Measuring a photonic qubit without destroying it

Abstract

A nondeterministic scheme for general measurement of a flying qubit was demonstrated and characterized. The first set of fidelity measures were introduced to characterize the quality of quantum nondemolition (QND) measurement. This measurement uses only linear optics and photodetection of ancillary modes to induce a strong nonlinearity at the single-photon level. It was found that this QND measurement vary continuously into the weak regime and use to perform a nondestructive test of complementarity in quantum mechanics. Show more