Experimental observation of Loschmidt time reversal of a Quantum Chaotic System

TL;DR

This paper reports an experiment demonstrating approximate time reversal of chaotic quantum evolution in ultra cold atoms, showing that initial states can be reconstructed after chaotic dynamics, with a resulting narrowing of momentum distribution.

Contribution

It presents the first experimental observation of Loschmidt time reversal in a quantum chaotic system using Bose-Einstein condensates and a delta-kicked rotor setup.

Findings

Initial quantum states can be approximately reconstructed after chaotic evolution.

The momentum distribution narrows after the time reversal sequence.

The mechanism works within a narrow momentum range.

Abstract

We have performed an experiment to demonstrate the approximate time reversal of a "chaotic" time evolution of atomic deBroglie waves. We use ultra cold atoms from a Bose-Einstein condensate in a quantum $\delta$-kicked rotor experiment, and show that an initial state can be approximately re-created even after a period of "chaotic" evolution (a number of kicks). As this mechanism only works for a very narrow range of momenta, the net effect is a narrowing of the momentum distribution after the kick sequence.