Planar optical quantum computing: Current status and future challenges

We report the current status and future prospects over optical quantum computing, based on reliable, scalable, monolithically integrable planar devices. Every quantum-gate operation can be implemented using only planar 1- qubit rotations and CNOT gates, both in the universal and non-deterministic forms, using either single-photon or coherent-state sources. Therefore, any quantum algorithm, such as Quantum Fourier Transform, or Quantum Key Distribution, can be implemented using only planar optical devices.