Strong interactions of single atoms and photons near a dielectric boundary (original) (raw)
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Strong interaction between light and a single trapped atom without a cavity
Many quantum information processing protocols require efficient transfer of quantum information from a flying photon to a stationary quantum system. To transfer information, a photon must first be absorbed by the quantum system. A flying photon can be absorbed by an atom residing in a high-finesse cavity with a probability close to unity. However, it is unclear whether a photon can be absorbed effectively by an atom in a free space. Here, we report on an observation of substantial extinction of a light beam by a single 87 Rb atom through focusing light to a small spot with a single lens. The measured extinction values are not influenced by interference-related effects, and thus can be compared directly to the predictions by existing free-space photon-atom coupling models. Our result opens a new perspective on processing quantum information carried by light using atoms, and is important for experiments that require strong absorption of single photons by an atom in free space.
Observation of strong coupling between one atom and a monolithic microresonator
Nature, 2006
Over the past decade, strong interactions of light and matter at the single-photon level have enabled a wide set of scientific advances in quantum optics and quantum information science. This work has been performed principally within the setting of cavity quantum electrodynamics 1-4 with diverse physical systems 5 , including single atoms in Fabry-Perot resonators 1,6 , quantum dots coupled to micropillars and photonic bandgap cavities and Cooper pairs interacting with superconducting resonators 9,10 . Experiments with single, localized atoms have been at the forefront of these advances 11-15 with the use of optical resonators in high-finesse Fabry-Perot configurations . As a result of the extreme technical challenges involved in further improving the multilayer dielectric mirror coatings 17 of these resonators and in scaling to large numbers of devices, there has been increased interest in the development of alternative microcavity systems 5 . Here we show strong coupling between individual caesium atoms and the fields of a high-quality toroidal microresonator. From observations of transit events for single atoms falling through the resonator's evanescent field, we determine the coherent coupling rate for interactions near the surface of the resonator. We develop a theoretical model to quantify our observations, demonstrating that strong coupling is achieved, with the rate of coherent coupling exceeding the dissipative rates of the atom and the cavity. Our work opens the way for investigations of optical processes with single atoms and photons in lithographically fabricated microresonators. Applications include the implementation of quantum networks 18,19 , scalable quantum logic with photons 20 , and quantum information processing on atom chips 21 .
Single Atom as a Mirror of an Optical Cavity
Physical Review Letters, 2011
At the microscopic level, light-matter interactions are described by quantum electrodynamics (QED), a theory that often defies our classical interpretations and still asks for close experimental investigations. Improvements in the research of atomic trapping and laser cooling now allow this theory to be tested with an unprecedented level of precision . Here, by tightly focussing a laser field onto a cold ion trapped in front of a distant dielectric mirror, we observe a QED effect whereby the ion behaves as the optical mirror of a Fabry-Pérot cavity. The amplitude of the laser field is altered due to a modification of the electromagnetic mode structure around the atom in a novel regime in which the laser intensity is already changed by the atom alone. Our investigations should find applications in quantum communication using single atoms and single photons in free space.
Arrays of waveguide-coupled optical cavities that interact strongly with atoms
New Journal of Physics, 2011
We describe a realistic scheme for coupling atoms or other quantum emitters with an array of coupled optical cavities. We consider open Fabry-Perot microcavities coupled to the emitters. Our central innovation is to connect the microcavities to waveguide resonators, which are in turn evanescently coupled to each other on a photonic chip to form a coupled cavity chain. In this paper, we describe the components, their technical limitations and the factors that need to be determined experimentally. This provides the basis for a detailed theoretical analysis of two possible experiments to realize quantum squeezing and controlled quantum dynamics. We close with an outline of more advanced applications.
Controlled generation of single photons from a strongly coupled atom-cavity system
Applied Physics B, 1999
We propose a new method for the generation of single photons. Our scheme will lead to the emission of one photon into a single mode of the radiation field in response to a trigger event. This photon is emitted from an atom strongly coupled to a high-finesse optical cavity, and the trigger is a classical light pulse. The device combines cavity-QED with an adiabatic transfer technique. We simulate this process numerically and show that it is possible to control the temporal behaviour of the photon emission probability by the shape and the detuning of the trigger pulse. An extension of the scheme with a reloading mechanism will allow one to emit a bit-stream of photons at a given rate.
The Atom-Cavity Microscope: Single Atoms Bound in Orbit by Single Photons
Science, 2000
The motion of individual cesium atoms trapped inside an optical resonator is revealed with the atom-cavity microscope (ACM). A single atom moving within the resonator generates large variations in the transmission of a weak probe laser, which are recorded in real time. An inversion algorithm then allows individual atom trajectories to be reconstructed from the record of cavity transmission and reveals single atoms bound in orbit by the mechanical forces associated with single photons. In these initial experiments, the ACM yields 2-micrometer spatial resolution in a 10-microsecond time interval. Over the duration of the observation, the sensitivity is near the standard quantum limit for sensing the motion of a cesium atom.
How to trap photons? Storing single-photon quantum states in collective atomic excitations
Optics Communications, 2000
We s h o w that it is possible to \store" quantum states of single-photon elds by mapping them onto collective meta-stable states of an optically dense, coherently driven medium inside an optical resonator. An adiabatic technique is suggested which a l l o ws to transfer non-classical correlations from traveling-wave single-photon wave-packets into atomic states and vise versa with nearly 100% e ciency. I n c o n trast to previous approaches involving single atoms, the present t e c hnique does not require the strong coupling regime corresponding to high-Q micro-cavities. Instead, intracavity Electromagnetically Induced Transparency is used to achieve a strong coupling between the cavity mode and the atoms.
Strong atom–field coupling for Bose–Einstein condensates in an optical cavity on a chip
Nature, 2007
An optical cavity enhances the interaction between atoms and light, and the rate of coherent atom-photon coupling can be made larger than all decoherence rates of the system. For single atoms, this "strong coupling regime" of cavity quantum electrodynamics 1,2 (cQED) has been the subject of spectacular experimental advances, and great efforts have been made to control the coupling rate by trapping 3,4 and cooling the atom 5,6 towards the motional ground state, which has been achieved in one dimension so far 5 . For N atoms, the three-dimensional ground state of motion is routinely achieved in atomic Bose-Einstein condensates (BECs) 7 , but although first experiments combining BECs and optical cavities have been reported recently 8,9 , coupling BECs to strong-coupling cavities has remained an elusive goal. Here we report such an experiment, which is made possible by combining a new type of fibre-based cavity 10 with atom chip technology 11 . This allows single-atom cQED experiments with a simplified setup and realizes the new situation of N atoms in a cavity each of which is identically and strongly coupled to the cavity mode 12 . Moreover, the BEC can be positioned deterministically anywhere within the cavity and localized entirely within a single antinode of the standing-wave cavity field. This gives rise to a controlled, tunable coupling rate, as we confirm experimentally. We study the heating rate caused by a cavity transmission measurement as a function of the coupling rate and find no measurable heating for strongly coupled BECs. The spectrum of the coupled atoms-cavity system, which we map out over a wide range of atom numbers and cavity-atom detunings, shows vacuum Rabi splittings exceeding 20 gigahertz, as well as an unpredicted additional splitting which we attribute to the atomic hyperfine structure. The system is suitable as a light-matter quantum interface for quantum information 13 .
Applied Physics B
The paradigm of cavity QED is a two-level emitter interacting with a high-quality factor single-mode optical resonator. The hybridization of the emitter and photon wave functions mandates large vacuum Rabi frequencies and long coherence times; features that so far have been successfully realized with trapped cold atoms and ions, and localized solid-state quantum emitters such as superconducting circuits, quantum dots, and color centers Reiserer and Rempe (Rev Modern Phys 87:1379, 2015), Faraon et al. (Phys Rev 81:033838, 2010). Thermal atoms, on the other hand, provide us with a dense emitter ensemble and in comparison to the cold systems are more compatible with integration, hence enabling large-scale quantum systems. However, their thermal motion and large transit-time broadening is a major bottleneck that has to be circumvented. A promising remedy could benefit from the highly controllable and tunable electromagnetic fields of a nano-photonic cavity with strong local electric-field enhancements. Utilizing this feature, here we investigate the interaction between fast moving thermal atoms and a nano-beam photonic crystal cavity (PCC) with large quality factor and small mode volume. Through fully quantum mechanical calculations, including Casimir-Polder potential (i.e. the effect of the surface on radiation properties of an atom), we show, when designed properly, the achievable coupling between the flying atom and the cavity photon would be strong enough to lead to quantum interference effects in spite of short interaction times. In addition, the time-resolved detection of different trajectories can be used to identify single and multiple atom counts. This probabilistic approach will find applications in cavity QED studies in dense atomic media and paves the way towards realizing large-scale, room-temperature macroscopic quantum systems aimed at out of the lab quantum devices.
Efficient routing of single photons by one atom and a microtoroidal cavity
Physical review letters, 2009
Single photons from a coherent input are efficiently redirected to a separate output by way of a fiber-coupled microtoroidal cavity interacting with individual Cesium atoms. By operating in an overcoupled regime for the input-output to a tapered fiber, our system functions as a quantum router with high efficiency for photon sorting. Single photons are reflected and excess photons transmitted, as confirmed by observations of photon antibunching (bunching) for the reflected (transmitted) light. Our photon router is robust against large variations of atomic position and input power, with the observed photon antibunching persisting for intracavity photon number 0.03 n 0.7.