Time-domain atom interferometry across the threshold for Bose-Einstein condensation

Time domain interferometry experiments were performed with matter waves trapped in a harmonic potential above and below the Bose-Einstein phase transitions. The system with a sequence of two identical radio frequency (rf) pulses separated by a delay time T was prepared. The double Bose-Einstein condensate (BEC) system was described by a spinor wave function. A quantitative explanation was given in terms of the phase evolution due to the entanglement between the internal and external degrees of freedom.