Single-photon Input Research Articles

Optimal cloning of single-photon polarization by coherent feedback of beam splitter losses

Light fields can be amplified by measuring the field amplitude reflected at a beam splitter of reflectivity R and adding a coherent amplitude proportional to the measurement result to the transmitted field. By applying the quantum optical realization of this amplification scheme to single-photon inputs, it is possible to clone the polarization states of photons. We show that optimal cloning of single-photon polarization is possible when the gain factor of the amplification is equal to .

Creation of maximally entangled photon-number states using optical fiber multiports

We theoretically demonstrate a method for producing the maximally path-entangled state (1/Sqrt[2]) (|N,0> + exp[iN phi] |0,N>) using intensity-symmetric multiport beamsplitters, single photon inputs, and either photon-counting postselection or conditional measurement. The use of postselection enables successful implementation with non-unit efficiency detectors. We also demonstrate how to make the same state more conveniently by replacing one of the single photon inputs by a coherent state.

Quantum multi-particle interference due to a single-photon state

Quantum interference of a multi-particle is demonstrated in a simple arrangement in which the photon distribution at the output of a lossless beamsplitter for an N-photon state input at one of its input ports is dramatically changed by a single-photon state input at the other port. By a simple argument, we find that the effect persists even if the N-photon state is replaced by an arbitrary state of light.