Controlling fluctuations in quantum Otto engines via spin-echo techniques

Fluctuations are an intrinsic feature of quantum thermodynamic processes and can significantly limit the stability and performance of quantum heat engines. In this work, we investigate a coherent-control-based approach to fluctuation suppression in a quantum Otto cycle, employing spin-echo techniques originally developed in the context of dynamical decoupling. Within a generalized two-point measurement framework, we analyze the full counting statistics of work and heat, including higher-order cumulants. We show that appropriately timed spin-echo pulses can substantially suppress fluctuations in both quantities by inducing phase refocusing and reducing trajectory dispersion, while maintaining — and in some regimes slightly enhancing — the average power and efficiency. We emphasize that the introduction of spin-echo control constitutes an additional unitary resource, such that the resulting device should be interpreted as a control-assisted quantum thermal machine rather than a conventional Otto engine. Our analysis focuses on a dissipation-dominated finite-time regime and applies to both transient dynamics and periodic steady states within this framework. Finally, we outline a feasible implementation using trapped-ion platforms, highlighting the experimental accessibility of coherent control strategies for stabilizing quantum thermal machines.