Low-temperature coherence properties of Z_2 quantum memory

TL;DR

This paper studies the low-temperature coherence properties of Z_2 quantum memory, revealing superpositions of macroscopically distinct states and limitations on coherence power, with implications for quantum information storage.

Contribution

It demonstrates the existence of superpositions in Z_2 quantum memory at low temperatures and discusses the limitations and improvements related to this memory type.

Findings

Memory exhibits superposition of macroscopically distinct states at low temperature

Coherence power is limited by space and time constraints

Discussion of RVB memory as an improvement

Abstract

We investigate low-temperature coherence properties of the Z_2 quantum memory which is capable of storing the information of a single logical qubit. We show that the memory has superposition of macroscopically distinct states for some values of a control parameter and at sufficiently low temperature, and that the code states of this memory have no instability except for the inevitable one. However, we also see that the coherence power of this memory is limited by space and time. We also briefly discuss the RVB memory, which is an improvement of the Z_2 quantum memory, and the relations of our results to the obscured symmetry breaking in statistical physics.