Scalable Optical Quantum State Synthesizer with Dual-Mode Resonator Memory

Optical quantum computing is a promising approach for achieving large-scale quantum computation. While Gaussian operations have been successfully scaled, the inherently weak nonlinearity in optics makes generating highly non-Gaussian states a critical challenge for universality and fault tolerance. Here, we propose and experimentally demonstrate a scalable method to generate optical non-Gaussian states with a resonator-based quantum memory that supports continuous-time storage and retrieval, in contrast to conventional loop-based memories. We introduce a dual-mode operation of the memory, enabling both storage and entangling functionalities within a single device. By employing a time-domain-multiplexed approach, we successfully demonstrate both cat and Gottesman-Kitaev-Preskill breeding protocols in a scalable fashion, marking a key step toward quantum error correction. Our experiment also marks the first full demonstration of an optical resonator memory performing writing, storage, and readout operations. We validate the memory by storing squeezed single-photon states with up to 93% total efficiency, and measure an energy relaxation time <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msub> <a:mi>T</a:mi> <a:mn>1</a:mn> </a:msub> <a:mo>=</a:mo> <a:mrow> <a:mn>2.3</a:mn> </a:mrow> <a:mspace width="0.2em"/> <a:mtext fontfamily="times">μ</a:mtext> <a:mrow> <a:mi mathvariant="normal">s</a:mi> </a:mrow> </a:math> and dephasing time <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:msub> <f:mi>T</f:mi> <f:mi>ϕ</f:mi> </f:msub> <f:mo>=</f:mo> <f:mrow> <f:mn>0.96</f:mn> </f:mrow> <f:mspace width="0.2em"/> <f:mtext fontfamily="times">μ</f:mtext> <f:mrow> <f:mi mathvariant="normal">s</f:mi> </f:mrow> </f:math> . These results establish a scalable pathway to generating complex non-Gaussian states required for fault-tolerant optical quantum computing. Beyond computation, our techniques provide new tools for enhancing quantum communication, sensing, and metrology.