Demonstration of Jarzynskis Equality in Open Quantum Systems Using a Step-Wise Pulling Protocol

We present a generalization of Jarzynski’s Equality, applicable to quantum systems, relating discretized mechanical work and free-energy changes. The theory is based on a step-wise pulling protocol. We find that work distribution functions can be constructed from fluctuations of a reaction coordinate along a reaction pathway in the step-wise pulling protocol. We also propose two sets of equations to determine the two possible optimal pathways that provide the most significant contributions to free-energy changes. We find that the transitions along these most optimal pathways, satisfying both sets of equations, follow the principle of detailed balance. We then test the theory by explicitly computing the free-energy changes for a one-dimensional quantum harmonic oscillator. This approach suggests a feasible way of measuring the fluctuations to experimentally test Jarzynski’s Equality in many-body systems, such as Bose-Einstein condensates.

💡 Research Summary

The paper presents a rigorous extension of Jarzynski’s Equality (JE) to open quantum systems by introducing a step‑wise pulling protocol. Traditional JE relates the exponential average of work, ⟨e^{−βW}⟩, to the free‑energy difference ΔF for closed systems, where work is simply the difference between final and initial energy eigenvalues. In open quantum systems coupled to a thermal bath, this definition fails because the system exchanges heat with the environment. While Crooks and Campisi have generalized JE for classical stochastic and strongly coupled quantum systems, they have not demonstrated that the discretized mechanical work W = ∑