NONLINEAR MATTER-WAVE AMPLIFICATION IN A 23Na SPINIOR BOSE-EINSTEIN CONDENSATE

 

Jonathan Wrubel, Hyewon Pechkis, Paul Griffin, Ryan Barnett, Eite Tiesinga, William D. Phillips, and Paul Lett

National Institute of Standards and Technology

Gaithersburg, MD 20899

 

An F = 1, 23Na Bose-Einstein condensate (BEC) in a far off-resonant optical trap has a spinor order parameter for the hyperfine sublevels mF = +1, 0, −1. At low magnetic fields, pairs of atoms may undergo spin-changing collisions between the |mFA,mFB>= |0, 0 > and | +1, −1 > states. The ground state is a BEC in the mF = 0 state. However, by dressing the F = 1 energy levels with a microwave field off-resonant from the F = 2 state, the sign of the effective quadratic Zeeman energy is reversed and the mF = 0 BEC becomes metastable. Vacuum fluctuations in the initially empty mF =+1,−1 states drive nonlinear amplification of |+1,−1> atom pairs.  When the energy difference is equal to an interaction energy, then the rate of emission of |+1, −1 > pairs is maximal. This realizes a parametric amplifier for matter waves and is characterized by sub- shot-noise spin correlations between the mF = +1 and mF = −1 BECs.  We discuss progress in realizing this amplifier in a Na BEC.