Work and information from thermal states after subtraction of energy quanta

TL;DR

This paper demonstrates a method to conditionally prepare out-of-equilibrium quantum states of a thermal oscillator, enabling higher work extraction and information transmission than traditional cooling or heating, with implications for quantum thermodynamics.

Contribution

It introduces and experimentally verifies a novel conditional state preparation technique that enhances work and information transfer in quantum thermodynamics.

Findings

Conditional energy subtraction increases available work and information.

Average energy of the oscillator can grow despite energy subtraction.

The approach outperforms traditional cooling or heating in certain quantum tasks.

Abstract

Quantum oscillators prepared out of thermal equilibrium can be used to produce work and transmit information. By intensive cooling of a single oscillator, its thermal energy deterministically dissipates to a colder environment, and the oscillator substantially reduces its entropy. This out-of-equilibrium state allows us to obtain work and to carry information. Here, we propose and experimentally demonstrate an advanced approach, conditionally preparing more efficient out-of-equilibrium states only by a weak dissipation, an inefficient quantum measurement of the dissipated thermal energy, and subsequent triggering of that states. Although it conditionally subtracts the energy quanta from the oscillator, average energy grows, and second-order correlation function approaches unity as by coherent external driving. On the other hand, the Fano factor remains constant and the entropy of the subtracted state increases, which raise doubts about a possible application of this approach. To resolve it, we predict and experimentally verify that both available work and transmitted information can be conditionally higher in this case than by arbitrary cooling or adequate thermal heating up to the same average energy. It qualifies the conditional procedure as a useful source for experiments in quantum information and thermodynamics.