Creation of Long-Term Coherent Optical Memory via Controlled Nonlinear Interactions in Bose-Einstein Condensates

A Bose-Einstein condensate confined in an optical dipole trap is used to generate long-term coherent memory for light, and storage times of more than 1 s are observed. Phase coherence of the condensate as well as controlled manipulations of elastic and inelastic atomic scattering processes are utilized to increase the storage fidelity by several orders of magnitude over previous schemes. The results have important applications for creation of long-distance quantum networks and for generation of entangled states of light and matter.

Figure 1

(a) The internal quantum states for sodium atoms used in our experiment. (b) Shadow images of a BEC in the optical dipole trap. (c) Schematic drawing of the experimental setup.

Figure 2

(a) Calculated imaginary part of $a_{12}$ as a function of the bias magnetic field. (b) Measured decay time, $\tau$, for the atom number in the ${\psi }_2$ matter wave imprint (coexisting with the ${\psi }_1$ component) vs the bias magnetic field. The insert shows the number of $|2⟩$ atoms as a function of time at $B=132.4\mathrm{G}$. The data are fitted to an exponential curve with a decay time of 540 ms.

Figure 3

(a) Probe light pulse slowed to $10\mathrm{m}/\mathrm{s}$ and transmitted all the way through a BEC (the reference pulse is recorded with no atoms present). (b)–(e) Images of the ${\psi }_2$ matter wave imprint at 1 ms, 10 ms, 20 ms, and 50 ms, respectively, after the coupling laser beam is switched off at the time indicated by an arrow in (a). (f) Same as (e) with addition of a magnetic field gradient of $200\mathrm{mG}/\mathrm{cm}$.

Figure 4

Regenerated probe light pulses after storage times of $10\mu \mathrm{s}$, 50 ms, 100 ms, 200 ms, 500 ms, 800 ms, 1.1 s, and 1.5 s, respectively. Dashed curves indicate the intensity of the coupling beam that has a peak Rabi frequency of 12 MHz.

Figure 5

(a) Regenerated probe light pulse is detected with inclusion of a third ARP step which creates the 3-level system necessary for generation of the probe field via stimulated matter wave scattering. (b) Without the third ARP step, no probe pulse is regenerated.