Spying on photons with photons: quantum interference and information
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.
- 1.N. Bohr, Discussions with Einstein on Epistemological Problems in Atomic Physics (Cambridge University Press, 1949)Google Scholar
- 2.R.P. Feynman, R.B. Leighton, M. Sands, The Feynman Lectures on Physics (Addison-Wesley, Reading, MA, 1965), Vol. III, Chap. 1Google Scholar
- 9.J. Wheeler, Problems in Formulation of Physics, edited by G.T. di Francia (North-Holland, Amsterdam, 1978)Google Scholar
- 10.J. Wheeler, “Law without law” in Quantum Theory and Measurement, edited by J.A. Wheeler, W.H. Zurek (Princeton University Press, Princeton, NJ, 1983)Google Scholar
- 33.R. Loudon, The Quantum Theory of Light, 3rd edn. (Oxford University Press, 2003)Google Scholar