Physical Review A

Control of spin current in a Bose gas by periodic application of π pulses

Yujiro Eto, Mark Sadgrove, Sho Hasegawa, Hiroki Saito, Takuya Hirano

Published Jul 28, 2014• 16 citations

Abstract

We generate spin currents in an $^{87}\mathrm{Rb}$ 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 $\ensuremath{\pi}$ 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.

DOI: 10.1103/physreva.90.013626

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Physical Review A

Control of spin current in a Bose gas by periodic application of π pulses

Yujiro Eto, Mark Sadgrove, Sho Hasegawa, Hiroki Saito, Takuya Hirano

Published Jul 28, 2014• 16 citations

Publisher

Abstract

We generate spin currents in an

^{87}\mathrm{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

\ensuremath{\pi}

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.

DOI: 10.1103/physreva.90.013626

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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.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.

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arXiv:1008.4428Physical Review AJan 28, 20114 citations

We generate spin currents in an

^{87}\mathrm{Rb}

\ensuremath{\pi}

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.

0.75

at the evolution time of

1.5

s. Mean-field theory consistently predicts higher visibility than experimentally observed values. We quantify the effects of classical and quantum noise and infer a coherence time of

2.8

s for a trapped condensate of $5.5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ interacting atoms.

We study the collapse and revival of coherence induced by dipolar spin waves in a trapped gas of

^{87}\mathrm{Rb}

atoms. In particular, we observe spatially localized collapse and revival of Ramsey fringe contrast and show how the pattern of coherence depends on the strength of the spin-wave excitation. We find that the spatial character of the coherence dynamics is incompatible with a simple model based only on position-space overlap of wave functions. We show that this phenomenon requires a full phase-space description of the atomic spin using a quantum Boltzmann transport equation, which highlights spin-wave-induced coherent spin currents and the ensuing dynamics they drive.