Irreversible work and internal friction in a quantum Otto cycle of a single arbitrary spin

Abstract

We propose an arbitrary driven spin as the working fluid of a quantum Otto cycle in the presence of internal friction. The role of total allocated time to the adiabatic branches of the cycle, generated by different control field profiles, on the extractable work and the thermal efficiency are analyzed in detail. The internal friction is characterized by the excess entropy production and quantitatively determined by studying the closeness of an actual unitary process to an infinitely long one via quantum relative entropy. It is found that the non-ideal, finite-time adiabatic transformations negatively effect the work output and the thermal efficiency of the quantum heat engine. The nonmonotone dependence of the work output, thermal efficiency, entropy production and the internal friction on the total adiabatic time are elucidated. It is also found that almost frictionless adiabatic transformations with small entropy production can be obtained in a short adiabatic time.

Spin quantum heat engines with shortcuts to adiabaticity

“…1 (a) that the efficiency of the STA engine has a finite value close to the adiabatic engine at very short driving times while the non-adiabatic engine is unable to generate work output. This efficiency lag until τ ≈ 19.5 in the case of non-adiabatic engine is due to the irreversible entropy production when the working fluid experiences a fast driving during the work strokes [22,36,71,72,77]. The STA technique we employ for our engine, suppresses such unwanted irreversible entropy production at the cost of implementing the external CD Hamiltonian, which is responsible for the deviation of the STA engine efficiency from the adiabatic one at short times.…”

“…Despite their limited practical value, QHEs are pivotal to reveal fundamental limits on the operation of quantum machines from a thermodynamical perspective. Accordingly, many proposals to realize them can be found in the literature [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], some of which take into account finite-time engine cycles [22][23][24][25][26]. In addition, the effects of the profound quantum nature of the QHE such as such as cooperativity [27][28][29][30][31], coherence and correlations [32][33][34] on the performance of QHEs have also been investigated.…”

Algorithmic quantum heat engines

“…Even if we increase the work output iterating more PPA, we may lose power output. For a quantum Otto cycle using NMR system as working fluid, the adiabatic stages of the cycle are considered as fast compared to the isochoric stages [31]. We estimate the power output of cycles considering isochoric stages and HBAC.…”

“…One can use non-classical resources, though such a resource would not be natural and require some generation cost reducing overall efficiency. Alternatively one can use dynamical shortcuts to speeding up adiabatic transformations [31] but this would increase experimental complexity, and moreover in NMR thermalization is more seriously slow step reducing the power output of the NMR machines.…”

Critical-point behavior of a measurement-based quantum heat engine

“…So, during this stage, no heat is exchanged, and the change in entropy is zero. This refers to a reversible adiabatic process (isentropic process), that is associated with no internal friction or heat leak [38][39][40][41]. Moreover, such heat leaks would have appeared in presence of inhomogeneous magnetic field [40], which is not the case in the present model.…”