Passivity Deformation Approach for the Thermodynamics of Isolated Quantum Setups

Recently implemented quantum devices such as quantum processors and quantum simulators combine highly complicated quantum dynamics with high-resolution measurements. We present a passivity deformation methodology that sets constraints on the evolution of such quantum devices. The approach yields bounds that are often tighter, and thus more predictive, than the quantum microscopic analogue of the second law of thermodynamics. In particular, (i) it yields tight bounds even when the environment is microscopic; (ii) it successfully handles the ultracold limit; (iii) it enables one to account for constrained dynamics; and (iv) it bounds observables that do not appear in the second law of thermodynamics. Furthermore, this framework provides insights into nonthermal environments, correlated environments, coarse graining in microscopic setups, and the ability to detect heat leaks. Our findings can be explored and used in physical setups such as trapped ions, superconducting circuits, neutral atoms in optical lattices, and more.

Automated summary

This study introduces a passivity deformation methodology for constraining the evolution of quantum devices, resulting in tighter bounds for quantum dynamics. The approach is applicable to microscopic environments and successfully handles the ultracold limit, constrained dynamics, and observable constraints not covered by the second law of thermodynamics.