Spin quantum heat engines with shortcuts to adiabaticity

Abstract

We consider a finite-time quantum Otto cycle with single and two-spin-1/2 systems as its working medium. In order to mimic adiabatic dynamics at a finite time, we employ a shortcut-to-adiabaticity technique and evaluate the performance of the engine including the cost of the shortcut. We compare our results with the true adiabatic and non-adiabatic performances of the same cycle. Our findings indicate that the use of the shortcutto-adiabaticity scheme significantly enhances the performance of the quantum Otto engine as compared to its adiabatic and non-adiabatic counterparts for different figures of merit. *

Energetic cost of quantum control protocols

“…Our aim is to both qualitatively and quantitatively assess the cost of implementing these protocols, which is a topic that has ignited significant interest recently [5,[8][9][10][11][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Indeed as discussed in [2] the notion of the cost has been somewhat loosely employed and therefore different quantifiers probe different aspects of the systemʼs energy or its interactions.…”

“…Firstly, as we shall focus on unitary dynamics, any additional energy resources employed are not dissipated. This is a subtle issue that is particularly relevant if one wishes to extend our analysis to the performance of thermodynamic cycles [8][9][10][11][12], as it is possible for the additional energy requirements invested in achieving coherent control to be recycled, see e.g. [20,21].…”

“…While such an omission is evidently justified when one is solely interested in studying a particular quantum phenomenon, it is vital to account for such expenditures when developing novel technologies that exploit these quantum features. Indeed, recently the application of control techniques that can achieve an effective adiabatic dynamics in a finite time, called 'shortcuts-to-adiabaticity' [1,2], has been shown to be highly effective in a diverse range of settings including quantum gates [5], quantum games [6,7] nano-scale thermodynamic cycles [8][9][10][11][12], open quantum systems [13][14][15][16], manipulating critical many-body systems [17,18], and quantum precision measurements [19]. This further highlights the importance of understanding the additional resources required to achieve precise control in a quantitative manner.…”

“…The question of how to quantify the necessary resources to control a quantum system using a particular protocol has recently become a topic of intense research activity (indeed, in the context of thermodynamic cycles the issue becomes more subtle since any additional energy which is not dissipated can in principle be recycled and act as a catalyst [20]). The variety of ways in which a particular set-up can be coherently controlled has led to a plethora of definitions [5,[8][9][10][11][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Nevertheless, since many of these quantifiers invariably share some common traits, it leads to a natural question: which control protocols are the most resource intensive?…”

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

“…Quantum thermodynamics [6][7][8] has emerged both as a field of fundamental interest, and as a potential candidate to improve the performance of thermal machines [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The optimal performance of these systems has been discussed within several frameworks and operational assumptions, ranging from low-dissipation and slow driving regimes [24][25][26][27][28], to shortcuts to adiabaticity approaches [29][30][31][32], to endoreversible engines [33,34]. Several techniques have been developed for the optimal control of two-level systems for achieving a variety of goals: from optimizing the speed [35][36][37], to generating efficient quantum gates [38,39], to controlling dissipation [40,41], and to optimizing thermodynamic performances [42][43][44][45][46][47].…”