YQI Talk - Qian Xu - University of Chicago

Designing fault-tolerant protocols that leverage specific hardware characteristics and noise profiles is a promising avenue for bridging the gap between the current NISQ era and the future of fault tolerance. In this talk, I will present new fault-tolerant schemes tailored for bosonic systems and neutral atom arrays. For bosonic systems that feature infinite-dimensional Hilbert spaces, we develop new error-corrected bosonic qubits and operations in a hardware-efficient and fully fault-tolerant manner. First, I will present a new stabilized bosonic qubit that not only possesses an exponential noise bias but also autonomously corrects the predominant photon losses based on the squeezed cat code. Second, we construct a universal set of error-corrected operations for the four-legged cat qubit by leveraging the strong qudit-oscillator interaction in circuit quantum electrodynamics architecture. Both schemes enable low-overhead and high-threshold concatenated fault tolerance using error-correcting bosonic qubits. For reconfigurable atom arrays with long-range qubit connectivity, I will present a constant-overhead fault-tolerant quantum computing scheme using quantum low-density-parity-check (qLDPC) codes. I will also discuss potential implementation of such qLDPC-based fault tolerance in modular superconducting architecture. These hardware-specific strategies can significantly reduce the resource demand associated with standard fault tolerance, thereby bringing large-scale quantum computing closer to realization.