We report the demonstration of strong coupling between single Cesium atoms and a high-Q chip-based microresonator.
Our toroidal microresonators are compact, Si chip-based whispering gallery mode resonators that confine light to small
volumes with extremely low losses, and are manufactured in large numbers by standard lithographic techniques.
Combined with the capability to couple efficiently light to and from these microresonators by a tapered optical fiber,
toroidal microresonators offer a promising avenue towards scalable quantum networks. Experimentally, laser cooled Cs
atoms are dropped onto a toroidal microresonator while a probe beam is critically coupled to the cavity mode. When an
atom interacts with the cavity, it modifies the resonance spectrum of the cavity, leading to rejection of some of the probe
light from the cavity, and thus to an increase in the output power. By observing such transit events while systematically
detuning the cavity from the atomic resonance, we determine the maximal accessible single-photon Rabi frequency of
Ω0/2π ≈ (100 ± 24) MHz. This value puts our system in the regime of strong coupling, being significantly larger than the dissipation rates in our system.
We give the detailed study of a scheme to efficiently engineer multi-atom entanglement by detecting the cavity decay through single-photon detectors. The scheme can be used to prepare arbitrary superpositions of multi-atom Dicke states, without the requirements of high-efficiency detection, separate addressing of different atoms, and full localization of the atoms to the Lamb-Dicke limit. We analyze in detail various sources of noise and imperfections in this experimental scheme, and show that the scheme is robust to the dominant sources of noise and realizable with the state of the
We report recent developments in our experiment to teleport light beams by utilizing Einstein-Podolsky-Rosen (EPR) entanglement for continuous quantum variables. We describe details of our experimental apparatus, including the generation of EPR entanglement from squeezed states of light. In addition, we have developed an explicit model for the teleportation of coherent states that includes the effect of diverse loss factors and limited degrees of entanglement, and that enables us to project the possibilities for achieving yet higher fidelities beyond the currently achieved value of 62% with our apparatus. Propects for other teleportation schemes will also be discussed.
Strongly coupled cavity QED systems show great promise for coherent processing of quantum information in the contexts of quantum computing, communication and cryptography. We present here current progress in experiments for which single atoms are strongly coupled to the mode of a high finesse optical resonator.
The Whispering Gallery Modes of fused silica microspheres hold the promise for simultaneous achievement of high Q (> 109) and small mode volumes (<EQ 10-14 m3) necessary for strong coupling in cavity QED. Here we present results for high Q measurements into the NIR along with some progress towards experimental implementation in cavity QED.
A variety of experiments are underway in the Quantum Optics Group at Caltech which investigate the quantum nature of atom-field interactions at the level of individual atoms and quanta. A recent technical advance in support of this research is the observation of cooling and trapping of single neutral cesium atoms in magneto-optical trap. Discrete steps are recorded in the fluorescence signal from the trap and are associated with the arrival and departure of individual trapped atoms. Such a spatially localized sample of a single atom with small kinetic energy is an enabling advance for diverse studies in quantum optics, including the possibility of spectroscopy with squeezed and other forms of nonclassical light and cavity quantum electrodynamics with strong coupling of an atom to the field of an optical cavity.
Frequency doubling and optical parametric oscillation are investigated with potassium niobate in an external resonator. For frequency doubling of 860 nm input, 650 mW of cw blue light around 430 nm has been generated for 1.35 W of infrared input. In a cavity with reduced losses, overall conversion efficiency of up to 70% has been achieved. With regard to parametric oscillation with a 430 nm pump, 100 mW of stable cw emission from the optical parametric oscillator has been obtained for pump power 250 mW. Blue-light induced infrared absorption has been discovered to have significant deleterious effects and to be the principal reason why even higher efficiencies have not been reached.