Light storage in a magnetically dressed optical lattice

Differential Stark shift compensation for ground-state ${}^{87}\mathrm{Rb}$ atoms trapped in an elliptically polarized optical lattice and “magic” magnetic field was recently proposed and demonstrated experimentally by N. Lundblad et al. [e-print arXiv:0912.1528] and analyzed theoretically by A. Derevianko [e-print arXiv:0912.3233]. Here we demonstrate enhanced hyperfine coherence times using the magic field technique. We observe coherent light storage with a $0.32$-s lifetime in an atomic Rb gas confined in a one-dimensional optical lattice and magnetic field.

Figure 1

Retrieved pulse energy as a function of the magnetic field, for a 64-$\mu$K-deep lattice. Squares denote lin$\perp$lin polarizations and $m=0$ optically pumped sample, and circles and triangles denote the ${\sigma }^{\pm }/{\sigma }^{\mp }$ polarizations and unpolarized sample. Light is stored and retrieved after 0.5, 0.3, and 0.2 s, respectively. Solid curves are Gaussian fits; see text.

Figure 2

Retrieval efficiency vs storage time in a 48-$\mu$K-deep lattice at $B=4.2$ G. An exponential fit provides a lifetime of 0.32(1) s. See text for details.

Figure 3

The $1/\mathrm{e}$ lifetime determined via the storage and retrieval protocol as a function of the magnetic field in a 64-$\mu$K-deep lattice.

Figure 4

The $1/e$ lifetime of light storage and retrieval protocol vs trap depth. Memory lifetime is no longer limited by Stark shifts but by magnetic decoherence of the clock states and atomic losses.

Figure 5

$T{\tau }_{c,\pm }/(T-{\tau }_{c,\pm })$ as the function of the effective magnetic field moment ${\mu }^{\prime }\equiv \mathit{dE}/\mathit{dB}$, for the three long-lived coherences, each at its respective magic field value $B_0^{\pm ,c}$, in a 64-$\mu$K-deep trap.