Prof. Tapio Ala-Nissilä (Aalto University, Finland, and Loughborough University, UK)
Definition and measurement of work done on a driven quantum system remains a major challenge in quantum thermodynamics. For closed systems, the standard way to define work is to consider the two-measurement protocol (TMP), where the system is measured at the beginning and end of the drive leading to wave function collapse (loss of quantum coherence) to an energy eigenstate. For open systems, the stochastic mapping to the Lindblad master equation and its unraveling by quantum jumps offers a powerful way to define and calculate thermodynamics of work and the related fluctuation relations within the TMP . However, for quantum systems with coherence it has recently been shown that it is impossible to define a work operator that satisfies proper physical requirements (the "no-go" theorem) . To this end, we propose a novel way to define work based on the Hamilton-Jacobi formulation of quantum mechanics, which allows to define phase space trajectories with well-defined energy for any wave function . We illustrate this approach by explicit calculations for a driven quantum harmonic oscillator. 1. S. Suomela, J. Salmilehto, I.G. Savenko, T. Ala-Nissila, and M. Mottonen, Phys. Rev. E 91, 022126 (2016). 2. M. Perarnau-Llobet, E. Baumer, K.V. Hovhannisyan, M. Huber, and A. Acin, Phys. Rev. Lett. 118, 070601 (2017). 3. R. Sampaio, S. Suomela, T. Ala-Nissila, J. Anders, and Th. Philbin, https://arxiv.org/abs/1707.06159(2017).