Demonstration and characterization of a detector for minimally destructive detection of Bose condensed atoms in real time

We present the first detector that is capable of recording high-bandwidth atom number density measurements of a Bose-Einstein condensate, with a readout of the data in real time. It is based on a shot-noise-limited unbalanced Mach-Zehnder interferometer designed for a minimally destructive measurement of the atom column density of a Bose-Einstein condensate. The shot-noise limit is reached by phase modulating the laser in one arm and phase locking the interferometer with a secondcolor laser. The detector is characterized, and its sensitivity for a fractional change in the column density of a Bose-Einstein condensate is calculated. With this detection system it may be possible to implement feedback to stabilize a Bose-Einstein condensate or an atom laser.