Sarah E. Beavan

Photon-echo quantum memories in inhomogeneously broadened two-level atoms

Here, we propose a solid-state quantum memory that does not require spectral holeburning, instead using strong rephasing pulses like traditional photon-echo techniques. The memory uses external broadening fields to reduce the optical depth and so switch off the collective atom-light interaction when desired. The proposed memory should allow operation with reasonable efficiency in a much broader range of material systems, for instance Er{sup 3+} doped crystals which have a transition at 1.5 {mu}m. We present analytic theory supported by numerical calculations and initial experiments.

Nonclassical photon streams using rephased amplified spontaneous emission

Laser Physics Centre, RSPhysSE, Australian National University, Canberra, ACT 0200, Australia(Dated: November 20, 2009)We present a fully quantum mechanical treatment of optically rephased photon echoes. Theseechoes exhibit noise due to amplified spontaneous emission, however this noise can be seen as aconsequence of the entanglement between the atoms and the output light. With a rephasing pulseone can get an “echo” of the amplified spontaneous emission, leading to light with nonclassicalcorrelations at points separated in time, which is of interest in the context of building wide bandwithquantum repeaters. We also suggest a wideband version of DLCZ protocol based on the same ideas.

Storage and retrieval of collective excitations on a long-lived spin transition in a rare-earth ion-doped crystal

Robust, long-lived optical quantum memories are important components of many quantum information and communication protocols. We demonstrate coherent generation, storage, and retrieval of excitations on a long-lived spin transition via spontaneous Raman scattering in a rare-earth ion-doped crystal. We further study the time dynamics of the optical correlations in this system. This is the first demonstration of its kind in a solid and an enabling step toward realizing a solid-state quantum repeater.

Single photon production by rephased amplified spontaneous emission

The production of single photons using rephased amplified spontaneous emission is examined. This process produces single photons on demand with high efficiency by detecting the spontaneous emission from an atomic ensemble, then applying a population-inverting pulse to rephase the ensemble and produce a photon echo of the spontaneous emission events. The theoretical limits on the efficiency of the production are determined for several variants of the scheme. For an ensemble of uniform optical density, generating the initial spontaneous emission and its echo using transitions of different strengths is shown to produce single photons at 70% efficiency, limited by reabsorption. Tailoring the spatial and spectral density of the atomic ensemble is then shown to prevent reabsorption of the rephased photon, resulting in emission efficiency near unity.

Cavity enhanced rephased amplified spontaneous emission

In this paper we report the first demonstration of “cavity enhanced rephased amplified spontaneous emission”. The rephased amplified spontaneous emission (RASE) protocol provides an all-in-one photon-pair source and quantum memory that has applications as a quantum repeater node. Cavity enhancement of the interaction of the optical mode with the ensemble has the potential to improve the fidelity of the entanglement of the photon pairs. Using heterodyne detection, amplified emission and photon echo induced rephased amplified emission were observed from a Pr3+ doped Y2SiO5 crystal placed in a Fabry Perot cavity with a finesse of 70. Modifications to the experiment to allow non-classical correlations to be observed are discussed.

Rephasing Spontaneous Emission in a Rare-Earth Ion-Doped Solid

In a solid-state ensemble of rare-earth ions, we have experimentally generated a photon-echo of a spontaneous emission event, a process referred to as rephased amplified spontaneous emission (RASE). An enabling step for this demonstration was to use a double-Λ energy level structure for the photon-echo, rather than a standard two-pulse/two-level photon echo sequence, such that the single-photon echo is spectrally and spatially distinguishable from the coherent emission that follows imperfect π-pulses.