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DOE OSTI2025

Multi-qubit nanoscale sensing with entanglement as a resource

Nitrogen vacancy (NV) centres in diamond are widely deployed as local magnetic sensors, using single-qubit control to measure both time-averaged fields and noise with nanoscale spatial resolution. Moving beyond single qubits to multi-qubit control enables new sensing modalities such as measuring nonlocal spatiotemporal correlators or using entangled states to enhance measurement sensitivity. Here, in this work, we describe protocols for using optically unresolved NV centre pairs and nuclear spins as multi-qubit sensors for measuring correlated noise at nanometre length scales. For noninteracting NV centres, we implement a phase-cycling protocol that disambiguates magnetic correlations from variance fluctuations, leveraging the presence of a third qubit, a 13 C nucleus, to effect coherent single-NV spin flips and enable phase cycling even for co-aligned NV centres that are spectrally unresolved. For length scales around 10 nm, we create maximally entangled Bell states through dipole–dipole coupling between two NV centres and use these entangled states to directly read out the magnetic field correlation, rather than reconstructing it from independent measurements of unentangled NV centres. Importantly, this changes the scaling of sensitivity with readout noise from quadratic to linear. For conventional off-resonant readout of the NV centre spin state (for which the readout noise is roughly 30 times the quantum projection limit), this results in more than an order of magnitude improvement in sensitivity. Finally, we demonstrate methods for detecting high spatial- and temporal-resolution correlators with pairs of strongly interacting NV centres.

condensed-matter physics↗

NASA NTRS1974

The motion of a proton in the equatorial magnetosphere

A proton of low energy moving in the equatorial plane of the earth will experience drift motions due to both the magnetic field (magnetic gradient drift only, if the field is assumed to be that of a dipole) and the electric field. The electric drift again separates into two parts - the drift due to the main electric field (or convection electric field) existing in the frame of the earth, and that due to the earth's rotation. One result indicated by this work is that at distances of 4 - 6 earth radii, a transition from trapped proton orbits to open trajectories leading to the tail occurs at about 10 kev, the precise value depending upon local time. Such a transition also seems to be indicated by particle observations using Explorer 45. The energy spectrum (at magnetically quiet times) of equatorial protons above this energy can be explained by charge exchange but increased flux observed below it seems to be related to the influx of particles on open orbits from the tail.

Stern, D. P.↗

DOE OSTI2014

Theoretical estimates of the anapole magnetizabilities of C{sub 4}H{sub 4}X{sub 2} cyclic molecules for X=O, S, Se, and Te

Calculations have been carried out for C{sub 4}H{sub 4}X{sub 2} cyclic molecules, with X=O, S, Se, and Te, characterized by the presence of magnetic-field induced toroidal electron currents and associated orbital anapole moments. The orbital anapole induced by a static nonuniform magnetic field B, with uniform curl C=∇×B, is rationalized via a second-rank anapole magnetizability tensor a{sub αβ}, defined as minus the second derivative of the second-order interaction energy with respect to the components C{sub α} and B{sub β}. The average anapole magnetizability a{sup ¯} equals −χ{sup ¯}, the pseudoscalar obtained by spatial averaging of the dipole-quadrupole magnetizability χ{sub α,βγ}. It has different sign for D and L enantiomeric systems and can therefore be used for chiral discrimination. Therefore, in an isotropic chiral medium, a homogeneous magnetic field induces an electronic anapole A{sub α}, having the same magnitude, but opposite sign, for two enantiomorphs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Mössbauer investigations of hyperfine interactions features of {sup 57}Fe nuclei in BiFeO{sub 3} ferrite

New results of {sup 57}Fe Mössbauer studies on BiFeO{sub 3} powder sample performed at various temperatures above and below magnetic phase transitions point T{sub N} ≈ 640K are reported. We have performed self-consistent calculations of the lattice contributions to the EFG tensor, taking into account dipole moments of the O{sup 2−} and Bi{sup 3+} ions. Low-temperature {sup 57}Fe Mössbauer spectra recorded at T < T{sub N} were analyzed assuming an anharmonic cycloidal modulation of the Fe{sup 3+} magnetic moments. The cycloidal modulation of the iron spin was described with the elliptic Jacobi function sn[(±4K(m)/λ)x,m]. The good fit of the experimental spectra was obtained for the anharmonicity m = 0.44 ± 0.04 (T = 4.9K) resulting from the easy-axis magnetic anisotropy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1979

The magnetic field of Mercury

The paper examines the magnetic field observations and their analyses relating to the determination of the Mercury magnetic field. Methods of analyzing data included: (1) comparison of bow shock and magnetopause relative positions at Mercury to the earth, (2) direct spherical harmonic analysis, (3) magnetosphere modeling by an image dipole, and (4) scaling of a mathematical model for the terrestrial magnetosphere. Dipole moments were determined using partial quadrupole and octupole terms to improve the least-square fit of models to observations; analyses by method (2) yield a convergent series of dipole moments values considered to best represent the intrinsic planetary field. Finally, it is suggested that the origin of the magnetic field of Mercury cannot be uniquely determined, but the sources of convective energy may be radiogenic decay and heat release, gravitational settling, and differentiation of processional torques.

Ness, N. F.↗

DOE OSTI2014

Investigation on the pyroelectric property of polycrystalline GdMnO{sub 3}

Pyroelectric property of orthorhomic GdMnO{sub 3} polycrystalline samples was investigated. Two pyrocurrent peaks were observed with the sharp one near 20 K and the broad one at around 120 K. The dependences of these two peaks on magnetic field, heating rate, and poling voltage were explored systematically. The sharp peak is related to the ferroelectric transition, while the behavior of the broad one corresponds to dipole reorientation. Some key pyroelectric features are proposed to separate the spin-induced ferroelectricity from other effects. This work is helpful for understanding the pyroelectric property of multiferroic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2017

Magnetar Broadband X-Ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE

The 1–70 keV persistent spectra of 15 magnetars, observed with Suzaku from 2006 to 2013, were studied as a complete sample. Combined with early NuSTAR observations of four hard X-ray emitters, nine objects showed a hard power-law emission dominating at ≳10 keV with the 15–60 keV flux of ∼1–11×10{sup −11} erg s{sup −1} cm{sup −2}. The hard X-ray luminosity L{sub h}, relative to that of a soft-thermal surface radiation L{sub s}, tends to become higher toward younger and strongly magnetized objects. Their hardness ratio, updated from a previous study and defined as ξ=L{sub h}/L{sub s}, is correlated with the measured spin-down rate P-dot as ξ=0.62×( P-dot /10{sup −11}ss{sup −1}){sup 0.72}, corresponding to positive and negative correlations with the dipole field strength B{sub d} (ξ∝B{sub d}{sup 1.41}) and the characteristic age τ{sub c} (ξ∝τ{sub c}{sup −0.68}), respectively. Among our sample, five transients were observed during X-ray outbursts, and the results are compared with their long-term 1–10 keV flux decays monitored with Swift/XRT and RXTE/PCA. Fading curves of three bright outbursts are approximated by an empirical formula used in the seismology, showing a ∼10–40 day plateau phase. Transients show the maximum luminosities of L{sub s} ∼ 10{sup 35} erg s{sup −1}, which are comparable to those of persistently bright ones, and fade back to ≲10{sup 32} erg s{sup −1}. Spectral properties are discussed in the framework of the magnetar hypothesis.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1994

Method for confining the magnetic field of the cross-tail current inside the magnetopause

A method is presented for analytically representing the magnetic field due to the cross-tail current and its closure on the magnetopause. It is an extension of a method used by Tsyganenko (1989b) to confine the dipole field inside an ellipsoidal magnetopause using a scalar potential. Given a model of the cross-tail current, the implied net magnetic field is obtained by adding to the cross-tail current field a potential field B = - del gamma, which makes all field lines divide into two disjoint groups, separated by the magnetopause (i.e., the combined field is made to have zero normal component with the magnetopause). The magnetopause is assumed to be an ellipsoid of revolution (a prolate spheroid) as an approximation to observations (Sibeck et al., 1991). This assumption permits the potential gamma to be expressed in spheroidal coordinates, expanded in spheroidal harmonics and its terms evaluated by performing inversion integrals. Finally, the field outside the magnetopause is replaced by zero, resulting in a consistent current closure along the magnetopause. This procedure can also be used to confine the modeled field of any other interior magnetic source, though the model current must always flow in closed circuits. The method is demonstrated on the T87 cross-tail current, examples illustrate the effect of changing the size and shape of the prescribed magnetopause and a comparison is made to an independent numerical scheme based on the Biot-Savart equation.

Sotirelis, T.↗

NASA NTRS1981

Jovian magnetic models and the polarization angle of Jovian decimetric radiation

A comparative study of the direction of linear polarization of Jovian decimetric (synchrotron) radiation as measured astronomically and as determined from a model of the inner Jovian magnetosphere is discussed. It is noted that the model depicts the radiation as coming from rings of relativistic electrons in the Jovimagnetic equator at varying radial distances from the center of the planet. The equator is determined through each of two magnetic representations - the O4 model of Acuna and Ness (1976) and the P10-11 model of Smith et al. (1976) - derived from in situ Pioneer magnetometer measurements. Deviations from a (planar) dipole equator are found to occur at nearly all longitudes in both models; no evidence is found for a longitudinally localized magnetic anomaly.

Birmingham, T. J.↗

DOE OSTI2022

The effect of polymer stiffness on magnetization reversal of magnetorheological elastomers

Ultrasoft magnetorheological elastomers (MREs) offer convenient real-time magnetic field control of mechanical properties that provides a means to mimic mechanical cues and regulators of cells in vitro. Here, we systematically investigate the effect of polymer stiffness on magnetization reversal of MREs using a combination of magnetometry measurements and computational modeling. Poly-dimethylsiloxane-based MREs with Young’s moduli that range over two orders of magnitude were synthesized using commercial polymers Sylgard™ 527, Sylgard 184, and carbonyl iron powder. The magnetic hysteresis loops of the softer MREs exhibit a characteristic pinched loop shape with almost zero remanence and loop widening at intermediate fields that monotonically decreases with increasing polymer stiffness. A simple two-dipole model that incorporates magneto-mechanical coupling not only confirms that micrometer-scale particle motion along the applied magnetic field direction plays a defining role in the magnetic hysteresis of ultrasoft MREs but also reproduces the observed loop shapes and widening trends for MREs with varying polymer stiffnesses.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Creating a three-dimensional intrinsic electric dipole on rotated CrI 3 bilayers

Here two-dimensional (2D) materials are being explored as a novel multiferroic platform. One of the most studied magnetoelectric multiferroic 2D materials are antiferromagnetically coupled (AFM) CrI 3 bilayers. Neglecting magnetism, those bilayers possess a crystalline point of inversion, which is only removed by the antiparallel spin configuration among its two constituent monolayers. The resulting intrinsic electric dipole on those bilayers has a magnitude no larger than 0.04 pC/m, it points out of plane, and it reverts direction when the Ising-like-chromium spins are flipped (toward opposite layers versus away from opposite layers). The combined presence of antiferromagnetism and a weak intrinsic electric dipole makes this material a two-dimensional magnetoelectric multiferroic. Here, we remove the crystalline center of inversion of the bilayer by a relative 60° rotation of its constituent monolayers. This process enhances the out-of-plane intrinsic electric dipole tenfold with respect to its magnitude in the nonrotated AFM bilayer and also creates an even stronger and switchable in-plane intrinsic electric dipole. The ability to create a three-dimensional electric dipole is important because it enhances the magnetoelectric coupling on this experimentally accessible 2D material, which is explicitly calculated here as well.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Spin polarization transfer by the radical pair mechanism

In a three-site representation, we study a spin polarization transfer from radical pair spins to a nearby electron or nuclear spin. The quantum dynamics of the radical pair spins is governed by a constant exchange interaction between the radical pair spins which have different Zeeman frequencies. Radical pair spins can recombine to the singlet ground state or to lower energy triplet states. It is then shown that the coherent dynamics of the radical pair induces spin polarization on the nearby third spin in the presence of a magnetic field. The spin polarization transfer depends on the difference between Zeeman frequencies, the singlet and triplet recombination rates, and on the exchange and dipole-dipole interactions between the different spins. In particular, the sign of the polarization depends on the exchange coupling between radical pair spins and also on the difference between singlet and triplet recombination rate constants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1979

The synchronous orbit magnetic field data set

The magnetic field at synchronous orbit is the result of superposition of fields from many sources such as the earth, the magnetopause, the geomagnetic tail, the ring current and field-aligned currents. In addition, seasonal changes in the orientation of the earth's dipole axis causes significant changes in each of the external sources. Main reasons for which the synchronous orbit magnetic field data set is a potentially valuable resource are outlined. The primary reason why synchronous magnetic field data have not been used more extensively in magnetic field modeling is the presence of absolute errors in the measured fields. Nevertheless, there exists a reasonably large collection of synchronous orbit magnetic field data. Some of these data can be useful in quantitative modeling of the earth's magnetic field. A brief description is given of the spacecraft, the magnetometers, the standard graphical data displays, and the digital data files.

Mcpherron, R. L.↗

DOE OSTI2016

Beam line shielding calculations for an Electron Accelerator Mo-99 production facility

The purpose of this study is to evaluate the photon and neutron fields in and around the latest beam line design for the Mo-99 production facility. The radiation dose to the beam line components (quadrupoles, dipoles, beam stops and the linear accelerator) are calculated in the present report. The beam line design assumes placement of two cameras: infra red (IR) and optical transition radiation (OTR) for continuous monitoring of the beam spot on target during irradiation. The cameras will be placed off the beam axis offset in vertical direction. We explored typical shielding arrangements for the cameras and report the resulting neutron and photon dose fields.

43 PARTICLE ACCELERATORS↗

NASA NTRS1987

The magnetic field of Uranus

Aspherical harmonic model of the planetary magnetic field of Uranus is obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems. The Goddard Space Flight Center 'Q3' model is characterized by a large dipole tilt (58.6 deg) relative to the rotation axis, a dipole moment of 0.228 G R(Uranus radii cubed) and an unusually large quadrupole moment. Characteristics of this complex model magnetic field are illustrated using contour maps of the field on the planet's surface and discussed in the context of possible dynamo generation in the relatively poorly conducting 'ice' mantle.

Connerney, J. E. P.↗

DOE OSTI2014

nEDM at SNS

This PowerPoint presentation covered the following topics: Overview; participants in the collaboration; the experimental method and Free Precession Method descriptions; and then experimental design elements, ending with a summary. A new nEDM experiment is under development with a goal sensitivity 90% CL σ d < (3-5) x 10 -28 e-cm in 300 live-days; Free precession method: SQUIDS to read out the 3 He precession frequency, Scintillation signal for the n relative precession frequency; Dressed spin method: Strong RF field to match n and 3 He effective magnetic moments; Modulation/feedback of dressing parameter based on scintillation signal; and, Ongoing development/demonstration of many aspects of the apparatus (a subset was shown here).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1973

TRW plasma wave experiment for the IMP-H mission

The IMP-H plasma wave experiment is designed to extend knowledge of wave-particle interactions in the disturbed cislunar region, the distant geomagnetic tail, the upstream solar wind, and the flanks of the magnetosheath-shock interface. It is expected to identify plasma instabilities, study particle acceleration and heating at collisionless shocks and other discontinuities, analyze turbulent conductivity and field line merging, and provide new information on dissipation processes for suprathermal particles. Instrumentation for the plasma wave experiment is designed to measure local electric and magnetic field oscillations over the frequency range 10 Hz to 100 kHz. A 24 inch electric dipole, a 7 inch diameter air core search coil, and the associated preamplifiers are mounted on a spacecraft counterweight boom. The frequency range of 10 Hz to 100 kHz for both E and B is processed using an eight-channel spectrum analyzer located in the instrument main-body package (a standard IMP trapezoidal module, 3 inches high). Electric fields as small as 10-100 microvolts/meter and magnetic signals as small as 1-3 milligamma will be detected.

Virobik, P. F.↗

DOE OSTI2023

Design and Assembly of a Large-Aperture Nb 3 Sn Cos-Theta Dipole Coil With Stress Management in Dipole Mirror Configuration

The stress-management cos-theta (SMCT) coil is a new concept which has been proposed and is being developed at Fermilab in the framework of US Magnet Development Program (US-MDP) for high-field and/or large-aperture accelerator magnets based on low-temperature and high-temperature superconductors. The SMCT structure is used to reduce large coil deformations under the Lorentz forces and, thus, the excessively large strains and stresses in the coil. A large-aperture Nb 3 Sn SMCT dipole coil has been developed and fabricated at Fermilab to demonstrate and test the SMCT concept including coil design, fabrication technology and performance. The first SMCT coil has been assembled with 60-mm aperture Nb 3 Sn coil inside a dipole mirror configuration and will be tested separately and in series with the insert coil. Here this paper summarizes the large-aperture SMCT coil design and parameters and reports the coil fabrication steps and its assembly in dipole mirror configuration.

43 PARTICLE ACCELERATORS↗