Large Bragg Reflection from One-Dimensional Chains of Trapped Atoms Near a Nanoscale Waveguide

Abstract

We report experimental observations of a large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period nearly commensurate with the resonant wavelength, we observe a reflectance of up to 75% for the guided mode. Each atom behaves as a partially reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum network capabilities and the study of many-body effects emerging from long-range interactions. DOI: 10.1103/PhysRevLett.117.133603 In recent years, the coupling of one-dimensional bosonic waveguides and atoms, either real or artificial, has raised a large interest [1][2][3]. Beyond the remarkable ability to couple a single emitter to a guided mode [3], the 1D reservoir would also enable the exploration and eventual engineering of photon-mediated long-range interactions between multiple qubits, a challenging prospect in free-space geometries. This emerging field of waveguide quantum electrodynamics promises unique applications to quantum networks, quantum nonlinear optics, and quantum simulation [4][5][6].In this context, progress has been reported on various fronts. In the microwave regime, the coupling of superconducting qubits to a one-dimensional transmission line provides a versatile platform to study such photon-mediated interactions [2]. At optical frequencies, recent experimental advances include the development of 1D nanoscale dielectric waveguides coupled to cold atoms trapped in the vicinity [7][8][9]. In these experiments, tight transverse confinement of the electric field achieves an effective mode area comparable to the atomic cross section and thereby a strong atom-photon interaction in a single-pass configuration [10].Coupling of atom arrays to 1D waveguides could lead to a variety of remarkable cooperative phenomena. This coupling can strongly modify the photon transport properties [11][12][13], resulting for instance in sub-and superradiant decays as recently observed for two coupled atoms [14]. It can also lead to photonic band gaps and provide atomic Bragg mirrors, with envisioned applications to integrated cavity QED [15][16][17]. This setting is as well at the basis of a recently proposed deterministic state engineering protocol [18] and constitutes the building block of chiral spin networks in which the emission into the left-and rightpropagating modes is asymmetric [19]. Moreover, strong optomechanical couplings resulting from photon-mediated forces can give rise to rich spatial atomic configurations, including self-organization [20,21].Optical nanofibers offer a promising platform for exploring t...

Optical Nanofibers

“…There is a revival of the reflectivity about 4 µs after the structure pulse, showing a brief re-phasing of some of the pumped atoms oscillating in the trap. Corzo et al (2016) also report Bragg reflection from atoms trapped on a nanofiber. By using an optical lattice with a period nearly commensurate with the resonant wavelength, realized by a pair of close-to-resonance red-detuned counterpropagating beams, they observe a reflectance of up to 75%.…”

“…1 (not to scale), are another example of this kind of structure. It has been demonstrated that ONFs provide an excellent platform to interface trapped atoms to the evanescent field of the mode around a nanometer-size waist region ; Goban et al (2012); Béguin et al (2014); Lee et al (2015); Kato and Aoki (2015); Corzo et al (2016). We review the platform of ONFs with atoms and their implications and applications for quantum physics.…”

“…Typical trapping schemes allow trap depths of fractions of a milliKelvin located a few hundred nanometers from the fiber ; Goban et al (2012); Béguin et al (2014); Lee et al (2015); Kato and Aoki (2015); Corzo et al (2016)). Trapping lifetimes of tens of milliseconds and coherence times of ∼ 600 µs Reitz et al (2013) have been obtained and formation of a one-dimensional lattice along the nanofiber waist has also been demonstrated.…”

3-D near-field imaging of guided modes in nanophotonic waveguides

“…Such lightmatter interfaces have enabled a number of advancements in sensing and quantum information science. For example, ultracold atoms have been trapped and manipulated in evanescent fields of single-mode optical nanofibers for single-photon switches and ultralow power nonlinear optics [1][2][3][4][5]. The strength of the atom-photon interaction depends critically on the waveguide dimensions, and optimization of the light-matter interaction requires exquisite control of the evanescent field by tailoring the precise geometry of the waveguide [6,7].…”

Modal interference in optical nanofibers for sub-Angstrom radius sensitivity

“…These waveguides have enabled several advances in quantum information technologies, including optical switches [8] and atom-mediated optical isolators [9,10], but have also facilitated fundamental experiments in nonlinear atom-light interactions [11], atom-number-resolving detection [12], electromagnetically induced transparency [13][14][15][16], and Bragg reflection from atoms [17,18].…”