Hanbury Brown and Twiss and other Quantum Correlations: from Photons to Atoms - Alain Aspect

Fifty years ago, two astronomers, R. Hanbury Brown and R. Q. Twiss, invented a new method to measure the angular diameter of stars, below the limit set by the atmospheric fluctuations. Their proposal prompted a hot debate among physicists, and it was only after the development of R Glauber's quantum analysis that the effect was fully understood as a two particle quantum interference effect. From a modern perspective, it can be viewed as an early example of the amazing properties of pairs of quantum correlated particles. The effect has now been observed with boson and fermion atoms, stressing its fully quantum character. After putting these experiments in a historical perspective, I will present recent results, and comment on their significance. I will also show how our individual atom detection scheme has allowed us to demonstrate the creation of atom pairs, paving the way to experiments aiming at probing entanglement in atom pairs.