Error-detected entangling gate operations between dual-rail cavity cavity qubit – Part 1

Encoding dual-rail qubits in superconducting cavities is a promising platform which exhibits a strong hierarchy of errors. In these qubits the dominant error, single photon loss, may be detected and either post-selected or converted to an erasure. The remaining undetectable errors due to cavity dephasing are expected to be much smaller, creating a favorable error hierarchy. It is crucial that this error hierarchy is preserved throughout all qubit operations, especially the two-qubit gate. In part 1, we describe a novel approach for realizing such a two-qubit gate which implements a control-Z gate between dual-rail cavity qubits. This protocol simply relies on engineering a dispersive interaction directly between the two qubits. With detailed analysis of both the photon loss and residual post-selected errors we confirm the error hierarchy is indeed preserved, and that we can now achieve fast, high-fidelity two qubit gates in the dual-rail architecture.