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D. Budker

Publications and source records attributed to D. Budker.

At least 73 records · Page 4Linked to original sources
arXiv2014

All-Optical Vector Atomic Magnetometer

We demonstrate an all-optical magnetometer capable of measuring the magnitude and direction of a magnetic field using nonlinear magneto-optical rotation in a cesium vapor. Vector capability is added by effective modulation of the field along orthogonal axes and subsequent demodulation of the magnetic-resonance frequency. This modulation is provided by the AC Stark shift induced by circularly polarized laser beams. The sensor exhibits a demonstrated rms noise floor of 50 fT/Hz^(1/2) in measurement of the field magnitude and 0.5 mrad/Hz^(1/2) in the field direction; elimination of technical noise would improve these sensitivities to 12 fT/Hz^(1/2) and 5 microrad/Hz^(1/2), respectively. Applications for a precise all-optical vector magnetometer would include magnetically sensitive fundamental physics experiments, such as the search for a permanent electric dipole moment of the neutron.

physics.atom-ph↗
arXiv2014

Stark shift and parity non-conservation for near-degenerate states of xenon

We identify a pair of near-degenerate states of opposite parity in atomic Xe, the $5p^5 10s \,\, ^2[3/2]_2^o$ at $\rm{E}=94759.927$ cm$^{-1}$ and $5p^5 6f \,\, ^2[5/2]_2$ at $\rm{E}= 94759.935$ cm$^{-1}$, for which parity- and time-odd effects are expected to be enhanced by the small energy separation. We present theoretical calculations which indicate narrow widths for both states and we report a calculated value for the weak matrix element, arising from configuration mixing, of $|W|=2.1$ Hz for $^{132}$Xe. In addition, we measured the Stark effect of the $5p^5\,6f$ $^2[5/2]_{2}$ and $5p^5 \,6f \ ^2[3/2]_2$ ($\rm{E} =94737.121\,\rm{cm}^{-1}$) states. The Stark-shift of the $6f$ states is observed to be negative, revealing the presence of nearby $6g$ states at higher energies, which have not been observed before. The Stark-shift measurements imply an upper limit on the weak matrix element of $|W|\!<\!5$ Hz for the near-degenerate states ($10s \,\, ^2[3/2]_2^o$ and $6f \,\, ^2[5/2]_2$), which is in agreement with the presented calculations.

physics.atom-ph↗
arXiv2014

Microwave saturation spectroscopy of nitrogen-vacancy ensembles in diamond

Negatively-charged nitrogen-vacancy (NV$^-$) centers in diamond have generated much recent interest for their use in sensing. The sensitivity improves when the NV ground-state microwave transitions are narrow, but these transitions suffer from inhomogeneous broadening, especially in high-density NV ensembles. To better understand and remove the sources of broadening, we demonstrate room-temperature spectral "hole burning" of the NV ground-state transitions. We find that hole burning removes the broadening caused by magnetic fields from $^{13}$C nuclei and demonstrate that it can be used for magnetic-field-insensitive thermometry.

physics.optics↗
arXiv2014

Diamond Magnetometry of Superconducting Thin Films

In recent years diamond magnetometers based on the nitrogen-vacancy (NV) center have been of considerable interest for magnetometry applications at the nanoscale. An interesting application which is well suited for NV centers is the study of nanoscale magnetic phenomena in superconducting materials. We employ the magnetic sensitivity of NV centers in diamond to interrogate the magnetic properties of a thin-layer yttrium barium copper oxide (YBCO) superconductor. Using fluorescence-microscopy methods and samples integrated with an NV sensor on a microchip, we measure the temperature of phase transition in the layer to be 70.0(2) K, and the penetration field of vortices to be 46(4) G. We observe the pinning of the vortices in the layer at 65 K, and estimate their density after cooling the sample in a ~ 10 G field to be 0.45(1) μm^{-2}. These measurements are done with a 10 nm thick NV layer, so that high spatial resolution may be enabled in the future. Based on these results, we anticipate that this magnetometer could be useful for imaging the structure and dynamics of vortices. As an outlook, we present a fabrication method for a superconductor chip designed for this purpose.

cond-mat.supr-con↗
arXiv2014

Cavity-enhanced room-temperature magnetometry using absorption by nitrogen-vacancy centers in diamond

We demonstrate a cavity-enhanced room-temperature magnetic field sensor based on nitrogen-vacancy centers in diamond. Magnetic resonance is detected using absorption of light resonant with the 1042 nm spin-singlet transition. The diamond is placed in an external optical cavity to enhance the absorption, and significant absorption is observed even at room temperature. We demonstrate a magnetic field sensitivity of 2.5 nT/sqrt(Hz), and project a photon shot-noise-limited sensitivity of 70 pT/sqrt(Hz) for a few mW of infrared light, and a quantum projection-noise-limited sensitivity of 250 fT/sqrt(Hz) for the sensing volume of 90 um x 90 um 200 um.

quant-ph↗
arXiv2013

Investigation of ac-Stark shifts in excited states of dysprosium relevant to testing fundamental symmetries

We report on measurements of the differential polarizability between the nearly degenerate, opposite parity states in atomic dysprosium at 19797.96 cm$^{-1}$. The differential scalar and tensor polarizabilities due to additional states were measured for the $|M| = 7,...,10$ sublevels in $^{164}$Dy and $^{162}$Dy and determined to be $\bar{\boldsymbolα}_{\scriptscriptstyle BA}^{(0)} = 180\,(45)_\text{stat}\,(8)_\text{sys}$ $\text{mHz}/(\mathrm{V}/\mathrm{cm})^2$ and $\bar{\boldsymbolα}_{\scriptscriptstyle BA}^{(2)} = -163\,(65)_\text{stat}\,(5)_\text{sys}$ $\text{mHz}/(\mathrm{V}/\mathrm{cm})^2$, respectively. The average blackbody radiation induced Stark shift of the Zeeman spectrum was measured around 300 K and found to be $-34(4)$ mHz/K and $+29(4)$ mHz/K for $^{164}$Dy and $^{162}$Dy, respectively. We conclude that ac-Stark related systematics will not limit a search for variation of the fine-structure constant, using dysprosium, down to the level of $|\dotα/α|=2.6\times10^{-17}$ yr$^{-1}$, for two measurements of the transition frequency one year apart.

physics.atom-ph↗
arXiv2013

The Infrared Absorption Band and Vibronic Structure of the Nitrogen-Vacancy Center in Diamond

Negatively-charged nitrogen-vacancy (NV$^-$) color centers in diamond have generated much interest for use in quantum technology. Despite the progress made in developing their applications, many questions about the basic properties of NV$^-$ centers remain unresolved. Understanding these properties can validate theoretical models of NV$^-$, improve their use in applications, and support their development into competitive quantum devices. In particular, knowledge of the phonon modes of the $^1A_1$ electronic state is key for understanding the optical pumping process. Using pump-probe spectroscopy, we measured the phonon sideband of the ${^1}E\rightarrow{^1}A_1$ electronic transition in the NV$^-$ center. From this we calculated the ${^1}E\rightarrow{^1}A_1$ one-phonon absorption spectrum and found it to differ from that of the ${^3}E\rightarrow{^3}A_2$ transition, a result which is not anticipated by previous group-theoretical models of the NV$^-$ electronic states. We identified a high-energy 169 meV localized phonon mode of the $^1A_1$ level.

physics.atom-ph↗
arXiv2013

Limits on Violations of Lorentz Symmetry and the Einstein Equivalence Principle using Radio-Frequency Spectroscopy of Atomic Dysprosium

We report a joint test of local Lorentz invariance and the Einstein equivalence principle for electrons, using long-term measurements of the transition frequency between two nearly degenerate states of atomic dysprosium. We present many-body calculations which demonstrate that the energy splitting of these states is particularly sensitive to violations of both special and general relativity. We limit Lorentz violation for electrons at the level of $10^{-17}$, matching or improving the best laboratory and astrophysical limits by up to a factor of 10, and improve bounds on gravitational redshift anomalies for electrons by 2 orders of magnitude, to $10^{-8}$. With some enhancements, our experiment may be sensitive to Lorentz violation at the level of $9\times 10^{-20}$.

hep-ph↗
arXiv2013

Global Network of Optical Magnetometers for Exotic (GNOME): Physics Novel scheme for exotic physics searches

A novel experimental scheme enabling investigation of transient exotic spin couplings is discussed. The scheme is based on synchronous measurements of optical-magnetometer signals of several devices operating in magnetically shielded environments in distant locations ($\gtrsim100$ km). Although signatures of such exotic couplings may be present in the signal from a single magnetometer, it would be challenging to distinguish them from noise. By analyzing the correlation between signals from multiple, geographically separated magnetometers, it is not only possible to identify the exotic transient but also to investigate its nature. The ability of the network to probe presently unconstrained physics beyond the Standard Model is examined by considering the spin coupling to stable topological defects (e.g., domain walls) of axion-like fields. In the spirit of this research, a brief ($\sim 2$ hours) demonstration experiment involving two magnetometers located in Kraków and Berkeley ($\sim 9000$ km separation) is presented and discussion of the data-analysis approaches that may allow for the transient signal identification is provided. The prospects of the network are outlined in the last part of the paper.

physics.atom-ph↗
arXiv2013

New limits on variation of the fine-structure constant using atomic dysprosium

We report on the spectroscopy of radio-frequency transitions between nearly-degenerate, opposite-parity excited states in atomic dysprosium (Dy). Theoretical calculations predict that these states are very sensitive to variation of the fine-structure constant, $α$, owing to large relativistic corrections of opposite sign for the opposite-parity levels. The near degeneracy reduces the relative precision necessary to place constraints on variation of $α$ competitive with results obtained from the best atomic clocks in the world. Additionally, the existence of several abundant isotopes of Dy allows isotopic comparisons that suppress common-mode systematic errors. The frequencies of the 754-MHz transition in $^{164}$Dy and 235-MHz transition in $^{162}$Dy were measured over the span of two years. Linear variation of $α$ is found to be $\dotα/α= (-5.8\pm6.9)\times10^{-17}$ yr$^{-1}$, consistent with zero. The same data are used to constrain the dimensionless parameter $k_α$, characterizing a possible coupling of $α$ to a changing gravitational potential. We find that $k_α= (-5.5\pm5.2)\times10^{-7}$, essentially consistent with zero and the best constraint to date.

physics.atom-ph↗
arXiv2012

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.

hep-ph↗
arXiv2012

Light narrowing of magnetic resonances in ensembles of nitrogen-vacancy centers in diamond

We investigate optically detected magnetic resonance signals from an ensemble of nitrogen-vacancy centers in diamond. The signals are measured for different light powers and microwave powers, and the contrast and linewidth of the magnetic-resonance signals are extracted. For a wide range of experimental settings of the microwave and light powers, the linewidth decreases with increasing light power, and more than a factor of two "light narrowing" is observed.Furthermore, we identify that spin-spin interaction between nitrogen-vacancy centers and substitutional nitrogen atoms in the diamond leads to changes in the lineshape and the linewidth of the optically detected magnetic-resonance signals. Finally, the importance of the light-narrowing effect for optimizing the sensitivity of magnetic field measurements is discussed.

quant-ph↗
arXiv2012

Small-sized Dichroic Atomic Vapor Laser Lock (DAVLL)

Two, lightweight diode laser frequency stabilization systems designed for experiments in the field are described. A significant reduction in size and weight in both models supports the further miniaturization of measurement devices in the field. Similar to a previous design, magnetic-field lines are contained within a magnetic shield enclosing permanent magnets and a Rb cell, so that these DAVLL systems may be used for magnetically sensitive instruments. The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a micro-fabricated cell (3 mm square), and requires heaters. These new systems show no degradation in performance with regard to previous designs, while considerably reducing dimensions.

physics.atom-ph↗
arXiv2012

Modeling of pulsed laser guide stars for the Thirty Meter Telescope project

The Thirty Meter Telescope (TMT) has been designed to include an adaptive optics system and associated laser guide star (LGS) facility to correct for the image distortion due to Earth's atmospheric turbulence and achieve diffraction-limited imaging. We have calculated the response of mesospheric sodium atoms to a pulsed laser that has been proposed for use in the LGS facility, including modeling of the atomic physics, the light-atom interactions, and the effect of the geomagnetic field and atomic collisions. This particular pulsed laser format is shown to provide comparable photon return to a continuous-wave (cw) laser of the same average power; both the cw and pulsed lasers have the potential to satisfy the TMT design requirements for photon return flux.

physics.atom-ph↗
arXiv2012

Temperature and magnetic field dependent longitudinal spin relaxation in nitrogen-vacancy ensembles in diamond

We present an experimental study of the longitudinal electron-spin relaxation time (T1) of negatively charged nitrogen-vacancy (NV) ensembles in diamond. T1 was studied as a function of temperature from 5 to 475 K and magnetic field from 0 to 630 G for several samples with various NV and nitrogen concentrations. Our studies reveal three processes responsible for T1 relaxation. Above room temperature, a two-phonon Raman process dominates, and below, we observe an Orbach-type process with an activation energy, 73(4) meV, which closely matches the local vibrational modes of the NV center. At yet lower temperatures, sample dependent cross relaxation processes dominate, resulting in temperature independent values of T1, from ms to minutes. The value of T1 in this limit depends sensitively on magnetic field and can be tuned by more than an order of magnitude.

cond-mat.mtrl-sci↗
arXiv2012

Polarized nuclear target based on parahydrogen induced polarization

We discuss a novel concept of a polarized nuclear target for accelerator fixed-target scattering experiments, which is based on parahydrogen induced polarization (PHIP). One may be able to reach a 33% free-proton polarization in the ethane molecule. The potential advantages of such a target include operation at zero magnetic field, fast ($\sim$100 Hz) polarization reversal, and operation with large intensity of an electron beam.

nucl-ex↗
arXiv2012

Orientation-to-alignment conversion and spin squeezing

The relationship between orientation-to-alignment conversion (a form of atomic polarization evolution induced by an electric field) and the phenomenon of spin squeezing is demonstrated. A "stretched" state of an atom or molecule with maximum angular-momentum projection along the quantization axis possesses orientation and is a quantum-mechanical minimum-uncertainty state, where the product of the equal uncertainties of the angular-momentum projections on two orthogonal directions transverse to the quantization axis is the minimum allowed by the uncertainty relation. Application of an electric field for a short time induces orientation-to-alignment conversion and produces a spin-squeezed state, in which the quantum state essentially remains a minimum-uncertainty state, but the uncertainties of the angular-momentum projections on the orthogonal directions are unequal. This property can be visualized using the angular-momentum probability surfaces, where the radius of the surface is given by the probability of measuring the maximum angular-momentum projection in that direction. Brief remarks are also given concerning collective-spin squeezing and quantum nondemolition measurements.

physics.atom-ph↗