Light storage in atomic vapor

We study coherent optical excitations of atoms in a hot vapor. We develop new techniques for quantum memories that optimize bandwidth, storage time, and fidelity. 

Future quantum photonic networks and information processors will require coherent optical memories for single photons, known as quantum memories. In particular, Quantum memories are needed for synchronizing photonic sources and gates. We study coherent optical memories that map the optical field onto a long-lived electronic state of gaseous atoms in a controlled and reversible manner. 

In one project, we store light on the electronic orbitals of rubidium vapor via stimulated two-photon absorption. Employing purely-orbital transitions enables high bandwidth and low noise. The memory lifetime is 10 times longer than the stored nanosecond-long light pulses. Such a memory can enable the efficient synchronization of probabilistic single photon sources and two-photon logic gates.

In a second project, we store light on the electronic spin in the ground state of cesium vapor. Most hot-vapor memories use dense gases, where the random collisions between the atoms dominate the coherence times of the electronic spins. As a result, in most experiments the memory lifetime is limited to a few milliseconds only. We develop a storage scheme that is insensitive to the spin-exchange collisions and reach storage lifetimes longer than 100 milliseconds.

To learn about the effect of spatial diffusion on stored light in atomic vapors, see our page on coherent diffusion of polaritons.

Mapping of (left) the polarization of the photons onto (right) the electronic spin of cesium atoms