Measuring a photonic qubit without destroying it.
Measuring the polarization of a single photon typically results in its destruction. We propose, demonstrate, and completely characterize a quantum nondemolition (QND) scheme for realizing such a measurement nondestructively. This scheme uses only linear optics and photodetection of ancillary modes to induce a strong nonlinearity at the single-photon level, nondeterministically. We vary this QND measurement continuously into the weak regime and use it to perform a nondestructive test of complementarity in quantum mechanics. Our scheme realizes the most advanced general measurement of a qubit to date: it is nondestructive, can be made in any basis, and with arbitrary strength.
Pryde
G J
GJ
Centre for Quantum Computer Technology, Department of Physics, University of Queensland, Brisbane 4072, Australia.
O'Brien
J L
JL
White
A G
AG
Bartlett
S D
SD
Ralph
T C
TC