Decoherence of rotational degrees of freedom

TL;DR

This paper investigates how quantum coherence in rotational degrees of freedom decays due to elastic scattering, revealing temperature-dependent decay rates and comparing them to translational decoherence.

Contribution

It introduces a simple model for rotational decoherence, deriving decay rates for dielectric ellipsoids and mass particles, highlighting differences from translational decoherence.

Findings

Decay rate depends on the difference in scattering amplitudes.

Decay rate for dielectric ellipsoids scales with temperature to the seventh power.

Rotational coherence decays faster than translational coherence in photon scattering environments.

Abstract

The mechanism of decoherence for a quantum system with rotational degrees of freedom is studied. From a simple model of elastic scattering, we show that the non-diagonal density matrix elements of the system exponentially decay. The decay rate depends on the difference of scattering amplitudes for different rotational configurations, leading to the gradual loss of quantum coherence between the pointer states in the system orientational space. For a dielectric ellipsoid immersed in a photon-gas environment (assuming no absorption), the decay rate is found to be proportional to the seventh power of the temperature. For an ellipsoidal object interacting with mass particles, the decay rate is proportional to the 5/2 power of the temperature. Both are different from the case of translational decoherence induced by the same environment scattering. For photon scattering, the coherence time in the rotational degrees of freedom is shown to be much shorter than that in the translational degrees of freedom.