Non-local two-photon correlations using interferometers physically separated by 35 meters

University of Geneva, Group of Applied Physics, 20 Rue de l'Ecole de Medécine CH-1211 Geneva 4, Switzerland

Corresponding author: wolfgang.tittel@physics.unige.ch

Received: 4 March 1997
Accepted: 30 October 1997

Abstract

An experimental demonstration of quantum-correlations is presented. Energy and time entangled photons at wavelengths of 704 and 1310 nm are produced by parametric downconversion in and are sent through optical fibers into a bulk-optical (704 nm) and an all-fiber Michelson-interferometer (1310 nm), respectively. The two interferometers are located 35 meters aside from one another. Using Faraday mirrors in the fiber interferometer, all birefringence effects in the fibers are automatically compensated. We obtained two-photon fringe visibilities of up to 95% from which one can project a violation of Bell's inequality by 8 standard deviations. The good performance and the auto-aligning feature of Faraday-mirror interferometers show their potential for a future test of Bell's inequalities in order to examine quantum correlations over long distances.