Quantum Otto refrigerators in finite-time cycle period

We derive cooling rate and coefficient of performance as well their variances for a quantum Otto engine proceeding in finite-time cycle period. This machine consists two driven strokes, where the system isolated from heat reservoir undergoes unitary transformation, isochoric steps, system-bath interaction durations take away equilibrium even at respective ends stages. explicitly calculate statistics operating with an analytically solvable two-level system. clarify role four processes on performance. show that there is trade-off between parameter its corresponding variance, thereby indicating or can be enhanced, but cost increasing fluctuations.