Quantum Measurement Cooling

Buffoni, Lorenzo; Solfanelli, Andrea; Verrucchi, Paola; Cuccoli, Alessandro; Campisi, Michele

doi:10.1103/physrevlett.122.070603

Cited by 153 publications

(118 citation statements)

References 33 publications

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“…(for α=H, C). If we also require that Γ(ò)=Γ(−ò), which physically means that the rates do not distinguish which one of the two energy levels is the ground and excited state, we find that equation (5) can be simplified to…”

Section: Appendix B Maximum Power Formula and Finite-time Correctionsmentioning

confidence: 99%

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

et al. 2019

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We study how to achieve the ultimate power in the simplest, yet non-trivial, model of a thermal machine, namely a two-level quantum system coupled to two thermal baths. Without making any prior assumption on the protocol, via optimal control we show that, regardless of the microscopic details and of the operating mode of the thermal machine, the maximum power is universally achieved by a fast Otto-cycle like structure in which the controls are rapidly switched between two extremal values. A closed formula for the maximum power is derived, and finite-speed effects are discussed. We also analyze the associated efficiency at maximum power showing that, contrary to universal results derived in the slow-driving regime, it can approach Carnot's efficiency, no other universal bounds being allowed.'fast-driving' regime, i.e. when the driving frequency is faster than the typical dissipation rate induced by the baths, which has received little attention in literature [50][51][52].By applying our optimal protocol to heat engines and refrigerators, we find new theoretical bounds on the efficiency at maximum power (EMP). Many upper limits to the EMP, strictly smaller than Carnot's efficiency, have been derived in literature, such as the Curzon-Ahlborn and Schmiedl-Seifert efficiencies. The Curzon-Ahlborn efficiency emerges in various specific models [53][54][55], and it has been derived by general arguments from linear irreversible thermodynamics [56]. The Schmiedl-Seifert efficiency has been proven to be universal in cyclic Brownian heat engines [57] and for any driven system operating in the slow-driving regime [24]. By studying the efficiency of our system at the ultimate power, i.e. in the fast-driving regime, we prove that there is no fundamental upper bound to the EMP. Indeed, we show that the Carnot efficiency is reachable at maximum power through a suitable engineering of the bath couplings. This is our second main results, illustrated in figures 2(b), (c) and figure 3. In view of experimental implementations, we assess the impact of finite-time effects on our optimal protocol, finding that the maximum power does not decrease much if the external driving is not much slower than the typical dissipation rate induced by the baths [58,59]. Furthermore, we apply our optimal protocol to two experimentally accessible models, namely photonic baths coupled to a qubit [22, 60-63] and electronic leads coupled to a quantum dot [21,23,58,59,64,65].C , and Γ in (c) denotes *  G( ) H . 4 In principle, one can consider a broader family of controls including the possibility of rotating the Hamiltonian eigenvectors; however there is evidence that such an additional freedom does not help in two-level systems [45, 46]. ≔ [ ] ( ) J J t p t J J t p t

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Section: Appendix B Maximum Power Formula and Finite-time Correctionsmentioning

confidence: 99%

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

et al. 2019

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“…This might explain the plethora of studies to investigate possible enhancements of engine performance through the exploitation of quantum resources including coherence [8][9][10][11][12][13][14][15], measurement effects [16], squeezed reservoirs [17][18][19], quantum phase transitions [20], and quantum many-body effects [15,[21][22][23]. Other works have examined the fundamental differences between quantum and classical thermal machines [24][25][26], finite time cycles [13,27,28], utilizing shortcuts to adiabaticity [12,22,23,[29][30][31][32][33], operating over non-thermal states [34,35], non-Markovian effects [36], magnetic systems [37][38][39][40][41][42], anharmonic potentials [43], optomechanical implementation [44], quantum dot implementation [38,40,42], implementation in 2D materials…”

Section: Introductionmentioning

confidence: 99%

Bosons outperform fermions: The thermodynamic advantage of symmetry

Myers

Deffner

2020

Phys. Rev. E

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We examine a quantum Otto engine with a harmonic working medium consisting of two particles to explore the use of wave function symmetry as an accessible resource. It is shown that the bosonic system displays enhanced performance when compared to two independent single particle engines, while the fermionic system displays reduced performance. To this end, we explore the trade-off between efficiency and power output and the parameter regimes under which the system functions as engine, refrigerator, or heater. Remarkably, the bosonic system operates under a wider parameter space both when operating as an engine and as a refrigerator.

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“…Depending on the sign of Q h , Q c and W, TTMs may depict four distinct regimes of operation [53,54],…”

Section: Thermalization Stroke ( T )mentioning

confidence: 99%

Quantum magnetometry using two-stroke thermal machines

et al. 2020

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The precise estimation of small parameters is a challenging problem in quantum metrology. Here, we introduce a protocol for accurately measuring weak magnetic fields using a two-level magnetometer, which is coupled to two (hot and cold) thermal baths and operated as a two-stroke quantum thermal machine. Its working substance consists of a two-level system (TLS), generated by an unknown weak magnetic field acting on a qubit, and a second TLS arising due to the application of a known strong and tunable field on another qubit. Depending on this field, the machine may either act as an engine or a refrigerator. Under feasible conditions, determining this transition point allows to reduce the relative error of the measurement of the weak unknown magnetic field by the ratio of the temperatures of the colder bath to the hotter bath.

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Quantum Measurement Cooling

Cited by 153 publications

References 33 publications

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

Bosons outperform fermions: The thermodynamic advantage of symmetry

Quantum magnetometry using two-stroke thermal machines

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