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We present and analyze a method of laser-frequency stabilization via steady-state patterns of spectral holes in Eu3+:Y2SiO5. Three regions of spectral holes are created, spaced in frequency by the ground-state hyperfine splittings of 151Eu3+. The absorption pattern is shown not to degrade after days of laser-frequency stabilization. An optical frequency comparison of a laser locked to such a steady-state spectral-hole pattern with an independent cavity-stabilized laser and a Yb optical lattice clock demonstrates a spectral-hole fractional frequency instability of 1.0 × 10-15τ-1/2 that averages to 8.5+4.8-1.8 × 10-17 at τ = 73 s. Residual amplitude modulation at the frequency of the rf drive applied to the fiber-coupled electro-optic modulator is reduced to less than 1 × 10-6 fractional amplitude modulation at τ > 1 s by an active servo. The contribution of residual amplitude modulation to the laser-frequency instability is further reduced by digital division of the transmission and incident photodetector signals to less than 1 × 10-16 at τ > 1 s. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance (NMR) and transport measurements have been performed at high magnetic fields and low temperatures in a series of n-type Bi2Se3 crystals. In low-density samples, a complete spin polarization of the electronic system is achieved, as observed from the saturation of the isotropic component of the 209Bi NMR shift above a certain magnetic field. The corresponding spin splitting, defined in the phenomenological approach of a 3D electron gas with a large (spin-orbit-induced) effective g factor, scales as expected with the Fermi energy independently determined by simultaneous transport measurements. Both the effective electronic g factor and the "contact" hyperfine coupling constant are precisely determined. The magnitude of this latter reveals a nonnegligible r character of the electronic wave function at the bottom of the conduction band. Our results show that the bulk electronic spin polarization can be directly probed via NMR and pave the way for future NMR investigations of the electronic states in Bi-based topological insulators. [ABSTRACT FROM AUTHOR]

We have studied EuPtP, which undergoes two successive valence transitions at TA~240 K and TB~200 K by 31P-nuclear magnetic resonance (NMR) measurements. From the analysis of NMR spectra, we obtained plausible ordered structures and Eu valence states in three phases divided by TA and TB. These ordered structures well explain observed inequivalent P sites and the intensity ratio of the NMR spectra arising from these P sites. The results are also in good accordance with mean Eu valence measured by the x-ray absorption spectroscopy. We also discuss Eu 4f states and the origin of the transitions from the measurements of nuclear spin lattice relaxation rate and hyperfine coupling constant. [ABSTRACT FROM AUTHOR]

The organic conductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl has been studied for the examination of the conducting mechanism of the semiconducting behavior at high temperatures by 13C-NMR spectroscopy. We found that the temperature dependence of the linewidths and the spin-spin relaxation rate T2-1 showed a peak structure characterized by the hyperfine coupling constant in this region, suggesting a connection between ethylene motion and conducting electrons similar to that observed in κ-(BEDT-TTF)2Cu(NCS)2. Although all κ-(BEDT-TTF)2Cu[N(CN)2]Cl salt was thought to be an insulator at high temperature, our findings suggest that all κ-type salts at high temperatures could be in the same phase where the scattering caused by ethylene motion is added to bad metal. [ABSTRACT FROM AUTHOR]

Complex ac susceptibility, χ = χ' - iχ", measurements of the clathrate compound Pr3Pd20Ge6 were performed in static fields up to 10 mT for H ‖ [001] and at temperatures down to 500 μK. Praseodymium (Pr) nuclear magnetic moments at the 8c site, where quadrupole moments of 4 f electrons order at TQ1 = 250 mK, were found to order antiferromagnetically at 9 mK, as shown by a peak in χ' and a substantial increase in thermal relaxation time. The large enhancement factor (1 + K8c) obtained by calculation of the hyperfine-enhanced nuclear susceptibility of Pr at the 8c site accounts for the high transition temperature of Pr nuclear magnetic moments and the large χ' below 30 mK. From analysis of the crystalline electric field and the mean-field approximation, we conclude that a χ peak at 77 mK can be ascribed to an antiferromagnetic ordering of magnetic moments of 4 f electrons at the 4a site. We found that nuclear and f-electron moments order separately on two sublattices in this compound. The temperature and magnetic field dependence of χ' and χ" between 30 and 60 mK are discussed in terms of dissipation phenomena. [ABSTRACT FROM AUTHOR]

Quantum memories are integral parts of both quantum computers and quantum communication networks. Naturally, such a memory is embedded into a hybrid quantum architecture, which has to meet the requirements of fast gates, long coherence times, and long distance communication. Erbium-doped crystals are well suited as a microwave quantum memory for superconducting circuits with additional access to the optical telecom C band around 1.55 μm. Here, we report on circuit QED experiments with an Er3+:YAlO3 crystal and demonstrate strong coupling to a superconducting lumped element resonator. The low magnetic anisotropy of the host crystal allows for attaining the strong coupling regime at relatively low magnetic fields, which are compatible with superconducting circuits. In addition, Ce3+ impurities were detected in the crystal, which showed strong coupling as well. [ABSTRACT FROM AUTHOR]

High-resolution spectroscopy of the 2s1/2−2p1/2 transition in the extreme ultraviolet region is shown to resolve the level splitting induced by the nuclear magnetic field of both the 2s1/2 and the 2p1/2 levels in lithiumlike 141Pr56+ and of the 2s1/22p1/2 3P1 level in berylliumlike 141Pr56+. The 141Pr ions are an ideal test of this measurement approach because their energy levels are known well from first principles and are unaffected by small energy contributions from QED and nuclear magnetization effects. The accuracy attained in the measured 196.5±1.2 meV 2s1/2 splitting is more than an order of magnitude better than that achieved before using crystal spectroscopy of the 2s1/2−2p3/2 x-ray transition and at the level needed to implement a proposed scheme for disentangling the contributions from QED and nuclear magnetization effects in higher-Z ions, such as 209Bi. [ABSTRACT FROM AUTHOR]

We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically defined double quantum dot in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections. [ABSTRACT FROM AUTHOR]

Bismuth donors ion-implanted in 28Si and natSi are studied using magnetic resonance spectroscopy based on spin-dependent recombination. The hyperfine clock transition, at which the linewidth is significantly narrowed, is observed for the bismuth donors. The experimental results are modeled quantitatively by molecular orbital theory for a coupled pair consisting of a bismuth donor and a spin-dependent recombination readout center, including the effect of hyperfine and Zeeman interactions. [ABSTRACT FROM AUTHOR]

We present the complete result for the O(α7me) one photon annihilation contribution to the hyperfine splitting of the ground state energy levels in positronium. Numerically it increases the prediction of quantum electrodynamics by 217 ± 1 kHz. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) is used to investigate the triplet (S = 1) ground state of the neutral oxygen vacancy in bulk rutile TiO2 crystals. This shallow donor consists of an oxygen vacancy with two nearest-neighbor, exchange-coupled Ti3+ ions located along the [001] direction and equidistant from the vacancy. The spins of the two trapped electrons, one at each Ti3+ ion, align parallel to give the S = 1 state. These neutral oxygen vacancies are formed near 25 K in as-grown oxidized TiO2 crystals by illuminating with sub-band-gap 442 nm laser light. The angular dependence of the EPR spectra provides the principal values and axes for the g and D matrices. Observations of the Ti and Ti hyperfine lines when the magnetic field is along high-symmetry directions show that the two Ti3+ ions are equivalent; i.e., they have equal hyperfine A matrices. The A matrix for each Ti3+ ion in the neutral S = 1 oxygen vacancy is approximately half of the A matrix reported earlier for the one Ti3+ ion in the singly ionized S = 1/2 oxygen vacancy [Brant et al., J. Appl. Phys. 114, 113702 (2013)]. The neutral oxygen vacancies are thermally unstable above 25 K. They release an electron to the conduction band with an activation energy near 63 meV and convert to singly ionized S = 1/2 oxygen vacancies. When undoped TiO2 is sufficiently oxygen deficient (i.e., reduced), this combination of conduction band electrons and singly ionized oxygen vacancies may result in carrier-mediated ferromagnetism at room temperature. [ABSTRACT FROM AUTHOR]

We consider the production of dynamic nuclear spin polarization (DNP) in a two-electron double quantum dot, in which the electronic levels are repeatedly swept through a singlet-triplet avoided crossing. Our analysis helps to elucidate the intriguing interplay between electron-nuclear hyperfine coupling, electronic spin-orbit coupling, and electron and nuclear Larmor precession in an externally applied magnetic field in guiding the production of DNP In particular, we specifically address the roles of multiple nuclear spin species. By treating the nuclear spin dynamics semiclassically, we identify two contributions to the DNP production rate, a "geometric contribution" and a "dynamic contribution," which depend in very different ways on control parameters such as the sweep rate and holding time near the level crossing, We find that the dynamical contribution dominates the DNP when the system is held near the singlet-triplet, avoided crossing for a time on the order of the nuclear Larmor period. Detailed numerical calculations provide a physical picture for understanding the oscillations observed by Foletti et al. in arXiv:0801.3613. [ABSTRACT FROM AUTHOR]

We present composite pulse sequences that perform fault-tolerant two-qubit gate operations on exchange-only quantum-dot spin qubits in various experimentally relevant geometries. We show how to perform dynamically corrected two-qubit gates in exchange-only systems with the leading hyperfine error term canceled. These pulse sequences are constructed to conform to the realistic experimental constraint of strictly non-negative couplings. We establish that our proposed pulse sequences lead to several orders of magnitude improvement in the gate fidelity compared with their uncorrected counterparts. Together with single-qubit dynamically corrected gates, our results enable noise-resistant universal quantum operations with exchange-only qubits. [ABSTRACT FROM AUTHOR]

The frequency splitting between the dip and the peak of the resistively detected nuclear magnetic resonance dispersive line shape has been measured in the quantum Hall effect regime as a function of filling factor, carrier density, and nuclear isotope. The splitting increases as the filling factor tends to v = 1 and is proportional to the hyperfine coupling, similar to the usual Knight shift versus v dependence. The peak frequency shifts linearly with magnetic field throughout the studied filling factor range and matches the unshifted substrate signal, detected by classical NMR. Thus, the evolution of the splitting is entirely due to the changing Knight shift of the dip feature. The nuclear spin relaxation time T1 is extremely long (∼hours) at precisely the peak frequency. These results are consistent with the local formation of a v = 2 phase due to the existence of spin singlet D- complexes. [ABSTRACT FROM AUTHOR]

Magnetic and elastic properties of Ni metal have been studied up to 260 GPa by nuclear forward scattering of synchrotron radiation with the 67.4 keV Mossbauer transition of 61 Ni. The observed magnetic hyperfine splitting confirms the ferromagnetic state of Ni up to 260 GPa, the highest pressure where magnetism in any material has been observed so far. Ab initio calculations reveal that the pressure evolution of the hyperfine field, which features a maximum in the range of 100 to 225 GPa, is a relativistic effect. The Debye energy obtained from the Lamb-Mossbauer factor increases from 33 me Vat ambient pressure to 60 me Vat 100 GPa. The change of this energy over volume compression is well described by a Grüneisen parameter of 2.09. [ABSTRACT FROM AUTHOR]

The authors focus on study of elastic and magnetic properties of Nickel metal. The authors mention that, with use of nuclear forward scattering of synchrotron radiation and under pressure up to 260 gigapascal, the Mossbauer transaction of nickel was observed. The authors report that the magnetic hyperfine splitting showed that Nickel is a ferromagnetic at such high pressure, making it a first instance of any material displaying magnetism at such pressures.

Migratory birds can utilize the geomagnetic field for orientation and navigation through a widely accepted radical-pair mechanism. Although many theoretical works have been done, the available experimental results have not been fully considered, especially the temporary disorientation induced by the field which is increased by 30% of the geomagnetic field and the disorientation of the very weak resonant field of 15 nT. In this paper, we consider the monotonicity of the singlet yield angular profile as the prerequisite of direction sensitivity, and find that for some optimal values of the hyperfine coupling parameters (that is, the order of 10-7 ~ 10-6 meV) the experimental results available so far can be satisfied. We also investigate the effects of two decoherence environments and demonstrate that, in order to satisfy the available experimental results, the decoherence rate should be lower than the recombination rate. Finally, we investigate the effects of the fluctuating magnetic noises and find that the vertical noise destroys the monotonicity of the profile completely, but the parallel noise preserves the monotonicity perfectly and even can enhance the direction sensitivity. [ABSTRACT FROM AUTHOR]

We demonstrate bias control of the efficiency of the hyperfine coupling between a single electron in an InAs quantum dot and the surrounding nuclear spins monitored through the positively charged exciton X+ emission. In applied longitudinal magnetic fields, we vary simultaneously the correlation time of the hyperfine interaction and the nuclear spin relaxation time and thereby the amplitude of the achieved dynamic nuclear polarization under optical pumping conditions. In applied transverse magnetic fields, a change in the applied bias allows a switch from the anomalous Hanle effect to the standard electron spin depolarization curves. [ABSTRACT FROM AUTHOR]

We demonstrate that the volume of the Fermi surface, measured very precisely using de Haas-van Alphen oscillations, can be used to probe changes in the nature and occupancy of localized electronic states. In systems with unconventional ordered states, this allows an underlying electronic order parameter to be followed to very low temperatures. We describe this effect in the field-induced antiferroquadrupolar (AFQ) ordered phase of PrOs4Sb12, a heavy fermion intermetallic compound. We find that the phase of de Haas-van Alphen oscillations is sensitively coupled, through the Fermi volume, to the configuration of the Pr f-electron states that are responsible for AFQ order. In particular, the β sheet of the Fermi surface expands or shrinks as the occupancy of two competing localized Pr crystal field states changes. Our results are in good agreement with previous measurements, above 300 mK, of the AFQ order parameter by other methods. In addition, the low-temperature sensitivity of our measurement technique reveals a strong and previously unrecognized influence of hyperfine coupling on the order parameter below 300 mK within the AFQ phase. Such hyperfine couplings could provide insight into the nature of hidden order states in other systems. [ABSTRACT FROM AUTHOR]

We study the ternary clathrate Pr3Pd20Si6 in specific heat and ac susceptibility measurements on a high-quality single crystal, distinguishing antiferromagnetic and antiferroquadnipolar ordering, as well as a hitherto unknown magnetic low-temperature transition. The specific heat shows the direct involvement of nuclear spin degrees of freedom in the antiferromagnetic ordering, which is well supported by our calculation of the hyperfine level scheme without adjustable parameters. Pr3Pd20Si6 is, therefore, one of the rare materials where the nuclear moments are involved in the formation of the magnetic ground state. [ABSTRACT FROM AUTHOR]

We provide ab initio characterization of the negatively charged substitutional nickel (Ni-s) impurity in diamond using a hybrid density functional calculation. Ni; is shown to carry a spin S = 3/2. The calculated hyperfine couplings on this defect support the identification of the W8 electron paramagnetic resonance center with Ni-s defect. We unambiguously determine the position of the Ni-s acceptor level in the gap. This level is located at about 2.0 eV above the valence band maximum and corresponds to a totally occupied triplet state responsible for the magnetization. We calculated the excited state properties of the defect. Our results may resolve the controversial assignments of Ni-s to different optical centers. [ABSTRACT FROM AUTHOR]

We present a combined analysis of the electromagnetic form factors of the nucleon in the space- and timelike regions using dispersion theory. Our framework provides a consistent description of the experimental data over the full range of momentum transfer, in line with the strictures from analyticity and unitarity. The statistical uncertainties of the extracted form factors are estimated using the bootstrap method, while systematic errors are determined from variations of the spectral functions. We also perform a high-precision extraction of the nucleon radii and find good agreement with previous analyses of spacelike data alone. For the proton charge radius, we find rpE=0.840+0.003-0.002+0.002-0.002 fm, where the first error is statistical and the second one is systematic. The Zemach radius and third moment are in agreement with Lamb shift measurements and hyperfine splittings. The combined dataset of space- and timelike data disfavors a zero crossing of μpGpE/GpM in the spacelike region. Finally, we discuss the status and perspectives of modulus and phase of the form factors in the timelike region in the context of future experiments, as well as the onset of perturbative QCD. [ABSTRACT FROM AUTHOR]

We show that muonium spectroscopy in the coming years can reach a precision high enough to determine the anomalous magnetic moment of the muon below one part per million (ppm). Such an independent determination of muon g-2 would certainly shed light on the ∼2  ppm difference currently observed between spin-precession measurements and (R-ratio based) standard model predictions. The magnetic dipole interaction between electrons and (anti)muons bound in muonium gives rise to a hyperfine splitting (HFS) of the ground state which is sensitive to the muon anomalous magnetic moment. A direct comparison of the muonium frequency measurements of the HFS at J-PARC and the 1S-2S transition at PSI with theory predictions will allow us to extract muon g-2 with high precision. Improving the accuracy of QED calculations of these transitions by about 1 order of magnitude is also required. Moreover, the good agreement between theory and experiment for the electron g-2 indicates that new physics interactions are unlikely to affect muonium spectroscopy down to the envisaged precision. [ABSTRACT FROM AUTHOR]

The world data on elastic electron scattering on ³He and 4He is used to determine the Zemach moments (r)(2) and (r³)(2). These quantities are required to interpret the Lamb shift and hyperfine splitting data of muonic helium presently being measured at the Paul Scherrer Institute by the CREMA Collaboration. The rms radii are determined as well. [ABSTRACT FROM AUTHOR]

Three-loop corrections to hyperfine splitting in muonium, generated by the gauge-invariant sets of diagrams with muon and tauon loop light-by-light scattering blocks, are calculated. These results complete calculations of all light-by-light scattering contributions to hyperfine splitting in muonium. [ABSTRACT FROM AUTHOR]

The article presents information on a study which focuses on the calculation of the muon and tauon light-by-light (LBL) scattering contributions to hyperfine splitting (HFS) in muonium. It focuses on three-loop corrections to hyperfine splitting in muonium, generated by the electron LBL scattering block.