On the impossibility of faithfully storing single-photons with the three-pulse photon echo

The three-pulse photon echo is a well-known technique to store intense light pulses in an inhomogeneously broadened atomic ensemble. This protocol is attractive because it is relatively simple and it is well suited for the storage of multiple temporal modes. Furthermore, it offers very long storage times, greater than the phase relaxation time. Here, we consider the three-pulse photon echo in both two- and three-level systems as a potential technique for the storage of light at the single-photon level. By explicit calculations, we show that the ratio between the echo signal corresponding to a single-photon input and the noise is smaller than one. This severely limits the achievable fidelity of the quantum state storage, making the three-pulse photon echo unsuitable for single-photon quantum memory.Comment: 6 pages, 4 figure

Time gating of heralded single photons for atomic memories

We demonstrate a method for time gating the standard heralded continuous- wave (cw) spontaneous parametric down-converted (SPDC) single photon source by using pulsed pumping of the optical parametric oscillator (OPO) below threshold. The narrow bandwidth, high purity, high spectral brightness and the pseudo-deterministic character make the source highly suitable for light-atom interfaces with atomic memories.Comment: Accepted for publication in Optics Letter

Broadband stimulated four-wave parametric conversion on a tantalum pentoxide photonic chip

We exploit the large third order nonlinear susceptibility (?(3) or “Chi 3”) of tantalum pentoxide (Ta2O5) planar waveguides and realize broadband optical parametric conversion on-chip. We use a co-linear pump-probe configuration and observe stimulated four wave parametric conversion when seeding either in the visible or the infrared. Pumping at 800 nm we observe parametric conversion over a broad spectral range with the parametric idler output spanning from 1200 nm to 1600 nm in infrared wavelengths and from 555 nm to 600 nm in visible wavelengths. Our demonstration of on-chip stimulated four wave parametric conversion introduces Ta2O5 as a novel material for broadband integrated nonlinear photonic circuit applications

Coherent Control of Stationary Light Pulses

We present a detailed analysis of the recently demonstrated technique to generate quasi-stationary pulses of light [M. Bajcsy {\it et al.}, Nature (London) \textbf{426}, 638 (2003)] based on electromagnetically induced transparency. We show that the use of counter-propagating control fields to retrieve a light pulse, previously stored in a collective atomic Raman excitation, leads to quasi-stationary light field that undergoes a slow diffusive spread. The underlying physics of this process is identified as pulse matching of probe and control fields. We then show that spatially modulated control-field amplitudes allow us to coherently manipulate and compress the spatial shape of the stationary light pulse. These techniques can provide valuable tools for quantum nonlinear optics and quantum information processing.Comment: 27 pages, 10 figure

Low-frequency vacuum squeezing via polarization self-rotation in Rb vapor

We observed squeezed vacuum light at 795 nm in 87Rb vapor via resonant polarization self-rotation, and report noise sidebands suppression of ~1 dB below shot noise level spanning from acoustic (30 kHz) to MHz frequencies. This is the first demonstration of sub-MHz quadrature vacuum squeezing in atomic systems. The spectral range of observed squeezing matches well typical bandwidths of electromagnetically induced transparency (EIT) resonances, making this simple technique for generation of optical fields with non-classical statistics at atomic transitions wavelengths attractive for EIT-based quantum information protocols applications.Comment: 4 pages, 3 figure

Improving single-photon sources with Stark tuning

We investigate the use of the Stark shift in atomlike systems in order to control the interaction with a high-Q/V microcavity. By applying a Stark shift pulse to a single atomlike system, in order to affect and control its detuning from a cavity resonance, the cavity QED interaction can be carefully controlled so as to allow stochastic pumping of the emitting state without causing random timing jitter in the output photon. Using a quantum trajectory approach, we conduct simulations that show this technique is capable of producing indistinguishable single photons that exhibit complete Hong-Ou-Mandel interference. Furthermore, Stark tuning control allows for the generation of arbitrary pulse envelopes. We demonstrate this by showing that a simple asymmetric Stark shifting pulse can lead to the emission of symmetric Gaussian single-photon pulse envelopes, rather than the usual exponential decay. These Gaussian pulses also exhibit complete Hong-Ou-Mandel interference. The use of Stark shifting in solid-state systems could ultimately provide the cheap miniature high quality single-photon sources that are currently required for applications such as all-optical quantum computing

Light storage protocols in Tm:YAG

We present two quantum memory protocols for solids: A stopped light approach based on spectral hole burning and the storage in an atomic frequency comb. These procedures are well adapted to the rare-earth ion doped crystals. We carefully clarify the critical steps of both. On one side, we show that the slowing-down due to hole-burning is sufficient to produce a complete mapping of field into the atomic system. On the other side, we explain the storage and retrieval mechanism of the Atomic Frequency Comb protocol. This two important stages are implemented experimentally in Tm$^{3+}$- doped yttrium-aluminum-garnet crystal

Runaway evaporation for optically dressed atoms

Forced evaporative cooling in a far-off-resonance optical dipole trap is proved to be an efficient method to produce fermionic- or bosonic-degenerated gases. However in most of the experiences, the reduction of the potential height occurs with a diminution of the collision elastic rate. Taking advantage of a long-living excited state, like in two-electron atoms, I propose a new scheme, based on an optical knife, where the forced evaporation can be driven independently of the trap confinement. In this context, the runaway regime might be achieved leading to a substantial improvement of the cooling efficiency. The comparison with the different methods for forced evaporation is discussed in the presence or not of three-body recombination losses