Connection between memory performance and optical absorption in quantum reservoir computing

TL;DR

This paper explores how optical absorption influences the memory capacity of quantum reservoir computers, revealing an optimal dissipation level that enhances their short-term memory performance.

Contribution

It establishes a direct connection between optical absorption and quantum reservoir computing performance, introducing tunable dissipation as a control parameter.

Findings

Optimal dissipation enhances memory capacity.

A tunable qubit decay controls fading memory.

Identified a regime for maximum memory performance.

Abstract

The fading memory property is a key requirement for reservoir computers -- a specific type of recurrent neural network with fixed internal weights. While mostly undesired in gate-based quantum computing, dissipation due to material imperfections or coupling to the environment acts as a natural mechanism intrinsically providing fading memory to reservoir computers based on dynamical open quantum systems. In this work, we unravel a connection between the physical metric of optical absorption and the performance of quantum reservoir computers in terms of their short-term memory capacity. We establish this link by considering a coherent input encoding in conjunction with tunable qubit decay, giving precise control over the fading memory in the quantum reservoir computer. Our analysis enables us to identify a sweet-spot regime for the dissipation strength at which memory performance is maximized.