showing that optimal work extraction is possible for a realistic engine. The latter consists of a superconducting circuit, where a LC-resonator is coupled to a Josephson junction. The oscillator state fuels the engine, providing energy absorbed by Cooper pairs, thus producing work in the form of an electrical current against an external voltage bias. We show that this machine can extract the maximal amount of work from all Gaussian and Fock states. Furthermore, we consider work extraction from a continuously stabilized oscillator state. In both scenarios, coherence between energy eigenstates is beneficial, increasing the power output of the machine. This is possible because the phase difference across the Josephson junction provides a phase reference.

Extractable Work, the Role of Correlations, and Asymptotic Freedom in Quantum Batteries

“…0 π/2 π 3π/2 2π √ N gτ between the mean energy E(ρ) = tr[Hρ] of the state ρ andthat, E(ρ) = tr[Hρ], of the passive counterpartρ of ρ [24][25][26][27][28][29][30]. The latter is defined as the density matrix of X which is diagonal on the eigenbasis of H and whose eigenvalues correspond to a proper reordering of those of ρ, i.e.ρ = n r n | n n | with ρ = n r n |r n r n |, H = n n | n n |, with r 0 ≥ r 1 ≥ · · · and 0 ≤ 1 ≤ · · · , yielding E(ρ) = n r n n .…”

Fundamental limitations on photoisomerization from thermodynamic resource theories

“…This work leverages resource theories, which have remained largely abstract, to solve known problems in experimental systems. A bridge for thermodynamic resource theories from mathematical physics to the real physical world was called for recently [121]; construction has just begun [72,[122][123][124]. Experimental proposals designed to realize resource-theory results have provided a valuable first step.…”

Physical Implementations of Quantum Absorption Refrigerators

“…The ability to tune the desired terms into resonance using externally controlled parameters, such as a voltage and a magnetic field, make this system a promising candidate for implementing different types of thermal machines. In addition to the absorption refrigerator, a heat engine [51], a thermometer [10], as well as a machine that extracts work from quantum states [73] were investigated.…”