Search

This Letter reports new results from the HAYSTAC experiment's search for dark matter axions in our galactic halo. It represents the widest search to date that utilizes squeezing to realize sub-quantum limited noise. The new results cover 1.71 $\mu$eV of newly scanned parameter space in the mass ranges 17.28--18.44 $\mu$eV and 18.71--19.46 $\mu$eV. No statistically significant evidence of an axion signal was observed, excluding couplings $|g_\gamma|\geq$ 2.75$\times$$|g_{\gamma}^{\text{KSVZ}}|$ and $|g_\gamma|\geq$ 2.96$\times$$|g_{\gamma}^{\text{KSVZ}}|$ at the 90$\%$ confidence level over the respective region. By combining this data with previously published results using HAYSTAC's squeezed state receiver, a total of 2.27 $\mu$eV of parameter space has now been scanned between 16.96--19.46 $\mu$eV, excluding $|g_\gamma|\geq$ 2.86$\times$$|g_{\gamma}^{\text{KSVZ}}|$ at the 90$\%$ confidence level. These results demonstrate the squeezed state receiver's ability to probe axion models over a significant mass range while achieving a scan rate enhancement relative to a quantum-limited experiment., Comment: 6 pages, 3 figures

The possible use of optically pumped $^{199}$Hg nuclear spin magnetometry for fundamental physics studies, particularly in the search for electric dipole moments, remains of great interest. Understanding surface-induced relaxation is necessary for the development of both large- and small-volume cells that have a long and stable nuclear spin lifetime. Such cells are critical to several ongoing experiments, including the measurement of the neutron electric dipole moment, zero or otherwise. $^{199}$Hg, due to its large mass, has a multitude of bound surface states that affect the interaction time with the surface and are an important factor in the interpretation of previously acquired data. It is shown that the inclusion of these states brings consistency to the derived surface interaction properties., Comment: 4 pages

A search for dark matter axions with masses $>10 \mu eV/c^{2}$ has been performed using the HAYSTAC experiment's squeezed state receiver to achieve sub-quantum limited noise. This report includes details of the design and operation of the experiment previously used to search for axions in the mass ranges $16.96-17.12$ and $17.14-17.28 \mu eV/c^{2}$($4.100-4.140$GHz) and $4.145-4.178$GHz) as well as upgrades to facilitate an extended search at higher masses. These upgrades include improvements to the data acquisition routine which have reduced the effective dead time by a factor of 5, allowing for the new region to be scanned $\sim$1.6 times faster with comparable sensitivity. No statistically significant evidence of an axion signal is found in the range $18.44-18.71\mu eV/c^{2}$($4.459-4.523$GHz), leading to an aggregate upper limit exclusion at the $90\%$ level on the axion-photon coupling of $2.06\times g_{\gamma}^{KSVZ}$., Comment: 20 pages, 16 figures

Microwave cavity haloscopes are among the most sensitive direct detection experiments searching for dark matter axions via their coupling to photons. When the power of the expected microwave signal due to axion-photon conversion is on the order of $10^{-24}$~W, having the ability to validate the detector response and analysis procedure by injecting realistic synthetic axion signals becomes helpful. Here we present a method based on frequency hopping spread spectrum for synthesizing axion signals in a microwave cavity haloscope experiment. It allows us to generate a narrow and asymmetric shape in frequency space that mimics an axion's spectral distribution, which is derived from a Maxwell-Boltzmann distribution. In addition, we show that the synthetic axion's power can be calibrated with reference to the system noise. Compared to the synthetic axion injection in HAYSTAC phase I, we demonstrated synthetic signal injection with a more realistic lineshape and calibrated power.

In dark matter axion searches, quantum uncertainty manifests as a fundamental noise source, limiting the measurement of the quadrature observables used for detection. We use vacuum squeezing to circumvent the quantum limit in a search for a new particle. By preparing a microwave-frequency electromagnetic field in a squeezed state and near-noiselessly reading out only the squeezed quadrature, we double the search rate for axions over a mass range favored by recent theoretical projections. We observe no signature of dark matter axions in the combined $16.96-17.12$ and $17.14-17.28\space\mu\text{eV}/c^2$ mass window for axion-photon couplings above $g_{\gamma} = 1.38\times g_{\gamma}^\text{KSVZ}$, reporting exclusion at the 90% level., Comment: 7 pages, 4 figures

In experiments searching for axionic dark matter, the use of the standard threshold-based data analysis discards valuable information. We present a Bayesian analysis framework that builds on an existing processing protocol to extract more information from the data of coherent axion detectors such as operating haloscopes. The analysis avoids logical subtleties that accompany the standard analysis framework and enables greater experimental flexibility on future data runs. Performing this analysis on the existing data from the HAYSTAC experiment, we find improved constraints on the axion-photon coupling $g_\gamma$ while also identifying the most promising regions of parameter space within the $23.15$--$24.0$ $\mu$eV mass range. A comparison with the standard threshold analysis suggests a $36\%$ improvement in scan rate from our analysis, demonstrating the utility of this framework for future axion haloscope analyses., Comment: 22 pages, 5 figures

A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. The superfluid $^4$He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of $2-3\times 10^{-28}$ e-cm, with anticipated systematic uncertainties below this level.

The UCNA experiment was designed to measure the neutron $\beta$-asymmetry parameter $A_0$ using polarized ultracold neutrons (UCN). UCN produced via downscattering in solid deuterium were polarized via transport through a 7 T magnetic field, and then directed to a 1 T solenoidal electron spectrometer, where the decay electrons were detected in electron detector packages located on the two ends of the spectrometer. A value for $A_0$ was then extracted from the asymmetry in the numbers of counts in the two detector packages. We summarize all of the results from the UCNA experiment, obtained during run periods in 2007, 2008--2009, 2010, and 2011--2013, which ultimately culminated in a 0.67\% precision result for $A_0$., Comment: 6 pages, 7 figures, to appear in proceedings of the International Workshop on Particle Physics at Neutron Sources 2018

Novel experimental techniques are required to make the next big leap in neutron electric dipole moment experimental sensitivity, both in terms of statistics and systematic error control. The nEDM experiment at the Spallation Neutron Source (nEDM@SNS) will implement the scheme of Golub & Lamoreaux [Phys. Rep., 237, 1 (1994)]. The unique properties of combining polarized ultracold neutrons, polarized $^3$He, and superfluid $^4$He will be exploited to provide a sensitivity to $\sim 10^{-28}\,e{\rm \,\cdot\, cm}$. Our cryogenic apparatus will deploy two small ($3\,{\rm L}$) measurement cells with a high density of ultracold neutrons produced and spin analyzed in situ. The electric field strength, precession time, magnetic shielding, and detected UCN number will all be enhanced compared to previous room temperature Ramsey measurements. Our $^3$He co-magnetometer offers unique control of systematic effects, in particular the Bloch-Siegert induced false EDM. Furthermore, there will be two distinct measurement modes: free precession and dressed spin. This will provide an important self-check of our results. Following five years of "critical component demonstration," our collaboration transitioned to a "large scale integration" phase in 2018. An overview of our measurement techniques, experimental design, and brief updates are described in these proceedings., Comment: Submitted to proceedings of PPNS 2018 - International Workshop on Particle physics at Neutron Sources (https://www.webofconferences.org/epj-web-of-conferences-forthcoming-conferences/1148-ppns-2018)

We report on the results from a search for dark matter axions with the HAYSTAC experiment using a microwave cavity detector at frequencies between 5.6-5.8$\, \rm Ghz$. We exclude axion models with two photon coupling $g_{a\gamma\gamma}\,\gtrsim\,2\times10^{-14}\,\rm GeV^{-1}$, a factor of 2.7 above the benchmark KSVZ model over the mass range 23.15$\,<\,$$m_a \,$<$\,$24.0$\,\mu\rm eV$. This doubles the range reported in our previous paper. We achieve a near-quantum-limited sensitivity by operating at a temperature $T

The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was $184(32)$ UCN/cm$^3$, a four-fold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be $39(7)$ UCN/cm$^3$, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of $\sigma(d_n) = 3\times 10^{-27}$ $e\cdot$cm., Comment: 6 pages, 6 figures

We describe in detail the analysis procedure used to derive the first limits from the Haloscope at Yale Sensitive to Axion CDM (HAYSTAC), a microwave cavity search for cold dark matter (CDM) axions with masses above $20\ \mu\text{eV}$. We have introduced several significant innovations to the axion search analysis pioneered by the Axion Dark Matter eXperiment (ADMX), including optimal filtering of the individual power spectra that constitute the axion search dataset and a consistent maximum likelihood procedure for combining and rebinning these spectra. These innovations enable us to obtain the axion-photon coupling $|g_\gamma|$ excluded at any desired confidence level directly from the statistics of the combined data., Comment: 33 pages, 10 figures; added changes made in review process

We report here several technical improvements to the HAYSTAC (Haloscope at Yale Sensitive To Axion Cold dark matter) that have improved operational efficiency, sensitivity, and stability., Comment: 5 pages, submitted to the 2nd Workshop on Microwave Cavities and Detectors for Axion Research; added discussion of noise problem in ver. 2

We describe a dark matter axion detector designed, constructed, and operated both as an innovation platform for new cavity and amplifier technologies and as a data pathfinder in the $5 - 25$ GHz range ($\sim20-100\: \mu$eV). The platform is small but flexible to facilitate the development of new microwave cavity and amplifier concepts in an operational environment. The experiment has recently completed its first data production; it is the first microwave cavity axion search to deploy a Josephson parametric amplifier and a dilution refrigerator to achieve near-quantum limited performance., Comment: 17 pages, published in NIM A. v2: added changes made during the review process

We report on the first results from a new microwave cavity search for dark matter axions with masses above $20~\mu\text{eV}$. We exclude axion models with two-photon coupling $g_{a\gamma\gamma} \gtrsim 2\times10^{-14}~\text{GeV}^{-1}$ over the range $23.55~\mu\text{eV} < m_a < 24.0~\mu\text{eV}$. These results represent two important achievements. First, we have reached cosmologically relevant sensitivity an order of magnitude higher in mass than any existing limits. Second, by incorporating a dilution refrigerator and Josephson parametric amplifier, we have demonstrated total noise approaching the standard quantum limit for the first time in an axion search., Comment: 5 pages, 3 figures, accepted for publication in PRL. v2: added changes made during the review process

The axion is a light pseudoscalar particle which suppresses CP-violating effects in strong interactions and also happens to be an excellent dark matter candidate. Axions constituting the dark matter halo of our galaxy may be detected by their resonant conversion to photons in a microwave cavity permeated by a magnetic field. The current generation of the microwave cavity experiment has demonstrated sensitivity to plausible axion models, and upgrades in progress should achieve the sensitivity required for a definitive search, at least for low mass axions. However, a comprehensive strategy for scanning the entire mass range, from 1-1000 $\mu$eV, will require significant technological advances to maintain the needed sensitivity at higher frequencies. Such advances could include sub-quantum-limited amplifiers based on squeezed vacuum states, bolometers, and/or superconducting microwave cavities. The Axion Dark Matter eXperiment at High Frequencies (ADMX-HF) represents both a pathfinder for first data in the 20-100 $\mu$eV range ($\sim$5-25 GHz), and an innovation test-bed for these concepts.

We show that at higher frequencies, and thus higher axion masses, single-photon detectors become competitive and ultimately favored, when compared to quantum-limited linear amplifiers, as the detector technology in microwave cavity experimental searches for galactic halo dark matter axions. The cross-over point in this comparison is of order 10 GHz ($\sim 40\ \mu$eV), not far above the frequencies of current searches., Comment: 5 pages, 1 figure new version address comments received

A description is presented of apparatus used to carry out an experimental search for an electric dipole moment of the neutron, at the Institut Laue-Langevin (ILL), Grenoble. The experiment incorporated a cohabiting atomic-mercury magnetometer in order to reduce spurious signals from magnetic field fluctuations. The result has been published in an earlier letter; here, the methods and equipment used are discussed in detail.

We have performed high precision experimental measurements of spin precession using a dressed $^3$He atomic beam. Spin-dressing uses an oscillating magnetic field detuned to high frequency which is orthogonal to a static magnetic field to effectively change the gyromagnetic ratio of a spin. We verify the validity of the spin-dressing Hamiltonian in regions beyond the limiting solution in which the Larmor frequency is much smaller than the frequency of the dressing field. We also evaluate the effect of magnetic field misalignment, e.g. if the oscillating magnetic field is not orthogonal to the static magnetic field. Modulation of the dressing field parameters is also discussed, with a focus on whether such a modulation can be approximated merely as a time dependent, dressed gyromagnetic ratio. Furthermore, we discuss implications for a proposed search for the neutron electric dipole moment, which would employ spin-dressing to make the effective $^3$He and neutron magnetic moments equal., Comment: 10 pages, 7 figures

We report on the results of a search for the electron electric dipole moment $d_e$ using paramagnetic ferroelectric Eu$_{0.5}$Ba$_{0.5}$TiO$_3$. The electric polarization creates an effective electric field that makes it energetically favorable for the spins of the seven unpaired $4f$ electrons of the Eu$^{2+}$ to orient along the polarization, provided that $d_e\neq 0$. This interaction gives rise to sample magnetization, correlated with its electric polarization, and is therefore equivalent to a linear magnetoelectric effect. A SQUID magnetometer is used to search for the resulting magnetization. We obtain $d_e = (-1.07\pm3.06_\text{stat}\pm 1.74_\text{sys})\times10^{-25}\ecm$, implying an upper limit of $|d_e|<6.05\times10^{-25}\ecm$ (90% confidence)., Comment: 5 pages, 4 figures

We report measurements of the short-range forces between two macroscopic gold-coated plates using a torsion pendulum. The force is measured for separations between 0.7 $\mu$m and 7 $\mu$m, and is well described by a combination of the Casimir force, including the finite-temperature correction, and an electrostatic force due to patch potentials on the plate surfaces. We use our data to place constraints on the Yukawa-type "new" forces predicted by theories with extra dimensions. We establish a new best bound for force ranges 0.4 $\mu$m to 4 $\mu$m, and, for forces mediated by gauge bosons propagating in $(4+n)$ dimensions and coupling to the baryon number, extract a $(4+n)$-dimensional Planck scale lower limit of $M_*>70$ TeV., Comment: 4 pages, 2 figures

A number of experimental measurements of the Casimir force have observed a logarithmic distance variation of the voltage that minimizes electrostatic force between the plates in a sphere-plane geometry. We show that this variation can be simply understood from a geometric averaging of surface potential patches together with the Proximity Force Approximation., Comment: 5 pages

The imperfect termination of static electric fields at semiconducting surfaces has been long known in solid state and transistor physics. We show that the imperfect shielding leads to an offset in the distance between two surfaces as determined by electrostatic force measurements. The effect exists even in the case of good conductors (metals) albeit much reduced., Comment: 7 pages, 2 figures

We report results of an experimental search for the intrinsic Electric Dipole Moment (EDM) of the electron using a solid-state technique. The experiment employs a paramagnetic, insulating gadolinium gallium garnet (GGG) that has a large magnetic response at low temperatures. The presence of the eEDM would lead to a small but non-zero magnetization as the GGG sample is subject to a strong electric field. We search for the resulting Stark-induced magnetization with a sensitive magnetometer. Recent progress on the suppression of several sources of background allows the experiment to run free of spurious signals at the level of the statistical uncertainties. We report our first limit on the eEDM of $(-5.57 \pm 7.98 \pm 0.12)\times$10$^{-25}$e$\cdot$cm with 5 days of data averaging., Comment: 9 pages, 9 figures, Revtex 4.1

Quantum theory predicts the existence of the Casimir force between macroscopic bodies, due to the zero-point energy of electromagnetic field modes around them. This quantum fluctuation-induced force has been experimentally observed for metallic and semiconducting bodies, although the measurements to date have been unable to clearly settle the question of the correct low-frequency form of the dielectric constant dispersion (the Drude model or the plasma model) to be used for calculating the Casimir forces. At finite temperature a thermal Casimir force, due to thermal, rather than quantum, fluctuations of the electromagnetic field, has been theoretically predicted long ago. Here we report the experimental observation of the thermal Casimir force between two gold plates. We measured the attractive force between a flat and a spherical plate for separations between 0.7 $\mu$m and 7 $\mu$m. An electrostatic force caused by potential patches on the plates' surfaces is included in the analysis. The experimental results are in excellent agreement (reduced $\chi^2$ of 1.04) with the Casimir force calculated using the Drude model, including the T=300 K thermal force, which dominates over the quantum fluctuation-induced force at separations greater than 3 $\mu$m. The plasma model result is excluded in the measured separation range., Comment: 6 pages

A new systematic correction for Casimir force measurements is proposed and applied to the results of an experiment that was performed more than a decade ago. This correction brings the experimental results into good agreement with the Drude model of the metallic plates' permittivity. The systematic is due to time-dependent fluctuations in the distance between the plates caused by mechanical vibrations or tilt, or position measurement uncertainty, and is similar to the correction for plate roughness., Comment: 8 pages, one figure

We describe a quantum cryptography protocol with up to twenty four-dimensional ($\mathcal{D} =4$) states generated by a polarization-, phase- and time-encoding transmitter. This protocol can be experimentally realized with existing technology, drawing from time-encoded and polarization-encoded systems. The protocol is error tolerant and has a quantum bit-rate of 2 per transmission/detection, which when combined with state detection efficiency yields a qubit efficiency of up to 1 or double that of BB84-{\it like} protocols., Comment: New title, 6 pages, 3 figures. Submitted to PRL: 12/23/09. Includes PRL response. Possible it will not be published in PRL; PRA next likely. Nominally related to arXiv:0808.0686, but uniquely different. Tell us (buttler@lanl.gov) if you find an error.

We describe the first-principles design and subsequent synthesis of a new material with the specific functionalities required for a solid-state-based search for the permanent electric dipole moment of the electron. We show computationally that perovskite-structure europium barium titanate should exhibit the required large and pressure-dependent ferroelectric polarization, local magnetic moments, and absence of magnetic ordering even at liquid helium temperature. Subsequent synthesis and characterization of Eu$_{0.5}$Ba$_{0.5}$TiO$_3$ ceramics confirm the predicted desirable properties., Comment: Nature Materials, in press

In a recent paper, Wicht, L\"ammerzahl, Lorek, and Dittus [Phys. Rev. {\bf A 78}, 013610 (2008)] come to the conclusion that a molecular rotational-vibrational quantum interferometer may possess the sensitivity necessary to detect gravitational waves. We do not agree with their results and demonstrate here that the true sensitivity of such interferometer is many orders of magnitude worse than that claimed in the mentioned paper. In the present comment we estimate the expected energy shifts and derive equations of motion for a quantum symmetric top (diatomic molecule or deformed nucleus) in the field of gravitational wave, and then estimate the sensitivity of possible experiments., Comment: extended version

We propose to use ferroelectric (Eu,Ba)TiO$_3$ ceramics just above their magnetic ordering temperature for a sensitive electron electric dipole moment search. We have synthesized a number of such ceramics with various Eu concentrations and measured their properties relevant for such a search: permeability, magnetization noise, and ferroelectric hysteresis loops. The results of our measurements indicate that a search for the electron electric dipole moment with Eu$_{0.5}$Ba$_{0.5}$TiO$_3$ should lead to an order of magnitude improvement on the current best limit.

We present calculations of contact potential surface patch effects that simplify previous treatments. It is shown that, because of the linearity of Laplace's equation, the presence of patch potentials does not affect an electrostatic calibration (of force and/or distance) of a two-plate Casimir measurement apparatus. Using models that include long-range variations in the contact potential across the plate surfaces, a number of experimental observations can be reproduced and explained. For these models, numerical calculations show that if a voltage is applied between the plates which minimizes the force, a residual electrostatic force persists, and that the minimizing potential varies with distance. The residual force can be described by a fit to a simple two-parameter function involving the minimizing potential and its variation with distance. We show the origin of this residual force by use of a simple parallel capacitor model. Finally, the implications of a residual force that varies in a manner different from 1/d on the accuracy of previous Casimir measurements is discussed., Comment: Final version, accepted by Phys. Rev. A

The neutron beta-decay lifetime plays an important role both in understanding weak interactions within the framework of the Standard Model and in theoretical predictions of the primordial abundance of 4He in Big Bang Nucleosynthesis. In previous work, we successfully demonstrated the trapping of ultracold neutrons (UCN) in a conservative potential magnetic trap. A major upgrade of the apparatus is nearing completion at the National Institute of Standards and Technology Center for Neutron Research (NCNR). In our approach, a beam of 0.89 nm neutrons is incident on a superfluid 4He target within the minimum field region of an Ioffe-type magnetic trap. A fraction of the neutrons is downscattered in the helium to energies <200 neV, and those in the appropriate spin state become trapped. The inverse process is suppressed by the low phonon density of helium at temperatures less than 200 mK, allowing the neutron to travel undisturbed. When the neutron decays the energetic electron ionizes the helium, producing scintillation light that is detected using photomultiplier tubes. Statistical limitations of the previous apparatus will be alleviated by significant increases in field strength and trap volume resulting in twenty times more trapped neutrons., Comment: 5 pages, 5 figures

We have measured the short-range attractive force between crystalline Ge plates, and found contributions from both the Casimir force and an electrical force possibly generated by surface patch potentials. Using a model of surface patch effects that generates an additional force due to a distance dependence of the apparent contact potential, the electrical force was parameterized using data at distances where the Casimir force is relatively small. Extrapolating this model, to provide a correction to the measured force at distances less than 5 $\mu$m, shows a residual force that is in agreement, within experimental uncertainty, with five models that have been used to calculate the Casimir force., Comment: 5 pages and 4 figures, version 2

Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, $\alpha$. The data provide a rate of fractional temporal variation of $\alpha$ of $(-2.4\pm2.3)\times10^{-15}$ yr$^{-1}$ or a value of $(-7.8 \pm 5.9) \times 10^{-6}$ for $k_\alpha$, the variation coefficient for $\alpha$ in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium., Comment: 10 pages, 6 figures, fixed typos in section 5, updated results

The next generation of particle edm searches will be at such a high sensitivity that it will be possible for the results to be contaminated by a systematic error resulting from the interaction of the motional (E x v/c) magnetic field with stray field gradients. In this paper we extend previous work to present an analytic form for the frequency shift in the case of a rectangular storage vessel and discuss the implications of the result for the neutron edm experiment which will be installed at the SNS (Spallation Neutron Source) by the LANL collaboration, Comment: 10 pages, 7 figures New version: improved description of physicalidea, updated author list, replaced defective figure files

We study the magnetic properties of Gadolinium-Yttrium Iron Garnet ($\text{Gd}_{x}\text{Y}_{3-x}\text{Fe}_5\text{0}_{12}$, $x=3,1.8$) ferrite ceramics. The complex initial permeability is measured in the temperature range 2 K to 295 K at frequency of 1 kHz, and in the frequency range 100 Hz to 200 MHz at temperatures 4 K, 77 K, and 295 K. The magnetic viscosity-induced imaginary part of the permeability is observed at low frequencies. Measurements of the magnetization noise are made at 4 K. Using the fluctuation-dissipation theorem, we find that the observed magnetization fluctuations are consistent with our measurements of the low-frequency imaginary part of permeability. We discuss some implications for proposed precision measurements as well as other possible applications.

We address a number of issues regarding solid state electron electric dipole moment (EDM) experiments, focusing on gadolinium iron garnet (abbreviated GdIG, chemical formula Gd$_3$Fe$_5$O$_{12}$) as a possible sample material. GdIG maintains its high magnetic susceptibility down to 4.2 K, which enhances the EDM-induced magnetization of a sample placed in an electric field. We estimate that lattice polarizability gives rise to an EDM enhancement factor of approximately 20. We also calculate the effect of the demagnetizing field for various sample geometries and permeabilities. Measurements of intrinsic GdIG magnetization noise are presented, and the fluctuation-dissipation theorem is used to compare our data with the measurements of the imaginary part of GdIG permeability at 4.2 K, showing good agreement above frequencies of a few hertz. We also observe how the demagnetizing field suppresses the noise-induced magnetic flux, confirming our calculations. The statistical sensitivity of an EDM search based on a solid GdIG sample is estimated to be on the same level as the present experimental limit. Such a measurement would be valuable, given the completely different methods and systematics involved. The most significant systematics in such an experiment are the magnetic hysteresis and the magneto-electric effect. Our analysis shows that it should be possible to control these at the level of statistical sensitivity.

We develop and present a quantum cryptography concept in which phase determinations are made from the time that a photon is detected, as opposed to where the photon is detected, and hence is a non-interferometric process. The phase-encoded quantum information is contained in temporal and polarization superpositions of single photon states, forming a complex qudit of Hilbert dimension D equal to or greater than 4. Based on this, we have developed a new quantum key distribution protocol that allows the generation of secret key in the presence of higher noise than is possible with other protocols., Comment: Submitted to PRL May 1, 2008 4 pages, 2 figures

The role of 3He-3He collisions in our diffusion experiment is addressed and shown to not be relevant to the measurement of 3He diffusion against phonons in superfluid helium., Comment: Two pages, in Europhysics Letters format

Radio-frequency E1 transitions between nearly degenerate, opposite parity levels of atomic dysprosium were monitored over an eight month period to search for a variation in the fine-structure constant. During this time period, data were taken at different points in the gravitational potential of the Sun. The data are fitted to the variation in the gravitational potential yielding a value of $(-8.7 \pm 6.6) \times 10^{-6}$ for the fit parameter $k_\alpha$. This value gives the current best laboratory limit. In addition, our value of $k_{\alpha}$ combined with other experimental constraints is used to extract the first limits on k_e and k_q. These coefficients characterize the variation of m_e/m_p and m_q/m_p in a changing gravitational potential, where m_e, m_p, and m_q are electron, proton, and quark masses. The results are $k_e = (4.9 \pm 3.9) \times 10^{-5}$ and $k_q = (6.6 \pm 5.2) \times 10^{-5}$., Comment: 6 pages, 3 figures

We report a measurement of dressed-spin effects of polarized 3He atoms from a cold atomic source traversing a region of constant magnetic field B0 and a transverse oscillatory dressing field Bd cos(omega * t). The observed effects are compared with a numerical simulation using the Bloch equation as well as a calculation based on the dressed-atom formalism. An application of the dressed spin of 3He for a proposed neutron electric dipole moment measurement is also discussed., Comment: 4 pages, 5 figures, REVTex4, submitted to PRL

We reanalyze Oklo $^{149}$Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of $\alpha$, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the $^{149}$Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient $^{149}$Sm effective cross sections, and use these values to set limits on the time-variation of $\alpha$. Our study resolves a contradictory situation with previous Oklo $\alpha$-results. Our suggested $2 \sigma$ bound on a possible time variation of $\alpha$ over two billion years is stringent: $ -0.24 \times 10^{-7} \le \frac{\Delta \alpha}{\alpha} \le 0.11 \times 10^{-7}$, but model dependent in that it assumes only $\alpha$ has varied over time., Comment: 14 pages, 4 figures. Corrections: minus sign missing in equation 32, changed sign of change in alpha in equations 33 and 34. Also added two new references and corrected minor typographical errors

We point out that the rotation of the Earth leads to a non-negligible apparent electric-dipole moment effect for this experiment., Comment: 2 pages, no figures The manuscript has been modified (11 Oct 2007) to take into account the initial response from the authors, to shorten the mansuscript, and to clarify the relevance of the effect

Over a period of eight months, we have monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These transition frequencies are highly sensitive to temporal variation of the fine-structure constant ($\alpha$) due to relativistic corrections of large and opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf) electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in $^{163}$Dy and the 235-MHz transition in $^{162}$Dy are 9.0$\pm$6.7 Hz/yr and -0.6$\pm$6.5 Hz/yr, respectively. These results provide a value for the rate of fractional variation of $\alpha$ of $(-2.7\pm2.6)\times 10^{-15}$ yr$^{-1}$ (1 $\sigma$) without any assumptions on the constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity., Comment: 4 pages, 2 figures

The search for particle electric dipole moments (edm) represents a most promising way to search for physics beyond the standard model. A number of groups are planning a new generation of experiments using stored gases of various kinds. In order to achieve the target sensitivities it will be necessary to deal with the systematic error resulting from the interaction of the well-known $\overrightarrow{v}\times \overrightarrow{E}$ field with magnetic field gradients (often referred to as the geometric phase effect (Commins, ED; Am. J. Phys. \QTR{bf}{59}, 1077 (1991), Pendlebury, JM \QTR{em}{et al;} Phys. Rev. \QTR{bf}{A70}, 032102 (2004)). This interaction produces a frequency shift linear in the electric field, mimicking an edm. In this work we introduce an analytic form for the velocity auto-correlation function which determines the velocity-position correlation function which in turn determines the behavior of the frequency shift (Lamoreaux, SK and Golub, R; Phys. Rev \QTR{bf}{A71}, 032104 (2005)) and show how it depends on the operating conditions of the experiment. We also discuss some additional issues., Comment: 21 pages, 5 figures

A new search for a permanent electric dipole moment (EDM) of the neutron is underway using ultracold neutrons produced and held in a bath of superfluid helium. Attaining the target sensitivity requires maintaining an electric field of several tens of kilovolts per centimeter across the experimental cell, which is nominally 7.5 cm wide and will contain about 4 liters of superfluid. The electrical properties of liquid helium are expected to be sufficient to meet the design goals, but little is known about these properties for volumes and electrode spacings appropriate to the EDM experiment. Furthermore, direct application of the necessary voltages from an external source to the experimental test cell is impractical. An apparatus to amplify voltages in the liquid helium environment and to test the electrical properties of the liquid for large volumes and electrode spacings has been constructed. The device consists of a large-area parallel plate capacitor immersed in a 200 liter liquid helium dewar. Preliminary results show the breakdown strength of normal state liquid helium is at least 90 kV/cm at these volumes, at the helium vapor pressure corresponding to 4.38 K. These fields hold for more than 11 hours with leakage currents less than 170 pA (about 20% of the maximum tolerable in the EDM experiment). The system is also found to be robust against anticipated radiation backgrounds. Preliminary results for superfluid show that fields of at least 30 kV/cm can be sustained at the volumes required for the EDM experiment, about 60% of the design goal. These results are likely limited by the low pressure that must be maintained above the superfluid bath., Comment: 29 pages, 15 figures

The search for particle electric dipole moments represents a most promising way to search for physics beyond the standard model. A number of groups are planning a new generation of experiments using stored gases of various kinds. In order to achieve the target sensitivities it will be necessary to deal with the systematic error resulting from the interaction of the well-known E x v field with magnetic field gradients (often referred to as the geometric phase effect [9,10]). This interaction produces a frequency shift linear in the electric field, mimicking an edm. In this work we introduce an analytic model for the correlation function which determines the behavior of the frequency shift [11], and show in detail how it depends on the operating conditions of the experiment. We also propose a method to directly measure ths correlation function under the exact conditions of a given experiment., Comment: 18 pages,13 figures, updated reference 17, replaced figures with postscript

Experiments searching for parity- and time-reversal-invariance-violating effects that rely on measuring magnetization of a condensed-matter sample induced by application of an electric field are considered. A limit on statistical sensitivity arises due to random fluctuations of the spins in the sample. The scaling of this limit with the number of spins and their relaxation time is derived. Application to an experiment searching for nuclear Schiff moment in a ferroelectric is discussed., Comment: 6 pages, no figures