Coherent spinor dynamics in a spin-1 Bose condensate

TL;DR

This paper demonstrates the observation and control of coherent spin-changing collisions in a spin-1 Bose-Einstein condensate, revealing Josephson-like oscillations and matter-wave four-wave mixing phenomena.

Contribution

It reports the first observation of coherent, reversible spin-changing collisions in a spin-1 Bose condensate with control over the dynamics.

Findings

Coherent spin oscillations observed in a spin-1 Bose condensate.

Determined spin-dependent scattering length as -1.45(18) Bohr.

Achieved coherent control using magnetic field-induced phase shifts.

Abstract

Collisions in a thermal gas are perceived as random or incoherent as a consequence of the large numbers of initial and final quantum states accessible to the system. In a quantum gas, e.g. a Bose-Einstein condensate or a degenerate Fermi gas, the phase space accessible to low energy collisions is so restricted that collisions be-come coherent and reversible. Here, we report the observation of coherent spin-changing collisions in a gas of spin-1 bosons. Starting with condensates occupying two spin states, a condensate in the third spin state is coherently and reversibly created by atomic collisions. The observed dynamics are analogous to Josephson oscillations in weakly connected superconductors and represent a type of matter-wave four-wave mixing. The spin-dependent scattering length is determined from these oscillations to be -1.45(18) Bohr. Finally, we demonstrate coherent control of the evolution of the system by applying differential phase shifts to the spin states using magnetic fields.