On the relation between decoherence and spontaneous symmetry breaking

TL;DR

This paper explores how spontaneous symmetry breaking causes fundamental limits to quantum coherence in many-particle spin qubits, extending previous findings beyond specific models.

Contribution

It introduces a general method to determine decoherence times due to symmetry breaking and applies it to multiple models, linking symmetry breaking to the thin spectrum.

Findings

Decoherence arises from energy shifts in the thin spectrum.

The mechanism is more general than previously shown for the Lieb-Mattis model.

Spontaneous symmetry breaking imposes fundamental limits on quantum coherence.

Abstract

We have recently shown that there is a limit to quantum coherence in many-particle spin qubits due to spontaneous symmetry breaking. These results were derived for the Lieb-Mattis spin model. Here we will show that the underlying mechanism of decoherence in systems with spontaneous symmetry breaking is in fact more general. We present here a generic route to finding the decoherence time associated with spontaneous symmetry breaking in many particle qubits, and subsequently we apply this approach to two model systems, indicating how the continuous symmetries in these models are spontaneously broken and discussing the relation of this symmetry breaking to the thin spectrum. We then present in detail the calculations that lead to the limit to quantum coherence, which is due to energy shifts in the thin spectrum.