Coherent control of ultracold 85Rb trap-loss collisions with nonlinearly frequency-chirped light

TL;DR

This study demonstrates that the shape of nonlinearly frequency-chirped light pulses can coherently control ultracold 85Rb trap-loss collisions, with specific chirp shapes enhancing the collisional rate constant significantly.

Contribution

It introduces a method to manipulate ultracold atomic collisions using nonlinearly chirped light pulses, revealing shape-dependent effects on collisional rates.

Findings

Positive chirps show little dependence on shape for collisional rates.

Negative concave-down chirps can enhance the collisional rate by up to 50%.

Quantum simulations support experimental observations of coherence effects.

Abstract

We present results on coherent control of ultracold trap-loss collisions using 40 ns pulses of nonlinearly frequency-chirped light. The chirps, either positive or negative, sweep ~1 GHz in 100 ns and are centered at various detunings below the D2 line of 85Rb. At each center detuning, we compare the collisional rate constant beta for chirps that are linear in time, concave-down and concave-up. For positive chirps, we find that beta generally depends very little on the shape of the chirp. For negative chirps, however, we find that beta can be enhanced by up to 50(20)% for the case of the concave-down shape. This occurs at detunings where the evolution of the wavepacket is expected to be coherent. An enhancement at these detunings is also seen in quantum mechanical simulations of the collisional process.