Quantum Photovoltaic Cells Driven by Photon Pulses

We investigate the quantum thermodynamics of two quantum systems, a two-level system and a four-level quantum photocell, each driven by photon pulses as a quantum heat engine. We set these systems to be in thermal contact only with a cold reservoir while the heat (energy) source, conventionally given from a hot thermal reservoir, is supplied by a sequence of photon pulses. The dynamics of each system is governed by a coherent interaction due to photon pulses in terms of the Jaynes-Cummings Hamiltonian together with the system-bath interaction described by the Lindblad master equation. We calculate the thermodynamic quantities for the two-level system and the quantum photocell including the change in system energy, the power delivered by photon pulses, the power output to an external load, the heat dissipated to a cold bath, and the entropy production. We thereby demonstrate how a quantum photocell in the cold bath can operate as a continuum quantum heat engine with a sequence of photon pulses continuously applied. We specifically introduce the power efficiency of the quantum photocell in terms of the ratio of output power delivered to an external load with current and voltage to the input power delivered by the photon pulse. Our study indicates a possibility that a quantum system driven by external fields can act as an efficient quantum heat engine under non-equilibrium thermodynamics.

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Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Entropy ◽

10.3390/e23040419 ◽

2021 ◽

Vol 23 (4) ◽

pp. 419

Author(s):

Congzheng Qi ◽

Zemin Ding ◽

Lingen Chen ◽

Yanlin Ge ◽

Huijun Feng

Keyword(s):

Power Output ◽

Performance Optimization ◽

External Load ◽

Thermal Contact ◽

Heat Engine ◽

Design Parameters ◽

Load Effect ◽

Heat Engines ◽

Heat Leakage ◽

Steady Current

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.

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THE ENTANGLED QUANTUM HEAT ENGINE IN THE VARIOUS HEISENBERG MODELS FOR A TWO-QUBIT SYSTEM

International Journal of Quantum Information ◽

10.1142/s0219749913500214 ◽

2013 ◽

Vol 11 (02) ◽

pp. 1350021 ◽

Cited By ~ 5

Author(s):

ERHAN ALBAYRAK

Keyword(s):

Magnetic Field ◽

Constant Magnetic Field ◽

Heat Engine ◽

Exchange Parameter ◽

Thermodynamic Quantities ◽

Two Dimensional ◽

Quantum Heat Engine ◽

Qubit System ◽

Heisenberg Models ◽

Different Temperatures

The four-level entangled quantum heat engine (QHE) is analyzed in the various Heisenberg models for a two-qubit. The QHE is examined for the XX, XXX and XXZ Heisenberg models by introducing a parameter x which controls the strength of the exchange parameter Jz = xJ along the z-axis with respect to the ones along the x- and y-axes, i.e. Jx = Jy = J, respectively. It is assumed that the two-qubit is entangled and in contact with two heat reservoirs at different temperatures and under the effect of a constant magnetic field. The concurrences (C) are used as a measure of entanglement and then the expressions for the amount of heat transferred, the work performed and the efficiency of the QHE are derived. The contour, i.e. the isoline maps, and some two-dimensional plots of the above mentioned thermodynamic quantities are calculated and some interesting features are found.

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A quantum heat engine driven by atomic collisions

Nature Communications ◽

10.1038/s41467-021-22222-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Quentin Bouton ◽

Jens Nettersheim ◽

Sabrina Burgardt ◽

Daniel Adam ◽

Eric Lutz ◽

...

Keyword(s):

Power Output ◽

Quantum Control ◽

High Efficiency ◽

Spin Exchange ◽

Thermal Contact ◽

Heat Engine ◽

Discrete Energy ◽

Large Power ◽

Quantum Heat Engine ◽

Output Fluctuations

AbstractQuantum heat engines are subjected to quantum fluctuations related to their discrete energy spectra. Such fluctuations question the reliable operation of thermal machines in the quantum regime. Here, we realize an endoreversible quantum Otto cycle in the large quasi-spin states of Cesium impurities immersed in an ultracold Rubidium bath. Endoreversible machines are internally reversible and irreversible losses only occur via thermal contact. We employ quantum control to regulate the direction of heat transfer that occurs via inelastic spin-exchange collisions. We further use full-counting statistics of individual atoms to monitor quantized heat exchange between engine and bath at the level of single quanta, and additionally evaluate average and variance of the power output. We optimize the performance as well as the stability of the quantum heat engine, achieving high efficiency, large power output and small power output fluctuations.

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Machine-Learning Assisted Optimisation of Free-Parameters of a Dual-Input Power Amplifier for Wideband Applications

Sensors ◽

10.3390/s21082831 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2831

Author(s):

Teng Wang ◽

Wantao Li ◽

Roberto Quaglia ◽

Pere L. Gilabert

Keyword(s):

Power Amplifier ◽

Power Efficiency ◽

Average Power ◽

Long Term Evolution ◽

Input Power ◽

Global Optimisation ◽

Power Ratio ◽

Term Evolution ◽

Free Parameters

This paper presents an auto-tuning approach for dual-input power amplifiers using a combination of global optimisation search algorithms and adaptive linearisation in the optimisation of a multiple-input power amplifier. The objective is to exploit the extra degrees of freedom provided by dual-input topologies to enhance the power efficiency figures along wide signal bandwidths and high peak-to-average power ratio values, while being compliant with the linearity requirements. By using heuristic search global optimisation algorithms, such as the simulated annealing or the adaptive Lipschitz Optimisation, it is possible to find the best parameter configuration for PA biasing, signal calibration, and digital predistortion linearisation to help mitigating the inherent trade-off between linearity and power efficiency. Experimental results using a load-modulated balanced amplifier as device-under-test showed that after properly tuning the selected free-parameters it was possible to maximise the power efficiency when considering long-term evolution signals with different bandwidths. For example, a carrier aggregated a long-term evolution signal with up to 200 MHz instantaneous bandwidth and a peak-to-average power ratio greater than 10 dB, and was amplified with a mean output power around 33 dBm and 22.2% of mean power efficiency while meeting the in-band (error vector magnitude lower than 1%) and out-of-band (adjacent channel leakage ratio lower than −45 dBc) linearity requirements.

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