2026/08/04 by Xanda C Kolesnikow, Thomas B Smith, Andrew C Doherty
Physics and Astronomy · #quant-ph
5 pages + 20 page appendix, 3 + 7 figures, comments welcome
arxiv created 2026/08/04 · arxiv updated 2026/08/05
Protected superconducting qubits such as the 0-π qubit promise to substantially suppress error rates, facilitating fault-tolerant quantum computing with fewer qubits. Measuring these qubits is challenging due to their protected nature, and thus far no concrete proposal exists for how to measure them without breaking their protection. Here we show how to perform protected measurements of the 0-π qubit in two orthogonal bases. The protection of these measurements is facilitated by their quantum non-demolition nature, allowing faults on ancillary measurement qubits to be tolerated. As experimental progress pushes protected qubits further into the low error-rate regime, our techniques will be crucial for fault-tolerant universal control.