Fig. 8
From: Quantum engine efficiency bound beyond the second law of thermodynamics
Efficiency bounds for the Otto-like cycle. Actual efficiency η and alternative efficiency bounds (the explicit expressions are summarised in Methods ‘Expressions used in Fig. 8’) for an Otto-like cycle implemented with a harmonic-oscillator working medium and a squeezed thermal bath as a function of a the frequency ratio and b the squeezing parameter. The bounds only hold in the regime \({\cal E}_{{\mathrm{d,c}}} \le 0\) (see text). Parameters: Th = 3Tc and a squeezing parameter r = 0.5 and b oscillator frequencies ωc/ωh = 0.5
