States reach error rates for fault-tolerant quantum memory

Sheron Blair, Francesco Arzani, Giulia Ferrini, and Alessandro Ferraro demonstrate error probabilities below the threshold for fault-tolerant memory using concatenated GKP-stabilizer codes. The researchers numerically optimized the generation of GKP states from vacua using circuits comprised solely of universal continuous-variable gates, addressing a long-standing question in the field. This work builds directly on the 1999 Lloyd and Braunstein paper in Phys. Rev. Lett. 82, 1784, establishing a lineage to foundational work in continuous-variable quantum computation. Achieving this demonstrates that universal CV gates can enable encoded fault tolerance, a critical step toward scalable quantum memory. GKP code states of sufficient quality for fault-tolerant quantum memory can now be prepared using a finite set of gates, a development that addresses a fundamental gap in continuous-variable (CV) quantum computation. The work focuses on demonstrating encoded universal computation and establishing the LB model as a fully fledged framework for fault tolerance, rather than achieving full fault-tolerant quantum computation at this stage. The LB universality hinges on the ability to host a finite set of…