Cat-alyzing Quantum Computing

Quantum computing with light requires creating complex, non-Gaussian states of light to perform advanced computations and correct quantum errors. In their current article, the Nano Optics Group (Oliver Benson) showed a smart way to build these specialized light states, squeezed "Schrödinger cat" states. Instead of relying only on standard laser manipulation, they combined a squeezed light beam with single photons using a beam splitter and a photon detector. This setup acts like a shortcut: it increases the quality and accuracy of the target quantum states while achieving success rates as high as 43%. The authors mapped out exact settings to make this work efficiently and calculated how much real-world equipment loss the system can handle while still keeping its powerful quantum edge. Find more information in the full Article.

Introduction

Non-Gaussian quantum states and operations constitute essential resources for achieving quantum computational advantage and enabling quantum error correction in bosonic platforms. However, their generation in optical settings remains a challenging experimental task, often relying on probabilistic heralded protocols. Here, we present an in-depth analysis of the suitability of photon catalysis between low number Fock states and squeezed states for the generation of squeezed coherent state superpositions. We employ the stellar rank formalism to characterize the non-Gaussian complexity of input resources (including both states and measurements) and the generated states. This enables a systematic comparison of the fidelity between the catalyzed output and the target states to the maximum fidelity achievable by any protocol with the same non-Gaussian input resources. In this sense, we identify instances where the catalysis protocols considered here are provably optimal. We identify parameter regimes in which high-fidelity approximations of the target states can be achieved with minimal resources. Furthermore, we benchmark the performance of photon catalysis against Gaussian boson sampling-inspired protocols in terms of success probability and state quality, highlighting the advantages of deterministic Fock state sources. We also investigate the generation of related non-Gaussian resources including squeezed Fock states relevant for quantum error correction. To account for experimental imperfections, we model losses across all optical modes using a Hilbert space truncation approach in the Fock basis and analyze the robustness of the generated states under realistic conditions. Our results quantify the trade-offs between non-Gaussian resource complexity, achievable fidelity, and losses in photon catalysis protocols, providing practical guidelines for near-term photonic implementations.