Control of spin current in a Bose gas by periodic application ofπpulses

Abstract

We generate spin currents in an 87 Rb spin-2 Bose-Einstein condensate by application of a magnetic field gradient. The spin current destroys the spin polarization, leading to a sudden onset of two-body collisions. In addition, the spin coherence, as measured by the fringe contrast using Ramsey interferometry, is reduced drastically but experiences a weak revival due to in-trap oscillations. The spin current can be controlled using periodic π pulses (bang-bang control), producing longer spin-coherence times. Our results show that spin coherence can be maintained even in the presence of spin currents, with applications to quantum sensing in noisy environments.

Quantum lock-in detection of a vector light shift

“…The fictitious magnetic field gradient also causes nonlinear spin evolution and thus a population change, as does the real magnetic field gradient [25]. The initial polarized atomic spin state breaks due to the spin mixing seeded by the nonlinear spin evolution.…”

Rebuilding of destroyed spin squeezing in noisy environments

“…With numerical simulations, we find all these dynamical decoupling sequences with hard pulses suppress well the stray magnetic fields' effect with a short enough pulse delay τ. However, in a real spin-1 condensate experiment, the pulse delay is lower bounded by the π-pulse width, which is in the order of 20 µs according to Eto et al's report 43 , and upper bounded by the the driven-OAT pulse delay T c /3. To satisfy the hard pulse approximation, we must choose τ as long as possible.…”

Generalized parametric resonance in a spin-1 Bose-Einstein condensate

“…The effect of nonlinear term in Eq. ( 6) may play a role if the transversal field B x ∼ 1 µG, which is possible in a magnetic shielding room [33,34]. In Eq.…”