We report a source of free electron pulses based on field emission tip irradiated by low-power femtosecond laser. The are shorter than 70 fs and originate from with an area diameter down to 2 nm. Depending the operating regime we observe either photofield or optical up 200 electrons per pulse at repetition rate 1 GHz. This pulsed emitter, triggered oscillator, could serve as efficient for time-resolved interferometry, nanometric imaging synchrotrons.

We study the emergence of collective scattering in presence dipole-dipole interactions when we illuminate a cold cloud rubidium atoms with near-resonant and weak intensity laser. The size atomic sample is comparable to wavelength light. When gradually increase atom number from 1 450, observe broadening line, small red shift and, consistently these, strong suppression scattered light respect noninteracting case. Numerical simulations, which include internal level structure, agree data.

Over five years, we have compared the hyperfine frequencies of $^{133}\mathrm{C}\mathrm{s}$ and $^{87}\mathrm{R}\mathrm{b}$ atoms in their electronic ground state using several laser-cooled atomic fountains with an accuracy $\ensuremath{\sim}{10}^{\ensuremath{-}15}$. These measurements set a stringent upper bound to possible fractional time variation ratio between two frequencies:...

By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant light pulses, we created efficient triggered source of single photons well-defined polarization. The measured intensity correlation the emitted pulses exhibits almost perfect antibunching. Such high-rate, fully controlled single-photon has many potential applications for quantum information processing.

We investigate experimentally the energy distribution of a single $^{87}\mathrm{Rb}$ atom trapped in strongly focused dipole trap under various cooling regimes. Using two different methods to measure mean atom, we show that radiatively cooled is close thermal. then demonstrate how reduce first by adiabatic cooling, and truncating Boltzmann atom. This provides nondeterministic way prepare atoms at low micro-K temperatures, ground state trapping potential.

We measure the coherent scattering of light by a cloud laser-cooled atoms with size comparable to wavelength light. By interfering laser beam tuned near an atomic resonance field scattered we observe red-shift, broadening, and saturation extinction for increasing atom numbers. attribute these features enhanced light-induced dipole-dipole interactions in cold, dense ensemble that result failure standard predictions such as "cooperative Lamb shift". The description mean-field model based on...

We describe the operation of a laser-cooled rubidium 87Rb frequency standard. present new measurement hyperfine with 1.3 × 10−14 relative accuracy, by comparison Cs fountain primary The measured ground-state splitting is ν87 = 6 834 682 610.90429(9) Hz. This value differs from previously published values (see Essen L., Hope E. G. and Sutcliffe D., Nature 189 1961 298; Penselin S., Moran T., Cohen W. Wscinkler G., Phys. Rev. 127 1962 524; Arditi M. Cerez P. IEEE Trans. Instrum. Meas. IM-21...

We present an optical system designed to capture and observe a single neutral atom in dipole trap, created by focusing laser beam using large-numerical-aperture $(\mathrm{NA}=0.5)$ aspheric lens. experimentally evaluate the performance of show that it is diffraction limited over broad spectral range $(\ensuremath{\sim}200\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ with large transverse field $(\ifmmode\pm\else\textpm\fi{}25\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m})$. The tweezer at...

We show that the resonance shifts in fluorescence of a cold gas rubidium atoms substantially differ from those thermal atomic ensembles obey standard continuous medium electrodynamics. The analysis is based on large-scale microscopic numerical simulations and experimental measurements steady-state response light propagation.

We demonstrate the lossless state-selective detection of a single rubidium 87 atom trapped in an optical tweezer. This is analogous to one used on ions. After preparation either dark or bright state, we probe internal state by sending laser light that couples excited only. The laser-induced fluorescence collected high numerical aperture lens. single-shot fidelity 98.6±0.2% and presently limited count noise detector. simplicity this method opens new perspectives view applications quantum...

We study the emergence of a collective optical response cold and dense $^{87}$Rb atomic cloud to near-resonant low-intensity light when atom number is gradually increased. Experimental observations are compared with microscopic stochastic simulations recurrent scattering processes between atoms that incorporate multilevel structure measurement setup. analyze an inhomogeneously-broadened gas find experimental resonance line shifts total collected scattered intensity in clouds substantially...

We measure the coherent scattering of low-intensity, near-resonant light by a cloud laser-cooled two-level rubidium atoms with size comparable to wavelength light. isolate atomic structure applying 300-G magnetic field. both temporal and steady-state optical response for various detunings laser atom numbers ranging from 5 100. compare our results microscopic coupled-dipole model multimode, paraxial Maxwell-Bloch model. In low-intensity regime, models are in excellent agreement, thus...

We measure the near-resonant transmission of light through a dense medium potassium vapor confined in cell with nanometer thickness order to investigate origin and validity collective Lamb shift. A complete model including multiple reflections nanocell reproduces accurately observed line shape. It allows extraction density-dependent shift width bulk atomic resonance, deconvolved from cavity effect. observe an additional, unexpected dependence medium. This extra demands further experimental...

We present measurements of cavity frequency pulling and collisional shifts in a 87Rb fountain with resolution 3x10(-16). Agreement theory is found for the measured shifts. The clock shift at least 50 times smaller than 133Cs.

We present a new method based on transfer of population by adiabatic passage that allows one to prepare cold atomic samples with well-defined ratio density and atom number. This is used perform measurement the collision frequency shift in laser cooled cesium clock at percent level, which makes evaluation fountain accuracy 10(-16) level realistic. With improvements, would allow measurements density-dependent phase shifts 10(-3) high precision experiments.

We analyze resonant light scattering by an atomic cloud in a regime where near-field interactions between scatterers cannot be neglected. first use microscopic approach and calculate numerically the eigenmodes of for many different realizations. It is found that there always exists small number polaritonic modes are spatially coherent superradiant. show dominated these modes. then macroscopic introducing effective permittivity so equivalent to dielectric particle. one-to-one correspondence...

We study light-assisted collisions in an ensemble containing a small number ($\ensuremath{\sim}$3) of cold ${}^{87}$Rb atoms trapped microscopic dipole trap. Using our ability to operate with one atom exactly the trap, we measure one-body heating rate associated near-resonant laser excitation, and use this measurement extract two-body loss when few are present Our measurements indicate that can reach surprisingly large values $\ensuremath{\beta}>{10}^{\ensuremath{-}8}$ cm${}^{3}$...

We demonstrate experimentally that a cloud of cold atoms with size comparable to the wavelength light can induce large group delays on laser pulse when is tightly focused it and close an atomic resonance. Delays as -10 ns are observed, corresponding "superluminal" propagation negative velocities low -300 m/s. Strikingly, this delay associated moderate extinction owing very small light-induced interactions between atoms. It implies phase shift imprinted continuous beam, opens interesting...

By measuring the transmission of near-resonant light through an atomic vapor confined in a nano-cell we demonstrate mesoscopic optical response arising from non-locality induced by motion atoms with phase coherence length larger than cell thickness. Whereas conventional dispersion theory -- where local is simply convolved Maxwell-Boltzmann velocity distribution unable to reproduce measured spectra, model including non-local, size-dependent susceptibility found be excellent agreement...

This paper reviews recent progress on microwave clocks using laser cooled neutral atoms. With an ultra-stable cryogenic sapphire oscillator as interrogation oscillator, a cesium fountain operates at the quantum projection noise limit. 6 · 105 detected atoms, relative frequency stability δv/v is 4 10-14τ-1/2 where τ integration time in seconds. comparable to that of hydrogen masers. At = 2 104 s, measured reaches 10-16. Equally important accuracy standard since 133Cs primary reference for...

We demonstrate experimentally the evaporative cooling of a few hundred rubidium-87 atoms in single-beam microscopic dipole trap. Starting with 800 at temperature 125 $\ensuremath{\mu}$K, we produce an unpolarized sample 40 110 nK, within 3 s. The phase-space density end evaporation reaches unity, close to quantum degeneracy. gain after is ${10}^{3}$. find that scaling laws used for much larger numbers are still valid despite small number involved process. also compare our results simple...

We report the efficient and fast ($\sim 2\mathrm{Hz}$) preparation of randomly loaded 1D chains individual $^{87}$Rb atoms dense atomic clouds trapped in optical tweezers using a new experimental platform. This platform is designed for study both structured disordered systems free space. It composed two high-resolution perpendicular to each other, enhancing observation manipulation capabilities. The setup includes dynamically controllable telescope, which we use vary tweezer beam waist. A D1...