Sub-Bath Cooling in Bosonic Systems: Gaussian Constraints and Non-Gaussian Enhancements

TL;DR

This paper establishes fundamental limits on cooling bosonic quantum systems, highlighting how non-Gaussian interactions can surpass Gaussian constraints to achieve more efficient cooling.

Contribution

It develops a framework for CV system cooling, deriving bounds for Gaussian operations and demonstrating non-Gaussian enhancements for improved cooling performance.

Findings

Derived a bound on Gaussian cooling performance applicable to all architectures.

Identified an optimal protocol minimizing energy dissipation for given ancilla resources.

Showed that non-Gaussian interactions can enhance cooling by a factor of p.

Abstract

Cooling quantum systems with finite resources is a central task in quantum technologies and has been extensively explored in discrete-variable settings. As continuous-variable (CV) platforms play an increasingly important role in quantum information processing, it becomes crucial to understand the fundamental limitations of cooling bosonic systems. In this work, we develop a general framework for cooling CV systems, identifying both the constraints imposed by Gaussianity and the advantages enabled by non-Gaussian interactions. We derive a reachable bound on the cooling performance of Gaussian operations that applies to arbitrary cooling architectures. By optimizing over all protocols saturating this bound, we further identify the most efficient scheme, which minimizes dissipated energy for a given number of ancilla modes. Beyond Gaussian operations, we show that $p$-excitation exchange exploits non-Gaussian resources to achieve a $p$-fold enhancement of the cooling limit. Our results establish the fundamental limits of CV heat-bath algorithmic cooling and reveal the crucial role of non-Gaussianity in surpassing Gaussian cooling barriers.