Work and information from thermal states after subtraction of energy quanta

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.

Non-Gaussianity of multiple photon-subtracted thermal states in terms of compound-Poisson photon number distribution parameters: theory and experiment

“…Thus, we have shown, how the several measures of non-Gaussianity depend on the parameters of MPSTS: mean photon number µ and coherence parameter a . Here we would like to highlight the kurtosis-based measure, which on the one hand have a simple analytical dependency on µ and a (12), and on the other hand can be directly calculated from the measured quadrature histograms without quantum state reconstruction procedure (14). It has been shown theoretically and validated experimentally that MPSTSs lose their non-Gaussianity during the optical damping.…”

Generation of ideal thermal light in warm atomic vapor

“…The uncertainties of the evaluated entropies have been estimated using the Monte Carlo routine from the uncertainties of the measured numbers of photon clicks. These results qualify the realized single-mode thermal light source for experiments in quantum thermodynamics [18], where the ideal thermal light statistics is required to reliably emulate thermal equilibrium quantum states corresponding to basic energy resources for thermodynamical tests at single photon level [41].…”

Multimode thermal states with multiphoton subtraction: Study of the photon-number distribution in the selected subsystem

“…In Fig.4 (a) we present the distributions P N (14) at m = M . As was shown above, it equals compound Poisson distribution (15), where the mode addition is equivalent to the photon subtraction. In Fig.4 (b) we present the single-mode photon number distributions for m = 1 and M = 1 ÷ 5.…”