High photon number path entanglement in the interference of spontaneously downconverted photon pairs with coherent laser light

Abstract

We show that the quantum interference between downconverted photon pairs and photons from coherent laser light can produce a maximally path entangled N-photon output component with a fidelity greater than 90% for arbitrarily high photon numbers. A simple beam splitter operation can thus transform the 2-photon coherence of down-converted light into an almost optimal N-photon coherence.

5 pages, including 2 figures and 1 table, final version for publication as rapid communication in Phys. Rev. A

Cited by in corpus (2)

• All path-symmetric pure states achieve their maximal phase sensitivity in conventional two-path interferometry
• Quantum enhancement of N-photon phase sensitivity by interferometric addition of down-converted photon pairs to weak coherent light