Suppressing errors in quantum circuits using real-time, closed-loop feedback*

Realizing quantum circuits of practical relevance requires accurate, real-time control over all parameters of a large quantum processor, which fluctuate on short timescales due to coupling to environmental noise. Here, building on prior work with single qubits [1], we introduce a framework for using real-time, closed-loop feedback to stabilize frequency fluctuations in a grid of tunable transmons interacting via tunable couplers. We investigate different strategies for estimating frequency corrections and explore how feedback allows the system’s tunability to be exploited for optimization without sacrificing device performance significantly. Combining these techniques, we study how our framework suppresses errors in multi-qubit quantum circuits that are vital for the realization of quantum error correction, including controlled-Z gates and parity check cycles.

[1] A. Vepsäläinen, R. Winik, et al., Nature Communications 13, 1932 (2022) | arXiv:2105.01107 (2021)