Linear optical controlled-NOT gate in the coincidence basis
Timothy C. Ralph, Nathan K. Langford, T. B. Bell, Andrew G. White · Physical Review A · 2002
We describe the operation and tolerances of a nondeterministic, coincidence basis, quantum controlled-NOT gate for photonic qubits. It is constructed solely from linear optical elements and requires only a two-photon source for its demonstration. Its success probability is $1/9.$