Larkin-Ovchinnikov-Fulde-Ferrell phase in the superconductor (TMTSF)2ClO4: Theory versus experiment

We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its conducting chains, where we take into account both the paramagnetic spin-splitting and orbital destructive effects against superconductivity. We show that, due to a relative weakness of the orbital effects in a Q1D case, the LOFF phase appears in (TMTSF)$_2$ClO$_4$ superconductor for real values of its Q1D band parameters. We compare our theoretical calculations with the recent experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett. \textbf{100}, 117002 (2008)] and show that there is a good qualitative and quantitative agreement between the theory and experimental data.Comment: 4 pages, 1 figur

Precise measurement of hyperfine structure in the 2P1/2{2P}_{1/2} state of 7^{7}Li using saturated-absorption spectroscopy

We report a precise measurement of the hyperfine interval in the ${2P}_{1/2}$ state of $^{7}$Li. The transition from the ground state ($D_1$ line) is accessed using a diode laser and the technique of saturated-absorption spectroscopy in hot Li vapor. The interval is measured by locking an acousto-optic modulator to the frequency difference between the two hyperfine peaks. The measured interval of 92.040(6)~MHz is consistent with an earlier measurement reported by us using an atomic-beam spectrometer [Das and Natarajan, J.\ Phys.\ B {\bf 41}, 035001 (2008)]. The interval yields the magnetic dipole constant in the $P_{1/2}$ state as $A=46.047(3)$, which is discrepant from theoretical calculations by $>80$~kHz.Comment: 5 pages, 3 figure

Spectroscopy of atomic rubidium at 500 bar buffer gas pressure: approaching the thermal equilibrium of dressed atom-light states

We have recorded fluorescence spectra of the atomic rubidium D-lines in the presence of several hundreds of bars buffer gas pressure. With additional saturation broadening a spectral linewidth comparable to the thermal energy of the atoms in the heated gas cell is achieved. An intensity-dependent blue asymmetry of the spectra is observed, which becomes increasingly pronounced when extrapolating to infinitely high light intensity. We interpret our results as evidence for the dressed (coupled atom-light) states to approach thermal equilibrium.Comment: 4 page

Coherent, multi-heterodyne spectroscopy using stabilized optical frequency combs

The broadband, coherent nature of narrow-linewidth fiber frequency combs is exploited to measure the full complex spectrum of a molecular gas through multi-heterodyne spectroscopy. We measure the absorption and phase shift experienced by each of 155,000 individual frequency comb lines, spaced by 100 MHz and spanning from 1495 nm to 1620 nm, after passing through a hydrogen cyanide gas. The measured phase spectrum agrees with Kramers-Kronig transformation of the absorption spectrum. This technique can provide a full complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.Comment: 4 pages, 3 figure

Coherence assisted resonance with sub-lifetime-limited linewidth

We demonstrate a novel approach to obtain resonance linewidth below that limited by coherence lifetime. Cross correlation between induced intensity modulation of two lasers coupling the target resonance exhibits a narrow spectrum. 1/30 of the lifetime-limited width was achieved in a proof-of-principle experiment where two ground states are the target resonance levels. Attainable linewidth is only limited by laser shot noise in principle. Experimental results agree with an intuitive analytical model and numerical calculations qualitatively. This technique can be easily implemented and should be applicable to many atomic, molecular and solid state spin systems for spectroscopy, metrology and resonance based sensing and imaging.Comment: 5 pages 5 figure

Thermalization via Heat Radiation of an Individual Object Thinner than the Thermal Wavelength

Modeling and investigating the thermalization of microscopic objects with arbitrary shape from first principles is of fundamental interest and may lead to technical applications. Here, we study, over a large temperature range, the thermalization dynamics due to far-field heat radiation of an individual, deterministically produced silica fiber with a predetermined shape and a diameter smaller than the thermal wavelength. The temperature change of the subwavelength-diameter fiber is determined through a measurement of its optical path length in conjunction with an ab initio thermodynamic model of the fiber structure. Our results show excellent agreement with a theoretical model that considers heat radiation as a volumetric effect and takes the emitter shape and size relative to the emission wavelength into account

Power Dependent Lineshape Corrections for Quantitative Spectroscopy

The Voigt profile - a convolution of a Gaussian and a Lorentzian - accurately describes the absorption lines of atomic and molecular gases at low probe powers. Fitting such to experimental spectra yields both the Lorentzian natural linewidth and the Gaussian Doppler broadening. However, as the probe power increases saturation effects introduce spurious power dependence into the fitted Doppler width. Using a simple atomic model, we calculate power-dependent corrections to the Voigt profile, which are parametrized by the Gaussian Doppler width, the Lorentzian natural linewidth, and the optical depth. We show numerically and experimentally that including the correction term substantially reduces the spurious power dependence in the fitted Gaussian width.Comment: 4 pages, 3 figure

Quantum Computation with Diatomic Bits in Optical Lattices

We propose a scheme for scalable and universal quantum computation using diatomic bits with conditional dipole-dipole interaction, trapped within an optical lattice. The qubit states are encoded by the scattering state and the bound heteronuclear molecular state of two ultracold atoms per site. The conditional dipole-dipole interaction appears between neighboring bits when they both occupy the molecular state. The realization of a universal set of quantum logic gates, which is composed of single-bit operations and a two-bit controlled-NOT gate, is presented. The readout method is also discussed.Comment: 5 pages, 1 eps figure, accepted for publication in Phys. Rev.

Nonlinear magneto-optical rotation in optically thick media

Nonlinear magneto-optical rotation is a sensitive technique for measuring magnetic fields. Here, the shot-noise-limited magnetometric sensitivity is analyzed for the case of optically-thick media and high light power, which has been the subject of recent experimental and theoretical investigations.Comment: 7 pages, 4 figure

Slow light in paraffin-coated Rb vapor cells

We present preliminary results from an experimental study of slow light in anti-relaxation-coated Rb vapor cells, and describe the construction and testing of such cells. The slow ground state decoherence rate allowed by coated cell walls leads to a dual-structured electromagnetically induced transparency (EIT) spectrum with a very narrow (<100 Hz) transparency peak on top of a broad pedestal. Such dual-structure EIT permits optical probe pulses to propagate with greatly reduced group velocity on two time scales. We discuss ongoing efforts to optimize the pulse delay in such coated cell systems.Comment: 6 pages, 6 figures, submitted to Journal of Modern Optic