False loss of coherence

TL;DR

This paper demonstrates that the loss of coherence in a quantum system's reduced density matrix can lead to mischaracterization of its coherence state, with examples showing systems appearing incoherent while remaining coherent.

Contribution

It reveals that reduced incoherent density matrices do not necessarily indicate true incoherence in quantum systems, challenging common interpretations.

Findings

Reduced density matrices can misrepresent quantum coherence.

Examples include spin boson and harmonic oscillator systems.

Coherence can persist despite apparent incoherence in reduced states.

Abstract

The loss of coherence of a quantum system coupled to a heat bath as expressed by the reduced density matrix is shown to lead to the miss-characterization of some systems as being incoherent when they are not. The spin boson problem and the harmonic oscillator with massive scalar field heat baths are given as examples of reduced incoherent density matrices which nevertheless still represent perfectly coherent systems.