Two-photon spectroscopy of the 6S_(1/2) → 6D_(5/2) transition of trapped atomic cesium

Two-photon spectroscopy of atomic cesium confined and cooled in a magneto-optical trap is reported. The hyperfine structure of the 6D_(5/2) state is determined with 1% accuracy. New capabilities for studying ac Stark shifts and kinetic transport for cold atoms are suggested

Frequency metrology by use of quantum interference

Quantum interference in the rate of two-photon excitation of the 6S1/2 → 6P3/2 → 6D5/2 transition in atomic cesium is exploited to demonstrate phase-sensitive frequency demodulation for an optical interval of 612.5 THz. By thus using atoms as ultrafast nonlinear mixing elements, we suggest and analyze a new avenue for absolute comparisons of a dense set of frequencies over the range of 200–2000 nm

Atoms as nonlinear mixers for detection of quantum correlations at ultrahigh frequencies

Measurements of quantum correlations are reported for a frequency difference of 25 THz between the signal and idler output fields generated by a subthreshold nondegenerate optical parametric oscillator. By simultaneously exciting a two-photon transition in atomic Cs by a combination of signal, idler, and "references oscillator" fields, we record modulation of the excited-state population due to quantum interference between two alternative excitation pathways. The observed phase-sensitive modulation is proportional to the correlation function〈EsEi〉for the quantized signal and idler fields

Quantum interference in two-photon excitation with squeezed and coherent fields

Two-photon excitation of a three-level atom in a ladder configuration (1-->2-->3) by simultaneous illumination with fields in squeezed vacuum and coherent states results in quantum interference for the excitation process. The particular configuration considered here is one for which the signal and idler output fields of a subthreshold nondegenerate optical parametric oscillator are in resonance with the two-stepwise dipole atomic transitions (1-->2,2-->3), while a "reference oscillator" field is in two-photon resonance with the quadrupole transition (1-->3). In an extension of the work of Ficek and Drummond [Phys. Rev. A 43, 6247 (1991)], a theoretical formulation based on the full quantum master equation for the problem is presented. The combined effects of quantum interference and the nonclassical character of the squeezed state are investigated, and offer the potential for a new detection strategy for quantum fluctuations of the electromagnetic field with ultrahigh frequencies (10's-100's THz). Based on the theory developed, we analyze quantum interference in excitation in several special cases relevant to experimental realizations, including the effects of a small focusing angle of the squeezing onto the atoms, and unusual population inversions. Special emphasis is given to identifying intrinsically quantum optical field effects versus classical field effects. Procedures that could distinguish between the two (i.e., classical and nonclassical) are suggested

SURVEYING FOR RANAVIRUS IN GREEN FROGS (LITHOBATES CLAMITANS) AT FIVE LOCATIONS IN INDIANA

Ranaviruses are an emerging pathogen within the United States that infects amphibians, reptiles, and fish. A Frog Virus 3-like (FV3) ranavirus has been detected at only two locations in Indiana; however, there have been few attempts to broadly sample for ranaviruses to determine their distribution across the state. This knowledge is necessary for the continued management and conservation of native amphibian populations. Our objective was to assess the occurrence of FV3-like ranaviruses in larval Green Frog (Lithobates clamitans) populations at five sites located in different regions of Indiana. Tissue samples were collected from 166 individuals and were assayed using both conventional and qPCR methods. We did not detect the presence of any FV3-like ranaviruses at any of the five sites with either PCR method, suggesting the possibility that at these sites, FV3-like ranaviruses may not be present. However, continued sampling should be carried out to monitor the status of the presence of ranaviruses in this portion of the Midwest

Compact Source of EPR Entanglement and Squeezing at Very Low Noise Frequencies

We report on the experimental demonstration of strong quadrature EPR entanglement and squeezing at very low noise sideband frequencies produced by a single type-II, self-phase-locked, frequency degenerate optical parametric oscillator below threshold. The generated two-mode squeezed vacuum state is preserved for noise frequencies as low as 50 kHz. Designing simple setups able to generate non-classical states of light in the kHz regime is a key challenge for high sensitivity detection of ultra-weak physical effects such as gravitational wave or small beam displacement

Cavity QED with high-Q whispering gallery modes

We report measurements of cavity-QED effects for the radiative coupling of atoms in a dilute vapor to the external evanescent field of a whispering-gallery mode (WGM) in a fused silica microsphere. The high Q (5 x 10^(7)), small mode volume (10^(-8) cm^(3)), and unusual symmetry of the microcavity evanescent field enable velocity-selective interactions between fields with photon number of order unity in the WGM and (N) over bar(T) similar to 1 atoms in the surrounding vapor

Generation of spatial antibunching with free propagating twin beams

We propose and implement a novel method to produce a spatial anti-bunched field with free propagating twin beams from spontaneous parametric down-conversion. The method consists in changing the spatial propagation by manipulating the transverse degrees of freedom through reflections of one of the twin beams. Our method use reflective elements eliminating losses from absorption by the objects inserted in the beams.Comment: Submitted for publication in Phys. Rev.

Demonstration of a state-insensitive, compensated nanofiber trap

We report the experimental realization of an optical trap that localizes single Cs atoms ≃ 215 nm from surface of a dielectric nanober. By operating at magic wavelengths for pairs of counterpropagating red- and blue-detuned trapping beams, dierential scalar light shifts are eliminated, and vector shifts are suppressed by ≈ 250. We thereby measure an absorption linewidth Γ/2π = 5.7 ± 0.1 MHz for the Cs 6S_(1/2), F = 4 → 6P_(3/2), F' = 5 transition, where Γ_0/2π = 5.2 MHz in free space. Optical depth d ≃ 66 is observed, corresponding to an optical depth per atom d_1 ≃ 0.08. These advances provide an important capability for the implementation of functional quantum optical networks and precision atomic spectroscopy near dielectric surfaces

Experimental observation of spatial antibunching of photons

We report an interference experiment that shows transverse spatial antibunching of photons. Using collinear parametric down-conversion in a Young-type fourth-order interference setup we show interference patterns that violate the classical Schwarz inequality and should not exist at all in a classical description.Comment: 4 pages, 7 figure