Spying on photons with photons: quantum interference and information
Extreme Light Infrastructure – Nuclear Physics (ELI-NP), 30 Reactorului Street, 077125 Magurele, Romania
Received: 29 April 2016
Received in final form: 7 June 2016
Published online: 2 August 2016
The quest to have both which-path knowledge and interference fringes in a double-slit experiment dates back to the inception of quantum mechanics (QM) and to the famous Einstein-Bohr debates. In this paper we propose and discuss an experiment able to spy on one photon’s path with another photon. We modify the quantum state inside the interferometer as opposed to the traditional physical modification of the “wave-like” or “particle-like” experimental setup. We are able to show that it is the ability to harvest or not which-path information that finally limits the visibility of the interference pattern and not the “wave-like” or “particle-like” experimental setups. Remarkably, a full “particle-like” experimental setup is able to show interference fringes with 100% visibility if the quantum state is carefully engineered.
Key words: Quantum Optics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2016