Interferometer and method for controlling the coalescence of a pair of photons

Abstract

An interferometer for controlling the coalescence of a pair of photons, including: an optical source, which generates a first and a second pump pulse coherent with each other and shifted in time by a delay; and a first interferometric stage, which receives the first pump pulse and generates an antisymmetric state with two coalescent photons (1/√{square root over (2)}(|2,0−|0,2)). The interferometer also includes a second interferometric stage, which receives the second pump pulse and generates a symmetric state with two coalescent photons (1/√{square root over (2)}·(|2,0+|0,2)), the first and the second interferometric stages being connected in a manner such that the interferometer outputs a final state equal to a weighted sum of the antisymmetric state and of the symmetric state (1/√{square root over (2)}·(|2,0+|0,2)+e·1/√{square root over (2)}·(|2,0−|0,2)), the weights of the sum being a function of the delay.