Title: Randomised benchmarking for non-Markovian noise
Date: Sept 25, 2021 (Saturday)
Time: 14:30 - 15:30
Place: Google Meet
Link: https://meet.google.com/odw-oosb-jpw

Abstract:
 
In the far-reaching goal of reaching fault tolerance in quantum computers, setting a  benchmark for the diverse types of noise that can arise in quantum devices constitutes  one of the first steps. In the last decade, randomised benchmarking (RB) has become the  gold standard for estimating average error rates of a given gate-set with little resources.  State-of-the-art RB protocols can estimate average noise for very general gate-sets and  diverse aims, normally predicting error rates that decay as a linear combination of  exponentials in the number of gates of a computation. Deviations from an exponential  decay behaviour are generally assumed to belong to the realm of non-Markovian  (temporally correlated) noise, which has largely been unexplored theoretically in the  context of quantum errors. 

In my talk, I will describe how we employed a recently developed framework  describing non-Markovian quantum phenomena to derive an analytical expression for  the average sequence fidelity of an RB experiment with non-Markovian noise. We did  this as a first approach for the Clifford group, which can be realised efficiently on a  quantum processor. Consequently, we proposed a set of methods, implementable with  current experimental setups, to quantitatively estimate the effects of non-Markovianity  in RB, the timescales of the memory of non-Markovian noise, and to diagnose the  (in)coherence of non-Markovian noise. Our work constitutes one of the very first steps  in the characterisation of errors beyond the Markovian and time independent regime and  our methods can be directly imported in different benchmarking techniques, serving  both as a theoretical bedrock for more general development and insights, as well as a  testing ground in practical scenarios.