Observation of dressed states of distant atoms with delocalized photons in coupled-cavities quantum electrodynamics

Photon transport enhancement through a coupled-cavity QED system with dynamic modulation

We investigate photonic transport through fiber optical cavities under tunable fast modulation, which is induced by modulating atom-cavity coupling in a cavity quantum electrodynamics (CQED) system. The modulation bandwidth exceeds the timescales of all other system processes, such as cavity decay and atom-cavity coupling, and allows control of the dynamics of photonic transport through the cavity array. The transmission as a function of the modulation frequency clearly shows enhancement peaks in single cavity and two coupled-cavity cases. In particular, in the coupled-cavity case, the position of the enhancement peak is shifted due to the delocalized cavity field in the coupled system.

Enantio-detection via cavity-assisted three-photon processes

We propose a method for enantio-detection of chiral molecules based on a cavity-molecule system, where the left- and right-handed molecules are coupled with a cavity and two classical light fields to form cyclic three-level models. Via the cavity-assisted three-photon processes based on the cyclic three-level model, photons are generated continuously in the cavity even in the absence of external driving to the cavity. However, the photonic fields generated from the three-photon processes of left- and right-handed molecules differ with the phase difference π according to the inherent properties of electric-dipole transition moments of enantiomers. This provides a potential way to detect the enantiomeric excess of chiral mixture by monitoring the output field of the cavity.

Characterization of suspended membrane waveguides towards a photonic atom trap integrated platform

We demonstrate an optical waveguide device, capable of supporting the high, in-vacuum, optical power necessary for trapping a single atom or a cold atom ensemble with evanescent fields. Our photonic integrated platform, with suspended membrane waveguides, successfully manages optical powers of 6 mW (500 μm span) to nearly 30 mW (125 μm span) over an un-tethered waveguide span. This platform is compatible with laser cooling and magneto-optical traps (MOTs) in the vicinity of the suspended waveguide, called the membrane MOT and the needle MOT, a key ingredient for efficient trap loading. We evaluate two novel designs that explore critical thermal management features that enable this large power handling. This work represents a significant step toward an integrated platform for coupling neutral atom quantum systems to photonic and electronic integrated circuits on silicon.

Demonstration of a MOT in a sub-millimeter membrane hole

We demonstrate the generation of a cold-atom ensemble within a sub-millimeter diameter hole in a transparent membrane, a so-called “membrane MOT”. With a sub-Doppler cooling process, the atoms trapped by the membrane MOT are cooled down to 10 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μK. The atom number inside the unbridged/bridged membrane hole is about \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10^4$$\end{document}104 to \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10^5$$\end{document}105, and the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1/e^2$$\end{document}1/e2-diameter of the MOT cloud is about 180 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μm for a 400 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu$$\end{document}μm-diameter membrane hole. Such a membrane device can, in principle, efficiently load cold atoms into the evanescent-field optical trap generated by the suspended membrane waveguide for strong atom-light interaction and provide the capability of sufficient heat dissipation at the waveguide. This represents a key step toward the photonic atom trap integrated platform (ATIP).

High-efficiency coupling of single quantum emitters into hole-tailored nanofibers

We propose a scheme to enhance the coupling efficiency of photons from a single quantum emitter into a hole-tailored nanofiber. The single quantum emitter is positioned inside a circular hole etched along the radial axis of the nanofiber. The coupling efficiency can be effectively enhanced and is twice as high as the case in which only an intact nanofiber without the hole is used. The effective enhancement independent of a cavity can avoid the selection of a single emitter for the specific wavelength, which means a broad operating wavelength range. Numerical simulations are performed to optimize the coupling efficiency by setting appropriate diameters of the nanofiber and the hole. The simulation results show that the coupling efficiency can reach 62.8% when the single quantum emitter with azimuthal polarization (x direction) is at a position 200 nm from the middle of the hole along the hole-axial direction. The diameters of the nanofiber and the hole are 800 nm and 400 nm, respectively, while the wavelength of the single quantum emitter is 852 nm. Hole-tailored nanofibers have a simple configuration and are easy to fabricate and integrate with other micro/nanophotonic structures; this fiber structure has wide application prospects in quantum information processing and quantum precision measurement.

Optical properties of a waveguide-mediated chain of randomly positioned atoms

We theoretically study the optical properties of an ensemble of two-level atoms coupled to a one-dimensional waveguide. In our model, the atoms are randomly located in the lattice sites along the one-dimensional waveguide. The results reveal that the optical transport properties of the atomic ensemble are influenced by the lattice constant and the filling factor of the lattice sites. We also focus on the atomic mirror configuration and quantify the effect of the inhomogeneous broadening in atomic resonant transition on the scattering spectrum. Furthermore, we find that initial bunching and persistent quantum beats appear in photon-photon correlation function of the transmitted field, which are significantly changed by the filling factor of the lattice sites. With great progress to interface quantum emitters with nanophotonics, our results should be experimentally realizable in the near future.

Atoms in separated resonators can jointly absorb a single photon

The coherent nonlinear process where a single photon simultaneously excites two or more two-level systems (qubits) in a single-mode resonator has recently been theoretically predicted. Here we explore the case where the two qubits are placed in different resonators in an array of two or three weakly coupled resonators. Investigating different setups and excitation schemes, we show that this process can still occur with a probability approaching one under specific conditions. The obtained results provide interesting insights into subtle causality issues underlying the simultaneous excitation processes of qubits placed in different resonators.

Ultra-low-loss nanofiber Fabry-Perot cavities optimized for cavity quantum electrodynamics

We demonstrate the fabrication of ultra-low-loss, all-fiber Fabry-Perot cavities that contain a nanofiber section, optimized for cavity quantum electrodynamics. By continuously monitoring the finesse and fiber radius during the fabrication of a nanofiber between two fiber Bragg gratings, we were able to precisely evaluate taper transmission as a function of radius. The resulting cavities have an internal round-trip loss of only 0.31% at a nanofiber waist radius of 207 nm, with a total finesse of 1380, and a maximum expected internal cooperativity of ∼1050 for a cesium atom on the nanofiber surface. Our ability to fabricate such high-finesse nanofiber cavities may open the door for the realization of high-fidelity scalable quantum networks.

Light-mediated strong coupling between a mechanical oscillator and atomic spins 1 meter apart

Engineering strong interactions between quantum systems is essential for many phenomena of quantum physics and technology. Typically, strong coupling relies on short-range forces or on placing the systems in high-quality electromagnetic resonators, which restricts the range of the coupling to small distances. We used a free-space laser beam to strongly couple a collective atomic spin and a micromechanical membrane over a distance of 1 meter in a room-temperature environment. The coupling is highly tunable and allows the observation of normal-mode splitting, coherent energy exchange oscillations, two-mode thermal noise squeezing, and dissipative coupling. Our approach to engineering coherent long-distance interactions with light makes it possible to couple very different systems in a modular way, opening up a range of opportunities for quantum control and coherent feedback networks.

Non-Markovian Collective Emission from Macroscopically Separated Emitters

We study the collective radiative decay of a system of two two-level emitters coupled to a one-dimensional waveguide in a regime where their separation is comparable to the coherence length of a spontaneously emitted photon. The electromagnetic field propagating in the cavity-like geometry formed by the emitters exerts a retarded backaction on the system leading to strongly non-Markovian dynamics. The collective spontaneous emission rate of the emitters exhibits an enhancement or inhibition beyond the usual Dicke superradiance and subradiance due to self-consistent coherent time-delayed feedback.

Cavity Dark Mode of Distant Coupled Atom-Cavity Systems

We report on a combined experimental and theoretical investigation into the normal modes of an all-fiber coupled cavity-quantum-electrodynamics system. The interaction between atomic ensembles and photons in the same cavities, and that between the photons in these cavities and the photons in the fiber connecting these cavities, generates five nondegenerate normal modes. We demonstrate our ability to excite each normal mode individually. We study particularly the "cavity dark mode," in which the two cavities coupled directly to the atoms do not exhibit photonic excitation. Through the observation of this mode, we demonstrate remote excitation and nonlocal saturation of atoms.