M. D. Lukin

Quantum optics with surface plasmons.

We describe a technique that enables strong, coherent coupling between individual optical emitters and guided plasmon excitations in conducting nanostructures at optical frequencies. We show that under realistic conditions optical emission can be almost entirely directed into the plasmon modes. As an example, we describe an application of this technique involving efficient generation of single photons on demand, in which the plasmon is efficiently outcoupled to a dielectric waveguide.

Nonlinear optics and quantum entanglement of ultra-slow photons

Two light pulses propagating with ultra-slow group velocities in a coherently prepared atomic gas exhibit dissipation-free nonlinear coupling of an unprecedented strength. This enables a single-photon pulse to coherently control or manipulate the quantum state of the other. Processes of this kind result in generation of entangled states of radiation field and open up new prospectives for quantum information processing.

High-temperature superfluidity of fermionic atoms in optical lattices.

Fermionic atoms confined in a potential created by standing wave light can undergo a phase transition to a superfluid state at a dramatically increased transition temperature. Depending upon carefully controlled parameters, a transition to a superfluid state of Cooper pairs, antiferromagnetic states or d-wave pairing states can be induced and probed under realistic experimental conditions. We describe an atomic physics experiment that can provide critical insight into the origin of high-temperature superconductivity in cuprates.

Coupling a Single Trapped Atom to a Nanoscale Optical Cavity

Trapped and Coupled Trapped single atoms are ideal for storing and manipulating quantum information. Thompson et al. (p. 1202, published online 25 April; see the Perspective by Keller) were able to control single atoms interacting coherently with a field mode of a photonic crystal cavity. An optical tweezer was used to trap the single atom, which enabled positioning of the atom in close proximity to the photonic crystal waveguide, coupling the atom to the optical mode of the cavity. Such coupling should prove useful in quantum measurement, sensing, and information processing. A single rubidium atom is positioned in close proximity to an optical cavity so they can interact. [Also see Perspective by Keller] Hybrid quantum devices, in which dissimilar quantum systems are combined in order to attain qualities not available with either system alone, may enable far-reaching control in quantum measurement, sensing, and information processing. A paradigmatic example is trapped ultracold atoms, which offer excellent quantum coherent properties, coupled to nanoscale solid-state systems, which allow for strong interactions. We demonstrate a deterministic interface between a single trapped rubidium atom and a nanoscale photonic crystal cavity. Precise control over the atoms position allows us to probe the cavity near-field with a resolution below the diffraction limit and to observe large atom-photon coupling. This approach may enable the realization of integrated, strongly coupled quantum nano-optical circuits.

Manipulating light pulses via dynamically controlled photonic band gap.

When a resonance associated with electromagnetically induced transparency in an atomic ensemble is modulated by an off-resonant standing light wave, a band of frequencies can appear for which light propagation is forbidden. We show that dynamic control of such a band gap can be used to coherently convert a propagating light pulse into a stationary excitation with nonvanishing photonic component. This can be accomplished with high efficiency and negligible noise even at the level of few-photon quantum fields thereby facilitating possible applications in quantum nonlinear optics and quantum information.

Magnetic field imaging with nitrogen-vacancy ensembles

We demonstrate a method of imaging spatially varying magnetic fields using a thin layer of nitrogen-vacancy (NV) centers at the surface of a diamond chip. Fluorescence emitted by the two-dimensional NV ensemble is detected by a CCD array, from which a vector magnetic field pattern is reconstructed. As a demonstration, ac current is passed through wires placed on the diamond chip surface, and the resulting ac magnetic field patterns are imaged using an echo-based technique with sub-micron resolution over a 140µm◊140µm field of view, giving single-pixel sensitivity 100nT/ p Hz. We discuss ongoing efforts to further improve the sensitivity, as well as potential bioimaging applications such as real-time imaging of activity in functional, cultured networks of neurons.

Coupling of NV Centers to Photonic Crystal Nanobeams in Diamond

The realization of efficient optical interfaces for solid-state atom-like systems is an important problem in quantum science with potential applications in quantum communications and quantum information processing. We describe and demonstrate a technique for coupling single nitrogen vacancy (NV) centers to suspended diamond photonic crystal cavities with quality factors up to 6000. Specifically, we present an enhancement of the NV centers zero-phonon line fluorescence by a factor of ~ 7 in low-temperature measurements.

Quantum control of proximal spins using nanoscale magnetic resonance imaging

Single electron spins have been detected before, but the methods used proved difficult to extend to multi-spin systems. A magnetic resonance imaging technique is now demonstrated that resolves proximal spins in three dimensions with nanometre-scale resolution. In addition to spatial mapping, the approach allows for coherent control of the individual spins.

Nondegenerate Parametric Self-Oscillation via Multiwave Mixing in Coherent Atomic Media

We demonstrate an efficient nonlinear process in which Stokes and anti-Stokes components are generated spontaneously in a Raman-like, near resonant media driven by low power counter-propagating fields. Oscillation of this kind does not require optical cavity and can be viewed as a spontaneous formation of atomic coherence grating. PACS numbers: 42.50.-p;42.65.-k;42.50.Gy Typeset using REVTEX present address: National Institute of Standards and Technology, Boulder, Colorado, 80303 1 Theoretical and experimental work of past few years on atomic coherence and interference has demonstrated a potential to improve significantly the existing nonlinear optical techniques [1]. In the present Letter we demonstrate efficient parametric generation accompanying the spontaneous formation of the coherent superposition states. Specifically, the present work reports the observation of the spontaneous parametric self-oscillation in resonant Raman media. Such generation does not involve optical cavity and appears under remarkably simple circumstances, when two low-power counter-propagating fields interact with the medium. Oscillation manifests itself as Stokes and anti-Stokes components generated with a frequency shift corresponding to that of the Raman transition. As the oscillator goes over threshold, dramatic increase and narrowing of the beat note between the input field and generated components takes place. The principal possibility of mirrorless parametric oscillation with counter-propagating signal and idler fields has been suggested in 1960’s by Harris [2]. The original proposal based on non-degenerate frequency mixing has not been realized up to now due to small values of nonlinearities in available materials and difficulties in achieving phase matching [3]. It is easier to achieve mirrorless oscillation in degenerate four-wave mixing. The possibility of self-oscillation in such interactions has been predicted in [4], and a number of the related effects, such as conical emission or transverse pattern formation have been observed in a vapor driven by very strong, off-resonant counter-propagating laser beams [5]. Workers in the field have also noted the importance of Raman nonlinearities in the early experiments on polarizations instabilities [6]. As compared to the above work the presently reported results utilize atomic coherence gratings [7,8] in a resonant double-Λ atomic system (Fig.1a). Coupling of counterpropagating Stokes and anti-Stokes fields via such a grating appears to be the main physical mechanism resulting in Raman self-oscillation [8]. Similar to several related studies [1,7,9,10] the present work operates in a so-called strong coupling regime in which nonlinearities can not be derived from a usual perturbation expansion. In this regime quantum coherence and interference have a profound influence on nonlinear parametric amplification. For ex-

Mesoscopic molecular ions in Bose-Einstein condensates.

We study the possible formation of large (mesoscopic) molecular ions in an ultracold degenerate bosonic gas doped with charged particles (ions). We show that the polarization potentials produced by the ionic impurities are capable of capturing hundreds of atoms into loosely bound states. We describe the spontaneous formation of these hollow molecular ions via phonon emission and suggest an optical technique for coherent stimulated transitions of condensate atoms into a specific bound state. These results open up new possibilities for manipulating tightly confined ensembles.