Production of Ultracold Molecules with Chirped Nanosecond-Time-scale Pulses

We describe quantum simulations of ultracold $^{87}$Rb$_{2}$ molecule formation using photoassociation with nanosecond-time-scale pulses of frequency chirped light. In particular, we compare the case of a linear chirp to one where the frequency evolution is optimized by local control of the phase, and find that local control can provide a significant enhancement. The resulting optimal frequency evolution corresponds to a rapid jump from the photoassociation absorption resonance to a downward transition to the target state, a bound level of the lowest triplet state. We also consider the case of two frequencies and investigate interference effects. The assumed chirp parameters should be achievable with nanosecond pulse shaping techniques and are predicted to provide a significant enhancement over recent experiments [PRA 87, 011401(R) (2013)] with linear chirps. This work is supported by DOE and BSF.