Cutting multi-control quantum gates with ZX calculus
Circuit cutting, the decomposition of a quantum circuit into independent
partitions, has become a promising avenue towards experiments with larger
quantum circuits in the noisy-intermediate scale quantum (NISQ) era. While
previous work focused on cutting qubit wires or two-qubit gates, in this work
we introduce a method for cutting multi-controlled Z gates. We construct a
decomposition and prove the upper bound $\mathcal{O}(6^{2K})$ on the associated
sampling overhead, where $K$ is the number of cuts in the circuit. This bound
is independent of the number of control qubits but can be further reduced to
$\mathcal{O}(4.5^{2K})$ for the special case of CCZ gates. Furthermore, we
evaluate our proposal on IBM hardware and experimentally show noise resilience
due to the strong reduction of CNOT gates in the cut circuits.
Christian Ufrecht Maniraman Periyasamy Sebastian Rietsch Daniel D. Scherer Axel Plinge Christopher Mutschler