Deterministic Generation of Single Photons from One Atom Trapped in a Cavity

Abstract

EXPERIMENTAL DETAILSOur experimental setup is depicted by the simple drawing in Fig. 1A of the manuscript, with many of the technical aspects described in more detail in Refs.[S1, S2]. After releasing a cloud of atoms from a magnetooptical trap (MOT) above the cavity, transverse cooling beams illuminate the cavity region, at which point an atom can be loaded into the intracavity far-off resonance trap (FORT), which is matched to a standingwave, TEM 00 mode along the cavity axis. The trap depth is U 0 /k B = 2.3 mK (47 MHz), and because its wavelength is λ F = 935.6 nm, the potential for the atomic center-of-mass motion is only weakly dependent on the atom's internal state [S2]. The cavity length is actively stabilized with an auxiliary laser at wavelength λ C = 835.8 nm that does not interfere with the trapping or the cQED interactions. Relevant cavity parameters are length l 0 = 42.2 µm, waist w 0 = 23.6 µm, and finesse F = 4.2 × 10 5 at 852 nm. For our system, the Rabi frequency 2g 0 for a single quantum of excitation is given by g 0 /2π = 16 MHz, where g 0 is based upon the reduced dipole moment for the 6S 1/2 , F = 4 ↔ 6P 3/2 , F = 3 transition in atomic Cs (Fig 1B). The amplitude decay rates (κ, γ) due to cavity losses and atomic spontaneous emission are κ/2π = 4.2 MHz, and γ/2π = 2.6 MHz. Since g 0 (κ, γ), strong coupling is achieved, resulting in critical photon and atom numbers n 0 ≡ γ 2 /(2gWith an atom loaded into the intracavity FORT, our protocol for the generation of single-photon pulses consists in illuminating the atom with a sequence of laser pulses according to the timing diagram shown in Fig. 1(c) of the manuscript. Within each trial, the first pulse Ω 3 (t) contains light tuned 10 MHz blue of F = 3 → F = 3 , which initiates the adiabatic transfer F = 3 → 4 between the ground hyperfine levels, with the emission of a photon into the cavity mode. This transformation is principally accomplished via "dark" eigenstates of the atom-cavity system, with no contribution from the excited level F = 3 , and hence with a concomitant reduction of fluorescent loss [S3, S4, S5]. The second pulse Ω 4 (t) is tuned 17 MHz blue of F = 4 → F = 4 and recycles the atom back to the F = 3 ground state through spontaneous decay F = 4 → F = 3. Each Ω 3,4 field consists of two orthogonal pairs of counter-propagating beams in a σ + −σ − configuration. The detuning between the 3 → 4 transition at ω 43 and the cavity resonance ω C is ∆ CA ≡ ω C − ω 43 = 2π × 9 MHz [S6].We now provide some additional details on the optical path from the cavity to the detectors. After emerging from the vacuum chamber window, the path includes a polarizing beam splitter (PBS), several dichroic mirrors and two interference filters. The light is next coupled into a single-mode fiber, and then split using a 50/50 fiber coupler. The two output fibers of the coupler are connected to fiber-coupled avalanche photodiodes (APD), labelled D A and D B . LOSSES AND EFFICIENCIESPhotons generated in the cavity are subject to various types of loss along thei...

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