  We propose a non-deterministic CNOT gate based on a quantum cloner, a quantum
switch based on all optical routing of single photon by single photon, a
quantum-dot spin in a double-sided optical microcavity with two photonic
qubits, delay lines and other linear optical photonic devices. Our CNOT
provides a fidelity of 78% with directly useful outputs for a quantum computing
circuit and requires no ancillary qubits or electron spin measurements.
