Knill, Laflamme, and Milburn recently showed that non-deterministic quantum logic operations could be performed using linear optical elements, additional photons (ancilla), and post-selection based on the output of single-photon detectors [Nature 409, 46 (2001)]. Here we report the experimental demonstration of two logic devices of this kind, a destructive controlled-NOT (CNOT) gate and a quantum parity check. These two devices can be combined with a pair of entangled photons to implement a conventional (non-destructive) CNOT that succeeds with a probability of 1/4.
@article{arxiv.quant-ph/0109128,
title = {Demonstration of Non-Deterministic Quantum Logic Operations using Linear Optical Elements},
author = {T. B. Pittman and B. C. Jacobs and J. D. Franson},
journal= {arXiv preprint arXiv:quant-ph/0109128},
year = {2009}
}