Stroboscopic back-action evasion in a dense alkali-metal vapor

We explore experimentally quantum non-demolition (QND) measurements of atomic spin in a hot potassium vapor in the presence of spin-exchange relaxation. We demonstrate a new technique for back-action evasion by stroboscopic modulation of the probe light. With this technique we study spin noise as a function of polarization for atoms with spin greater than 1/2 and obtain good agreement with a simple theoretical model. We point that in a system with fast spin-exchange, where the spin relaxation rate is changing with time, it is possible to improve the long-term sensitivity of atomic magnetometry by using QND measurements

High Bandwidth Atomic Magnetometery with Continuous Quantum Non-demolition Measurements

We describe an experimental study of spin-projection noise in a high sensitivity alkali-metal magnetometer. We demonstrate a four-fold improvement in the measurement bandwidth of the magnetometer using continuous quantum non-demolition (QND) measurements. Operating in the scalar mode with a measurement volume of 2 cm^3 we achieve magnetic field sensitivity of 22 fT/Hz^(1/2) and a bandwidth of 1.9 kHz with a spin polarization of only 1%. Our experimental arrangement is naturally back-action evading and can be used to realize sub-fT sensitivity with a highly polarized spin-squeezed atomic vapor.Comment: 4 page

Limits on new long range nuclear spin-dependent forces set with a K-3He co-magnetometer

A magnetometer using spin-polarized K and $^3$He atoms occupying the same volume is used to search for anomalous nuclear spin-dependent forces generated by a separate $^3$He spin source. We measure changes in the $^3$He spin precession frequency with a resolution of 18 pHz and constrain anomalous spin forces between neutrons to be less than $2 \times 10^{-8}$ of their magnetic or less than $2\times 10^{-3}$ of their gravitational interactions on a length scale of 50 cm. We present new limits on neutron coupling to light pseudoscalar and vector particles, including torsion, and constraints on recently proposed models involving unparticles and spontaneous breaking of Lorentz symmetry.Comment: 4 pages, 4 figures, latest version as appeared in PR

A Low-Noise High-Density Alkali Metal Scalar Magnetometer

We present an experimental and theoretical study of a scalar atomic magnetometer using an oscillating field-driven Zeeman resonance in a high-density optically-pumped potassium vapor. We describe an experimental implementation of an atomic gradiometer with a noise level below 10 fT/Hz^{1/2}, fractional field sensitivity below 10^{-9}/Hz^{1/2}, and an active measurement volume of about 1.5 cm^3. We show that the fundamental field sensitivity of a scalar magnetometer is determined by the rate of alkali-metal spin-exchange collisions even though the resonance linewidth can be made much smaller than the spin-exchange rate by pumping most atoms into a stretched spin state.Comment: 10 pages, 7 figures. Version 2 is longer, with more complete description of theoretical analysis and comparison between analytical and experimental result

The Family \u3cem\u3eRhabdoviridae\u3c/em\u3e: Mono- and Bipartite Negative-Sense RNA Viruses with Diverse Genome Organization and Common Evolutionary Origins

The family Rhabdoviridae consists of mostly enveloped, bullet-shaped or bacilliform viruses with a negative-sense, single-stranded RNA genome that infect vertebrates, invertebrates or plants. This ecological diversity is reflected by the diversity and complexity of their genomes. Five canonical structural protein genes are conserved in all rhabdoviruses, but may be overprinted, overlapped or interspersed with several novel and diverse accessory genes. This review gives an overview of the characteristics and diversity of rhabdoviruses, their taxonomic classification, replication mechanism, properties of classical rhabdoviruses such as rabies virus and rhabdoviruses with complex genomes, rhabdoviruses infecting aquatic species, and plant rhabdoviruses with both mono- and bipartite genomes

Decoherence-free radiofrequency dressed subspaces

We study the spectral signatures and coherence properties of radiofrequency dressed hyperfine Zeeman sub-levels of 87Rb. Experimentally, we engineer combinations of static and RF magnetic fields to modify the response of the atomic spin states to environmental magnetic field noise. We demonstrate analytically and experimentally the existence of 'magic' dressing conditions where decoherence due to electromagnetic field noise is strongly suppressed. Building upon this result, we propose a bi-chromatic dressing configuration that reduces the global sensitivity of the atomic ground states to low-frequency noise, and enables the simultaneous protection of multiple transitions between the two ground hyperfine manifolds of atomic alkali species. Our methods produce protected transitions between any pair of hyperfine sub-levels at arbitrary (low) DC-magnetic fields.Comment: 14 pages, 12 figure