Experimental macroscopic coherence by phase-covariant cloning of a single photon

TL;DR

This paper demonstrates the generation of macroscopic quantum coherence through phase-covariant cloning of a single photon, revealing nonlocal coherence transfer in a high-gain optical amplification process involving thousands of photons.

Contribution

It introduces an experimental setup for phase-covariant cloning at high gain and a novel probabilistic method to analyze the multiphoton output wavefunction.

Findings

Observation of interference fringes indicating nonlocal coherence transfer

Successful amplification of a single photon into a mesoscopic state with up to 4000 photons

Development of a new method to extract information from multiparticle quantum states

Abstract

We investigate the multiphoton states generated by high-gain optical parametric amplification of a single injected photon, polarization encoded as a ''qubit''. The experiment configuration exploits the optimal phase-covariant cloning in the high gain regime. The interference fringe pattern showing the non local transfer of coherence between the injected qubit and the mesoscopic amplified output field involving up to 4000 photons has been investigated. A probabilistic new method to extract full information about the multiparticle output wavefunction has been implemented.