High fidelity magic state preparation in an error-detecting surface code (Part 2)

The most well-established route to achieving universal fault-tolerant quantum computation requires the preparation of so-called magic states, which can be combined with lattice surgery to implement non-Clifford logical gates. Recent theoretical progress has introduced the idea of magic state cultivation, which substantially reduces the spacetime footprint of the magic state factories required to prepare these states. Nevertheless, these factories still remain highly sensitive to the initial error of the encoded magic state, which is typically limited to the 10^-3 level set by two-qubit gate fidelities.

We propose a new scheme for preparing this initial magic state with logical error rates at the 10^-4 to 10^-5 level, by making use of the highly structured noise of dual-rail cavity qubits in a flagged, error-detected state preparation circuit. This circuit requires just five dual-rail cavity qubits and outputs a |T> state in a d=2 surface code, which can further be used for magic state cultivation in the color code, or easily grown to a larger surface code distance for use in magic state distillation.

In part 2 of this two-part talk, we present experimental results from one of our multi-qubit dual-rail systems.