skip to main content

IQIM Postdoctoral and Graduate Student Seminar

Thursday, February 16, 2023
1:00pm to 2:00pm
Add to Cal
Annenberg 121
Ehrenfest's theorem beyond the Ehrenfest time: non-singular classical limit for general open systems
Jess Riedel, NTT Research,

Abstract: In the presence of chaos, wavepackets spread exponentially in time and, when isolated, can form large superpositions in just seconds or minutes even for ordinary macroscopic systems, despite the relative smallness of ħ. Heuristic arguments and examples suggest that decoherence from a weakly coupled environment restores the quantum-classical correspondence, but how weak and under what conditions? We bound the difference between quantum and classical trajectories for general Markovian open systems that holds when the strength of the environment-induced diffusion exceeds a threshold proportional to (ħ/S)^(4/3), where S is the characteristic action of the system. It applies to dynamics generated by arbitrary Hamiltonian and Lindblad operators associated with smooth classical functions H(x,p) and Lk(x,p), and holds for all observables and for times exponentially longer than the Ehrenfest timescale on which the correspondence breaks down in closed systems. Diffusive noise is unavoidable in open systems, but its strength is suppressed by ħ/S, hence vanishing in the classical limit and giving the appearance of reversible dynamics. The 4/3 exponent may be optimal as Toscano et al. have found evidence that the quantum-classical correspondence breaks down in some systems when the diffusion is any weaker.

Attendees joining in person must demonstrate that they comply with Caltech's vaccination requirements (present Caltech ID or AWS ID or vaccination and booster confirmation).

For more information, please contact Marcia Brown by phone at 626-395-4013 or by email at [email protected].