Gyroscopes based on nitrogen-vacancy centers in diamond

We propose solid-state gyroscopes based on ensembles of negatively charged nitrogen-vacancy (${\rm NV^-}$) centers in diamond. In one scheme, rotation of the nitrogen-vacancy symmetry axis will induce Berry phase shifts in the ${\rm NV^{-}}$ electronic ground-state coherences proportional to the solid angle subtended by the symmetry axis. We estimate sensitivity in the range of $5\times10^{-3} {\rm rad/s/\sqrt{Hz}}$ in a 1 ${\rm mm^3}$ sensor volume using a simple Ramsey sequence. Incorporating dynamical decoupling to suppress dipolar relaxation may yield sensitivity at the level of $10^{-5} {\rm rad/s/\sqrt{Hz}}$. With a modified Ramsey scheme, Berry phase shifts in the ${\rm ^{14}N}$ hyperfine sublevels would be employed. The projected sensitivity is in the range of $10^{-5} {\rm rad/s/\sqrt{Hz}}$, however the smaller gyromagnetic ratio reduces sensitivity to magnetic-field noise by several orders of magnitude. Reaching $10^{-5} {\rm rad/s/\sqrt{Hz}}$ would represent an order of magnitude improvement over other compact, solid-state gyroscope technologies.Comment: 3 figures, 5 page

Nonlinear magneto-optical rotation of frequency-modulated light resonant with a low-J transition

A low-light-power theory of nonlinear magneto-optical rotation of frequency-modulated light resonant with a J=1->J'=0 transition is presented. The theory is developed for a Doppler-free transition, and then modified to account for Doppler broadening and velocity mixing due to collisions. The results of the theory are shown to be in qualitative agreement with experimental data obtained for the rubidium D1 line.Comment: 11 pages, 5 figures, v.2 edited for clarit

How do you know if you ran through a wall?

Stable topological defects of light (pseudo)scalar fields can contribute to the Universe's dark energy and dark matter. Currently the combination of gravitational and cosmological constraints provides the best limits on such a possibility. We take an example of domain walls generated by an axion-like field with a coupling to the spins of standard-model particles, and show that if the galactic environment contains a network of such walls, terrestrial experiments aimed at detection of wall-crossing events are realistic. In particular, a geographically separated but time-synchronized network of sensitive atomic magnetometers can detect a wall crossing and probe a range of model parameters currently unconstrained by astrophysical observations and gravitational experiments.Comment: 5 pages, 2 figure; to appear in the PR

Hyperfine-interaction- and magnetic-field-induced Bose-Einstein-statistics suppressed two-photon transitions

Two-photon transitions between atomic states of total electronic angular momentum $J_a=0$ and $J_b=1$ are forbidden when the photons are of the same energy. This selection rule is analogous to the Landau-Yang theorem in particle physics that forbids decays of vector particle into two photons. It arises because it is impossible to construct a total angular momentum $J_{2\gamma}=1$ quantum-mechanical state of two photons that is permutation symmetric, as required by Bose-Einstein statistics. In atoms with non-zero nuclear spin, the selection rule can be violated due to hyperfine interactions. Two distinct mechanisms responsible for the hyperfine-induced two-photon transitions are identified, and the hyperfine structure of the induced transitions is evaluated. The selection rule is also relaxed, even for zero-nuclear-spin atoms, by application of an external magnetic field. Once again, there are two similar mechanisms at play: Zeeman splitting of the intermediate-state sublevels, and off-diagonal mixing of states with different total electronic angular momentum in the final state. The present theoretical treatment is relevant to the ongoing experimental search for a possible Bose-Einstein-statistics violation using two-photon transitions in barium, where the hyperfine-induced transitions have been recently observed, and the magnetic-field-induced transitions are being considered both as a possible systematic effect, and as a way to calibrate the measurement

Quantum computing with magnetic atoms in optical lattices of reduced periodicity

We investigate the feasibility of combining Raman optical lattices with a quantum computing architecture based on lattice-confined magnetically interacting neutral atoms. A particular advantage of the standing Raman field lattices comes from reduced interatomic separations leading to increased interatomic interactions and improved multi-qubit gate performance. Specifically, we analyze a $J=3/2$ Zeeman system placed in $_{+}-\sigma_{-}$ Raman fields which exhibit $\lambda /4$ periodicity. We find that the resulting CNOT gate operations times are in the order of millisecond. We also investigate motional and magnetic-field induced decoherences specific to the proposed architecture

Magneto-optical rotation of spectrally impure fields and its nonlinear dependence on optical density

We calculate magneto-optical rptation of spectrally impure fileds in an optically thick cold atmic medium. We show that the spectral impurity leads to non-linear dependence of the rotation angle on optical density. Using our calculations, we provide a quanttative analysis of the recent experimental results of G. Labeyrie et al. [Phys. Rev. A 64, 033402 (2001)] using cold Rb$^{85}$ atoms.Comment: 6 pages, 5 Figures, ReVTeX4, Submitted to PR

Coherent population oscillations with nitrogen-vacancy color centers in diamond

We present results of our research on two-field (two-frequency) microwave spectroscopy in nitrogen-vacancy (NV-) color centers in a diamond. Both fields are tuned to transitions between the spin sublevels of the NV- ensemble in the 3A2 ground state (one field has a fixed frequency while the second one is scanned). Particular attention is focused on the case where two microwaves fields drive the same transition between two NV- ground state sublevels (ms=0 -> ms=+1). In this case, the observed spectra exhibit a complex narrow structure composed of three Lorentzian resonances positioned at the pump-field frequency. The resonance widths and amplitudes depend on the lifetimes of the levels involved in the transition. We attribute the spectra to coherent population oscillations induced by the two nearly degenerate microwave fields, which we have also observed in real time. The observations agree well with a theoretical model and can be useful for investigation of the NV relaxation mechanisms.Comment: 17 page

Detection of a single cobalt microparticle with a microfabricated atomic magnetometer

We present magnetic detection of a single, 2 {\mu}m diameter cobalt microparticle using an atomic magnetometer based on a microfabricated vapor cell. These results represent an improvement by a factor of 105 in terms of the detected magnetic moment over previous work using atomic magnetometers to detect magnetic microparticles. The improved sensitivity is due largely to the use of small vapor cells. In an optimized setup, we predict detection limits of 0.17 {\mu}m^3.Comment: 3 pages, 3 figure