We introduce a low-overhead approach for detecting errors in arbitrary
Clifford circuits on arbitrary qubit connectivities. Our method is based on the
framework of spacetime codes, and is particularly suited to near-term hardware
since it has a much milder overhead in qubits and gates compared to error
correction, while achieving a better sampling overhead than existing error
mitigation methods. We present efficient algorithms for finding valid checks
that are simultaneously low weight, satisfy connectivity constraints, and cover
large detecting regions within the circuit. Using this approach, we
experimentally demonstrate error detection on circuits of up to 50 logical
qubits containing 2450 CZ gates, and show physical to logical fidelity gains of
up to $236\times$. Furthermore, we show our algorithm can efficiently find
checks in universal circuits, but the space of valid checks diminishes
exponentially with the non-Cliffordness of the circuit. These theoretical and
experimental results suggest that Clifford-dominated circuits are promising
candidates for near-term quantum advantage.

Questo articolo esplora i giri e le loro implicazioni.

Scarica PDF: