QC Research Seminar: Emulating non-Markovian Gaussian environments with trains of ancillas

A promising application of fault tolerant quantum computers is the simulation of quantum systems. In realistic settings, quantum systems interact with their surrounding environments, implying that effects of environments must be accounted for to achieve faithful simulation. It has, since the early days of quantum computing, been understood that the effects of an environment on a quantum system can be emulated by coupling to an ancillary system of comparable size. In this talk, we present a resource-efficient method for simulating the effects of any Gaussian bath independent of the system size. The method uses a stream or train of ancillary qubits to emulate the interaction between the environment and the system. Given any non-zero target accuracy and any Gaussian environment, we provide rigorous resource estimates. Notably, the method can be used to simulate strong system-environment interactions and non-Markovian effects.

The talk is based on joint work with Hans Michael Christensen and Frederik Nathan.