Operator dynamics in k-Markov random circuits

TL;DR

This paper explores how k-Markov sequences of unitary gates can be used to control information spreading, scrambling, and correlations in quantum circuits more efficiently than traditional methods.

Contribution

It introduces the use of k-Markov processes to manipulate operator transport, scrambling time, and correlation structures in quantum circuits, providing new control mechanisms.

Findings

k-Markov sequences control operator transport effectively

They can manipulate scrambling time and correlation structures

Equivalent to non-uniform distributions in brickwork circuits

Abstract

We demonstrate that $k$-Markov sequences of unitary gates provide low-cost handles to manipulate the rate and structure of information spreading compared to traditional random, 0-Markov, circuits. For SWAP gates and brickwork circuits, we use graph cover time to demonstrate how $k$-Markov processes can be used to control operator transport. With SWAP gates and the set of Clifford gates that can change operator weight, we show how $k$-Markov sequences can be used to manipulate scrambling time and generate novel structures of spatial-temporal correlations across a qubit network. We show that $k$-Markov circuits constructed from PSWAP gates at fixed angle are equivalent to standard brickwork circuits with PSWAP angle drawn from non-uniform distributions generated by the $k$-Markov process. In those circuits, the time evolution of the average Hamming weight and the space-time correlation structure after equilibrium again vary significantly from the 0-Markov case, depending on the transition probabilities of the process.