Noise suppression via generalized-Markovian processes

TL;DR

This paper demonstrates how adding a carefully engineered generalized-Markovian noise can reduce error rates in quantum channels, effectively extending their coherence and protecting quantum information against various noise sources.

Contribution

It introduces a novel noise engineering approach using generalized-Markovian processes to suppress errors in quantum channels, extending coherence times.

Findings

Adding generalized-Markovian noise can double or triple channel length at constant fidelity.

The method is analytically demonstrated for dephasing channels.

Numerical results show protection against thermal Markovian noise.

Abstract

It is by now well established that noise itself can be useful for performing quantum information processing tasks. We present results which show how one can effectively reduce the error rate associated with a noisy quantum channel, by counteracting its detrimental effects with another form of noise. In particular, we consider the effect of adding on top of a purely Markovian (Lindblad) dynamics, a more general form of dissipation, which we refer to as generalized-Markovian noise. This noise has an associated memory kernel and the resulting dynamics is described by an integro-differential equation. The overall dynamics are characterized by decay rates which depend not only on the original dissipative time-scales, but also on the new integral kernel. We find that one can engineer this kernel such that the overall rate of decay is lowered by the addition of this noise term. We illustrate this technique for the case where the bare noise is described by a dephasing Pauli channel. We analytically solve this model, and show that one can effectively double (or even triple) the length of the channel, whilst achieving the same fidelity, entanglement, and error threshold. We numerically verify this scheme can also be used to protect against thermal Markovian noise (at non-zero temperature), which models spontaneous emission and excitation processes. A physical interpretation of this scheme is discussed, whereby the added generalized-Markovian noise causes the system to become periodically decoupled from the background Markovian noise.