Dissipation alters modes of information encoding in small quantum reservoirs near criticality

TL;DR

This study explores how dissipation influences information encoding modes in small quantum reservoirs near criticality, revealing a transition from redundancy to synergy that affects memory and responsiveness.

Contribution

It introduces an information-theoretic analysis of a driven-dissipative quantum reservoir, highlighting the role of dissipation and criticality in encoding mechanisms.

Findings

Near criticality, encoding shifts from redundancy to synergy.

Synergy enhances short-term responsiveness and memory.

Dissipation promotes redundant encoding for long-term memory.

Abstract

Quantum reservoir computing (QRC) has emerged as a promising paradigm for harnessing near-term quantum devices to tackle temporal machine learning tasks. Yet identifying the mechanisms that underlie enhanced performance remains challenging, particularly in many-body open systems where nonlinear interactions and dissipation intertwine in complex ways. Here, we investigate a minimal model of a driven-dissipative quantum reservoir described by two coupled Kerr-nonlinear oscillators, an experimentally realizable platform that features controllable coupling, intrinsic nonlinearity, and tunable photon loss. Using Partial Information Decomposition (PID), we examine how different dynamical regimes encode input drive signals in terms of redundancy (information shared by each oscillator) and synergy (information accessible only through their joint observation). Our key results show that, near a critical point marking a dynamical bifurcation, the system transitions from predominantly redundant to synergistic encoding. We further demonstrate that synergy amplifies short-term responsiveness, thereby enhancing immediate memory retention, whereas strong dissipation leads to more redundant encoding that supports long-term memory retention. These findings elucidate how the interplay of instability and dissipation shapes information processing in small quantum systems, providing a fine-grained, information-theoretic perspective for analyzing and designing QRC platforms.