The energetic cost of work extraction by Alexia Auffeves
By ZEEYA MERALI • Dec. 19, 2020 @ 18:14 GMT

We analyze work extraction from a qubit into a wave guide (WG) acting as a battery, where work is the coherent component of the energy radiated by the qubit. The process is stimulated by a wave packet whose mean photon number (the battery's charge) can be adjusted. We show that the extracted work is bounded by the qubit's ergotropy, and that the bound is saturated for a large enough battery's charge. If this charge is small, work can still be extracted. Its amount is controlled by the quantum coherence initially injected in the qubit's state, that appears as a key parameter when energetic resources are limited. This new and autonomous scenario for the study of quantum batteries can be implemented with state-of-the-art artificial qubits coupled to WGs.



Ref: Monsel, Fellous Asiani, Huard, Auffèves, PHYSICAL REVIEW LETTERS 124, 130601 (2020)



Keywords: #quarantinethermo


Thermodynamics beyond the weak coupling limit: energy-temperature uncertainty relation by Janet Anders
By ZEEYA MERALI • Dec. 17, 2020 @ 20:13 GMT

A key assumption in the standard thermodynamic description of macroscopic systems is that the system’s interaction with its environment is very weak and can be neglected. For microscopic systems, however, this assumption breaks down. In this talk I will illustrate the impact of strong coupling between a quantum system and its environment in two instances: i) The modification of a harmonic oscillator's thermal energy when strongly coupled to an environment [1], and ii) the combination of thermal uncertainty with quantum uncertainty in a general energy-temperature thermodynamic uncertainty relation [2]. The energy-temperature uncertainty relation is valid for classical and quantum systems at all coupling strengths. But in the

quantum regime, strong coupling can lead to non-commutativity effects that create coherences even in equilibrium, which increase temperature uncertainty as well as modify a system's heat capacity. The strong coupling corrections are described by the average Wigner-Yanase-Dyson skew information, a quantity connected to measures of coherence.



Keywords: #quarantinethermo


Multi time point (thermodynamic) constraints for periodically driven systems by Raam Uzdin
By ZEEYA MERALI • Dec. 17, 2020 @ 19:56 GMT

Standard thermodynamics deals with initial and final states and not much is known on what happens in between. By extending the notion of passivity to periodically driven systems, we obtain constraints on the dynamics under periodic driving.



Keywords: #quarantinethermo


Quantum Engine Cools and Heats Simultaneously
By ZEEYA MERALI • Dec. 17, 2020 @ 19:07 GMT

FQXi’s Franco Nori and colleagues at RIKEN in Japan have developed a nanodevice that act as a either a heat engine, or a mini-fridge—or, with an added quantum twist— it can both cool and heat at the same time. Their paper was published a paper in Physical Review Letters in October.

You wouldn’t usually want to combine a fridge and a heater—at least not in a macroscale device. But on the nanoscale, such a device might be useful for quickly switching between the two functions, on a quantum computing chip.

In a normal, macroscale fridge, you exchange heat between two baths of fluid: compressing one bath causes it to heat up, while expanding the other makes it cool. In the nano engine, this process is mimicked by increasing or decreasing the gap between internal energy levels in an electron. The team monitored whether the engine was functioning as a heater or a fridge by monitoring microwaves that were emitted by the device. When it functions as both simultaneously, the emitted microwaves combine to create a characteristic interference pattern.


Understanding consciousness within the known laws of physics by Carlo Rovelli
By CARLO ROVELLI • Nov. 16, 2020 @ 07:12 GMT

Abstract: I do not share the feeling that consciousness (whatever this means) cannot be understood in the context of the known physical laws. So far we do not understand it well, but neither do we fully understand thunderstorms, for that matter. I offer three small contributions in the direction of a direct naturalistic account of consciousness: (i) a purely physical account of agency and the openness of the future, which traces the source of information to past low entropy; (ii) a purely physical basis for a simple notion of "meaning"; and (iii) a suggestion that current understanding of quantum matter (without need of panpsychism) weakens the apparent hiatus between the mental and the physical.



Keywords: Mathematical Consciousness Science

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