Proposal for a two-qubit quantum phase gate for quantum photonic integrated circuits

We propose a protocol for a two-qubit quantum phase gate based upon the reflection of photon pulses from a quantum dot in a cavity. Depending on the state of the quantum dot the reflected photons acquire a conditional phase shift. The key ingredient is the ultrafast control of the quantum dot energies by electric fields, which allows for tuning the exciton and biexciton successively into resonance with the cavity mode. The complete dynamics of the gate are simulated, revealing a fidelity of about 0.9. The proposed scheme uses position coding and is therefore well suited to the implementation in an integrated photonic quantum processor.