We report the creation of an ultracold neutral plasma by photoionization of laser-cooled xenon atoms. The charge carrier density is as high as 2 × 10 9 cm −3 , and the temperatures of electrons and ions are as low as 100 mK and 10 µK, respectively. Plasma behavior is evident in the trapping of electrons by the positive ion cloud when the Debye screening length becomes smaller than the size of the sample. We produce plasmas with parameters such that both electrons and ions are strongly coupled.The study of ionized gases in neutral plasma physics spans temperatures ranging from 10 16 K in the magnetosphere of a pulsar to 300 K in the earth's ionosphere [1]. At lower temperatures the properties of plasmas are expected to differ significantly. For instance, three-body recombination which is prevalent in high temperature plasmas, should be suppressed [2]. If the thermal energy of the particles is less than the Coulomb interaction energy, the plasma becomes strongly coupled, and the usual hydrodynamic equations of motion and collective mode dispersion relations are no longer valid [3]. Strongly coupled plasmas are difficult to produce in the laboratory and only a handful of examples exist [4], but such plasmas do occur naturally in astrophysical systems.In this work we create an ultracold neutral plasma with an electron temperature as low as T e = 100 mK, an ion temperature as low as T i = 10 µK, and densities as high as n = 2×10 9 cm −3 . We obtain this novel plasma by photoionization of laser-cooled xenon atoms. Within the experimentally accessible ranges of temperatures and densities both components can be simultaneously strongly coupled. A simple model describes the evolution of the plasma in terms of the competition between the kinetic energy of the electrons and the Coulomb attraction between electrons and ions. A numerical calculation accurately reproduces the data.Photoionization and laser-cooling have been used before in plasma experiments. Photoionization in a 600 K Cs vapor cell produced a plasma with T e ≥ 2000 K [5], and a strongly coupled non-neutral plasma was created by laser-cooling magnetically trapped Be + ions [6]. A plasma is often defined as an ionized gas in which the charged particles exhibit collective effects [7]. The length scale which divides individual particle behavior and collective behavior is the Debye screening length λ D . It is the distance over which an electric field is screened by redistribution of electrons in the plasma, and is given by λ D = ǫ 0 k B T e /e 2 n. Here, ǫ 0 is the electric permittivity of vacuum, k B is the Boltzmann constant, and e is the elementary charge. An ionized gas is not a plasma unless the Debye length is smaller than the size of the system [7]. In our experiment, the Debye length can be as low as 500 nm, while the size of the sample is σ ≈ 200 µm. The condition λ D < σ for creating a plasma is thus easily fulfilled.The atomic system we use is metastable xenon in the 6s [3/2] 2 state. This state has a lifetime of 43 s [8] and can be treated as the groun...

Atoms interact with each other through the electromagnetic field, creating collective states that can radiate faster or slower than a single atom, i.e., super- and sub-radiance. When the field is confined to one dimension it enables infinite-range atom–atom interactions. Here we present the first report of infinite-range interactions between macroscopically separated atomic dipoles mediated by an optical waveguide. We use cold 87Rb atoms in the vicinity of a single-mode optical nanofiber (ONF) that coherently exchange evanescently coupled photons through the ONF mode. In particular, we observe super-radiance of a few atoms separated by hundreds of resonant wavelengths. The same platform allows us to measure sub-radiance, a rarely observed effect, presenting a unique tool for quantum optics. This result constitutes a proof of principle for collective behavior of macroscopically delocalized atomic states, a crucial element for new proposals in quantum information and many-body physics.

We report measurements in cavity QED of a wave-particle correlation function which records the conditional time evolution of the field of a fraction of a photon. Detection of a photon prepares a state of well-defined phase that evolves back to equilibrium via a damped vacuum Rabi oscillation. We record the regression of the field amplitude. The recorded correlation function is nonclassical and provides an efficiency independent path to the spectrum of squeezing. Nonclassicality is observed even when the intensity fluctuations are classical.

We use time-correlated single-photon counting techniques on a sample of 210 Fr atoms confined and cooled in a magneto-optical trap to measure the lifetimes of the 9S 1/2 , 8P 3/2 , and 8P 1/2 excited levels. We populate the 9S 1/2 level by two-photon resonant excitation through the 7P 1/2 level. The direct measurement of the 9S 1/2 decay through the 7P 3/2 level at 851 nm gives a lifetime of 107.53± 0.90 ns. We observe the decay of the 9S 1/2 level through the 8P 3/2 level at 423 nm and the 8P 1/2 level at 433 nm down to the 7S 1/2 ground level, and indirectly determine the lifetimes of these to be 83.5± 1.5 ns and 149.3± 3.5 ns, respectively.

Conditional homodyne detection is proposed as an extension of the intensity correlation technique introduced by Hanbury-Brown and Twiss [Nature (London) 177, 27 (1956)]. It detects giant quadrature amplitude fluctuations for weakly squeezed light, violating a classical bound by orders of magnitude. Fluctuations of both quadrature amplitudes are anomalously large. The squeezed quadrature also exhibits an anomalous phase.

The second-order intensity correlation function of light transmitted out of a cavity QED system exhibits the nonclassical features and dynamics of the atom-field interaction. We present measurements of the intensity correlation to examine the size of the nonclassical features and the dependence on driving intensity, detuning, and the strength of the atom-field coupling. We use a model that takes into account experimental conditions to achieve a quantitative agreement with the observations. PACS number͑s͒: 42.50.Dv, 42.50.Ct, 32.80.Ϫtwhere is the transition dipole moment, is the transition frequency, and V is the cavity mode volume. There are three PHYSICAL REVIEW A, VOLUME 61, 053821

δ Δ ^F IG. 1: (a) Schematics of the interface: Atoms (sphere), in a 1D lattice of the length L, are electrically (magnetically) coupled to light in the nanofiber (the superconducting waveguide), respectively. The quantum microwave (optical) field with Rabi frequencyÊM (Êo) is manipulated using a classical control radio-frequency (optical) field with Rabi frequency ΩM (Ωo), respectively. Trapping lights are not shown in the figure. (b) The quantum (ÊM) and control (ΩM) electromagnetic fields arrive while the atomic system is in the ground state. (c) The quantum field is stored as an atomic spin excitation (S(z)). (d) Internal level structure of a 87 Rb atom and transitions induced by the four electromagnetic fields. δ, ∆2 are two-photon and one-photon detunings, respectively. (e) Dimensions of an example LC resonator. (f) Magnetic field profile viewed from the top, lighter colors show higher fields.level atoms [4, 5], based on electric-dipole coupling in a Λ-system, allow for efficient storage and retrieval of optical photons into atomic excitations from an ensemble of atoms. We adapt this approach to also store and retrieve MW photons. We investigate the effect of finite bandwidth of MW photons on the storage-retrieval process arXiv:1110.3537v2 [quant-ph]

We present a procedure for reproducibly fabricating ultrahigh transmission optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode transmissions of 99.95 ± 0.02 %, which represents a loss from tapering of 2.6 × 10 −5 dB/mm when normalized to the entire stretch. When controllably launching the next family of higher-order modes on a fiber with 195 mm stretch, we achieve a transmission of 97.8 ± 2.8%, which has a loss from tapering of 5.0 × 10 −4 dB/mm when normalized to the entire stretch. Our pulling and transfer procedures allow us to fabricate optical nanofibers that transmit more than 400 mW in high vacuum conditions. These results, published as parameters in our previous work, present an improvement of two orders of magnitude less loss for the fundamental mode and an increase in transmission of more than 300% for higher-order modes, when following the protocols detailed in this paper. We extract from the transmission during the pull, the only reported spectrogram of a fundamental mode launch that does not include excitation to asymmetric modes; in stark contrast to a pull in which our cleaning protocol is not followed. These results depend critically on the pre-pull cleanliness and when properly following our pulling protocols are in excellent agreement with simulations.