Work-minimizing Protocols in Driven-Dissipative Quantum Systems Utilize Impulse Ansatz for Finite-Time Processes

The quest to minimise energy expenditure in driving quantum systems represents a fundamental challenge in physics, with implications for diverse technologies. Masaaki Tokieda from Kyoto University and colleagues now demonstrate a highly effective strategy for achieving this goal, even when systems operate far from equilibrium. The researchers developed a new method to calculate the minimum work needed to manipulate quantum systems interacting with their environment, moving beyond approximations that often fail in realistic scenarios. Their approach reveals that short, sharp impulses remain remarkably effective at minimising energy dissipation, even when the system’s behaviour deviates from simple, predictable patterns, and highlights the limitations of commonly used techniques for optimising these processes. This work establishes a new benchmark for understanding and controlling energy flow in quantum systems, paving the way for more efficient quantum technologies.

Impulse Protocols Minimize Quantum Work Dissipation

The second law of thermodynamics dictates a minimum work requirement for driving a system between thermal equilibrium states, achievable only with infinitely slow processes. Real-world processes occur in finite time, inevitably leading to energy dissipation, motivating the search for optimal control strategies that minimize this loss. This research introduces an impulse-based approach to construct work-minimizing protocols for driven quantum systems interacting with a thermal environment. The method approximates the system’s evolution as a series of instantaneous impulses, allowing scientists to analytically determine the best control parameters.

This approach avoids the computational complexity of solving time-dependent Schrödinger equations, offering an efficient route to identifying protocols that approach the theoretical limit of work expenditure. The resulting protocols demonstrate significant reductions in dissipated work compared to conventional driving schemes, particularly for rapid transitions between equilibrium states. Furthermore, the analysis reveals a fundamental trade-off between process duration and driving field strength, providing insights into the limits of achieving minimal work expenditure in finite-time quantum processes.

Optimal Quantum Control Minimizes Stochastic Work

Scientists developed a numerically exact method to analyze two-level systems interacting with a harmonic oscillator bath, seeking to minimize energy dissipation during finite-time processes. Inspired by optimal solutions for classical systems, the team introduced a novel approach, termed the impulse ansatz, which incorporates the possibility of abrupt changes in driving force. The results demonstrate that impulse-like features remain nearly optimal in the quantum realm, even when the system’s environment exhibits memory effects, particularly at short timescales. This challenges the reliance on approximations that assume instantaneous environmental effects and highlights the importance of fully quantum approaches to optimize finite-time thermodynamic processes, offering a more accurate understanding of energy transfer at the quantum level.

Impulse Control Minimizes Quantum Dissipation

Inspired by optimal solutions for classical systems, the team introduced a novel approach, termed the impulse ansatz, which incorporates the possibility of abrupt changes in driving force. This approach avoids the computational complexity of solving time-dependent Schrödinger equations, offering an efficient route to identifying protocols that approach the theoretical limit of work expenditure. The results demonstrate that impulse-like features remain nearly optimal in the quantum realm, even when the system’s environment exhibits memory effects, particularly at short timescales. This challenges the reliance on approximations that assume instantaneous environmental effects and highlights the importance of fully quantum approaches to optimize finite-time thermodynamic processes, offering a more accurate understanding of energy transfer at the quantum level.