Optimization of a cavity-QED system for fast two-qubit gates

Cavity quantum electrodynamics (cQED) enables deterministic controlled gates between neutral atom and photon qubits, such as the controlled phase flip (CPF) gate [1] , which is a key component for implementing quantum computation. The gate fidelity drops sharply when the length of an input-photon pulse is shorter than the inverse of the bandwidth of a cavity, because of the distortion of the output pulse. This limits the operational speed of the gates. One way to boost the limit of gate speed may be to reduce cavity length, since this increases the bandwidth of the cavity with keeping high cooperativity [2] .