Universal fault-tolerant operation of a logical qubit in silicon

Fault-tolerant quantum computation offers a path to perform high-fidelity quantum information processing from noisy components, where logical errors can be suppressed to arbitrarily low rates using quantum error correction. We demonstrate universal fault-tolerant quantum operations with a logical qubit in a silicon quantum device. In this presentation, we will discuss the control and calibration techniques used for manipulating Schrödinger spin-cat qubit encoded on the spin-7/2 nucleus of an antimony (123Sb) atom [1], and highlight potential applications of high-dimensional systems for quantum error correction. Utilizing a phase-corrected logical qubit, we implement fault-tolerant quantum circuits for logical encoding and decoding, quantum error correction, as well as universal gates, exploiting a way to circumvent the restrictions of the Eastin-Knill no-go theorem without additional resources [2]. We realize high-fidelity logical state preparation and measurement, show extension of logical lifetime with quantum error correction, and implement universal fault-tolerant gates with better-than-physical qubit performance while maintaining more than 90% acceptance rate. Our results present the logical control of an atom in a semiconducting device for fault-tolerant quantum computation with low overhead.

[1] Xi Yu et al. Creation and manipulation of Schrödinger cat states of a nuclear spin qudit in silicon. 2024. arXiv: 2405.15494 [quant-ph].

[2] Pragati Gupta, Andrea Morello, and Barry C. Sanders. Universal transversal gates. 2024. arXiv: 2410.07045 [quant-ph].