Cyril Elouard

The role of quantum measurement in stochastic thermodynamics

This article sets up a new formalism to investigate stochastic thermodynamics in the quantum regime, where stochasticity and irreversibility primarily come from quantum measurement. In the absence of any bath, we define a purely quantum component to heat exchange, that corresponds to energy fluctuations caused by quantum measurement. Energetic and entropic signatures of measurement-induced irreversibility are then explored for canonical experiments of quantum optics, and the energetic cost of counter-acting decoherence is studied on a simple state-stabilizing protocol. By placing quantum measurement in a central position, our formalism contributes to bridge a gap between experimental quantum optics and quantum thermodynamics, and opens new paths to characterize the energetic features of quantum processing.Rebuilding quantum thermodynamics on quantum measurementMeasuring a quantum system is an ultimately random operation. It induces a genuinely quantum time arrow, increasing the system’s entropy. But because it perturbs its state, quantum measurement also provides energy to the quantum system. These energetic quantum fluctuations play the same role as thermal fluctuations in thermodynamics, while being of quantum nature. Building on such “Quantum Heat”, a group of scientists from france provided a thermodynamic analyzis of canonical experiments of quantum optics. They show that quantum heat is a major concept to evaluate the performances of a basic protocol to counteract the decoherence of a quantum bit. The findings pave the way towards a new generation of quantum engines, powered by quantum measurement. They bring new tools to investigate the energetic cost of quantum protocols performed at ultra-low temperature, in the presence of decoherence.

Extracting Work from Quantum Measurement in Maxwell’s Demon Engines

The essence of both classical and quantum engines is to extract useful energy (work) from stochastic energy sources, e.g., thermal baths. In Maxwells demon engines, work extraction is assisted by a feedback control based on measurements performed by a demon, whose memory is erased at some nonzero energy cost. Here we propose a new type of quantum Maxwells demon engine where work is directly extracted from the measurement channel, such that no heat bath is required. We show that in the Zeno regime of frequent measurements, memory erasure costs eventually vanish. Our findings provide a new paradigm to analyze quantum heat engines and work extraction in the quantum world.

Probing quantum fluctuation theorems in engineered reservoirs

Fluctuation Theorems are central in stochastic thermodynamics, as they allow for quantifying the irreversibility of single trajectories. Although they have been experimentally checked in the classical regime, a practical demonstration in the framework of quantum open systems is still to come. Here we propose a realistic platform to probe fluctuation theorems in the quantum regime. It is based on an effective two-level system coupled to an engineered reservoir, that enables the detection of the photons emitted and absorbed by the system. When the system is coherently driven, a measurable quantum component in the entropy production is evidenced. We quantify the error due to photon detection inefficiency, and show that the missing information can be efficiently corrected, based solely on the detected events. Our findings provide new insights into how the quantum character of a physical system impacts its thermodynamic evolution.

Extracting Work from Quantum Measurement in Maxwell Demon Engines

We propose a new type of Maxwell demon engine where the work is directly extracted from the measurement channel, requiring no heat bath. In the regime of frequent measurements, memory erasure costs eventually vanish.

Reversible information-to-energy conversions in a quantum hybrid system

We investigate the properties of a quantum hybrid opto-mechanical transducer in the context of information thermodynamics, and show that it provides a valuable platform to monitor information- to-energy conversions at the single bit level.