Title: Experimental Determination of Dynamical Lee-Yang Zeros

Abstract:

Statistical physics provides the concepts and methods to explain the phase 
behavior of interacting many-body systems. Investigations of Lee-Yang zeros 
-- complex singularities of the free energy in systems of finite size -- 
have led to a unified understanding of equilibrium phase transitions. 
The ideas of Lee and Yang, however, are not restricted to equilibrium 
phenomena. Recently, Lee-Yang zeros have been used to characterize 
non-equilibrium processes such as dynamical phase transitions in quantum 
systems after a quench or dynamic order-disorder transitions in glasses. 
In this talk, I describe the experimental realization of a scheme to detect 
Lee-Yang zeros in such non-equilibrium settings [1,2]. We extract the 
dynamical Lee-Yang zeros of a stochastic process involving Andreev 
tunneling between a normal-state island and two superconducting leads 
from measurements of the dynamical activity along a trajectory. 
From short-time observations of the Lee-Yang zeros, we predict the 
large-deviation statistics of the dynamical activity which is otherwise 
difficult to measure. Our method paves the way for further experiments 
on the statistical mechanics of many-body systems out of equilibrium.

[1] "Trajectory Phase Transitions, Lee-Yang Zeros, and High-Order Cumulants in Full Counting Statistics", C. Flindt and J. P. Garrahan, Phys. Rev. Lett. 110, 050601 (2013)
[2] "Experimental Determination of Dynamical Lee-Yang Zeros", K. Brandner, V. F. Maisi, J. P. Pekola, J. P. Garrahan, and C. Flindt, Phys. Rev. Lett. 118, 180601 (2017)