Simulation complexity in noisy quantum systems

Presented by Sayonee Ray, University of Waterloo and 1Qbit

In this talk, I will discuss simulation complexity of macroscopic observables in noisy (open) quantum systems. I will revisit the question of how decoherence limits the growth of complexity of a simulation in an interacting system. First, I will begin by discussing what kind of simulations are hard to do classically and which might not be. I will then talk about how interactions can lead to the growth of complexity in a closed system. To understand this better, I will discuss a toy model of a bosonic mode under Kerr interactions. This system is exactly solvable but is a good testbed to understand how interactions can lead to non-Gaussian features and negativity in Wigner function, and how decoherence can limit both. I will end by discussing how Gaussian (classical) approximation can still be used to simulate certain properties of this interacting system, and when it fails.