Two-Particle Four-Mode Interferometer for Atoms (poster)

• We present a free-space interferometer to observe two-particle interference of a pair of atoms with entangled momenta. • The source of atom pairs is a Bose-Einstein condensate subject to a dynamical instability, and the interferometer is realized using Bragg diiraction on optical lattices. • Our observations rule out the possibility of a purely mixed state at the input of the interferometer. • Our current setup can be extended to enable a test of a Bell inequality on momentum observables. Bragg mirror and splitters momentum energy excited state • Mirror: 100 µs pulse (π-pulse) • Splitter: 50 µs pulse (π/2-pulse) • The lasers imprint their phase on the atomic modes (φ A,B) • Spectral broadening induced by the short interaction time: → the same lattice addresses (p,-p') and (-p, p') → addition of a velocity-dependent phase away from the energy resonance • Correlation coefficient: E = V cos(φ A-φ B-2δτ) Interferometer diagram • Input state: • Joint detection probabilities: • Correlation coeecient: • Violation of a Bell inequality if V > 1/√2 Source of atom pairs quasimomentum in the lattice frame energy lowest Bloch band 1st BZ • Dynamical instability driven by moving optical lattice → emission of atom pairs with opposite momenta • Broad resonance → several pairs of modes are coherently populated • Filtering the data reduces the state to the desired form: center-of-mass frame • Analysis of 3 diierent sets of modes → access to 3 diierent phases (φ A-φ B-2δτ)