# Q+ hangout with Jonathan Oppenheim

We'd like to announce the next Q+ hangout:

Date: 24th April 2012

Time: 14:00 British Summer Time

Title: Fundamental limitations for quantum and nano thermodynamics

Speaker: Jonathan Oppenheim (University College London)

Abstract:

The relationship between thermodynamics and statistical physics is valid in the thermodynamic limit -- when the number of particles involved becomes very large. Here we study thermodynamics in the opposite regime -- at both the nano scale, and when quantum effects become important. Applying results from quantum information theory we construct a theory of thermodynamics in these extreme limits. In the quantum regime, we find that the standard free energy no longer determines the amount of work which can be extracted from a resource, nor which state transitions can occur spontaneously. We derive a criteria for thermodynamical state transitions, and find two free energies: one which determines the amount of work which can be extracted from a small system in contact with a heat bath, and the other which quantifies the reverse process. They imply that generically, there are additional constraints which govern spontaneous thermodynamical processes. We find that there are fundamental limitations on work extraction from nonequilibrium states, due to both finite size effects which are present at the nano scale, as well as quantum coherences. This implies that thermodynamical transitions are generically irreversible at this scale, and we quantify the degree to which this is so, and the condition for reversibility to hold. There are particular equilibrium processes which approach the ideal efficiency, provided that certain special conditions are met.

Based on http://arxiv.org/abs/1111.3834

Biography: Jonathan Oppenheim has recently moved to University College London. He is an expert in quantum information theory and quantum gravity. His Ph.D. under Bill Unruh at the University of British Columbia was on Quantum time. In 2004 he was a postdoctoral researcher under Jacob Bekenstein and then held a University Research Fellowship at Cambridge University. Together with MichaĆ Horodecki and Andreas Winter, he discovered quantum state-merging and used this primitive to show that quantum information could be negative.