Quantum state preparation and conditional coherence.
It is well known that spontaneous parametric down-conversion can be used to probabilistically prepare single-photon states. We have performed an experiment in which arbitrary superpositions of zero- and one-photon states can be prepared by appropriate postselection. The optical phase, which is meaningful only for superpositions of photon number, is related to the relative phase between the zero- and one-photon states. Whereas the light from spontaneous parametric down-conversion has an undefined phase, we show that this technique collapses one beam to a state of well-defined optical phase when a measurement succeeds on the other beam.
Resch
K J
KJ
Department of Physics, University of Toronto, 60 St. George Street, Toronto ON M5S 1A7, Canada.
Lundeen
J S
JS
Steinberg
A M
AM