Dual-rail cavity qubit measurements with erasure detection, Part 2: Experiment

The dual-rail cavity qubit has recently been proposed for the implementation of an erasure qubit in which the logical information is encoded within the {|01>, |10>} subspace of two superconducting microwave cavities [1]. Here, we focus on the recent experimental realization of a key element of the dual-rail cavity qubit concept: state preparation and measurement (SPAM) [2]. In part 2 of this two-part talk, we present results of the experimental demonstration of the dual-rail cavity qubit. First, we confirm that the dual-rail cavity qubit can be prepared and measured with high fidelity, showing logical misassignment errors at the 10^{-4}-level and detection efficiency of over 99% of cavity decay events as erasures, in agreement with detailed simulations. Next, we use our measurement to quantify idling errors of our dual-rail cavity qubit, extracting phase error and bit-fip error rates at least 6 and 140 times less frequently than cavity decay errors, respectively. These findings confirm a key predicted error hierarchy of the dual-rail cavity qubit, with most errors detected as erasures and the remaining errors occurring at a much smaller rate. This initial confirmation of this error hierarchy makes the dual-rail cavity qubit a viable candidate for integration into higher-level error correction codes.

[1] Teoh et al., PNAS 120 (41), e2221736120, 2023

[2] Chou et al., arXiv:2307.03169, 2023