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The authors define a Banach space $\\mathcal{M}_{1}$ of models for fermions or quantum spins in the lattice with long range interactions and make explicit the structure of (generalised) equilibrium states for any $\\mathfrak{m}\\in \\mathcal{M}_{1}$. In particular, the authors give a first answer to an old open problem in mathematical physics--first addressed by Ginibre in 1968 within a different context - about the validity of the so-called Bogoliubov approximation on the level of states. Depending on the model $\\mathfrak{m}\\in \\mathcal{M}_{1}$, the authors' method provides a systematic way to study all its correlation functions at equilibrium and can thus be used to analyse the physics of long range interactions. Furthermore, the authors show that the thermodynamics of long range models $\\mathfrak{m}\\in \\mathcal{M}_{1}$ is governed by the non-cooperative equilibria of a zero-sum game, called here thermodynamic game.

There are numerous recent and ongoing experiments employing a variety of atomic species to search for couplings of atomic spins to exotic fields. In order to meaningfully compare these experimental results, the coupling of the exotic field to the atomic spin must be interpreted in terms of the coupling to electron, proton, and neutron spins. Traditionally, constraints from atomic experiments on exotic couplings to neutron and proton spins have been derived using the single-particle Schmidt model for nuclear spin. In this model, particular atomic species are sensitive to either neutron or proton spin couplings, but not both. More recently, semi-empirical models employing nuclear magnetic moment data have been used to derive new constraints for non-valence nucleons. However, comparison of such semi-empirical models to detailed large-scale nuclear shell model calculations and analysis of known physical effects in nuclei show that existing semi-empirical models cannot reliably be used to predict the spin polarization of non-valence nucleons. The results of our re-analysis of nuclear spin content are applied to searches for exotic long-range monopole-dipole and dipole-dipole couplings of nuclei leading to significant revisions of some published constraints.

Color centers in solids, such as the nitrogen-vacancy center in diamond, offer well-protected and well-controlled localized electron spins that can be employed in various quantum technologies. Moreover, the long coherence time of the surrounding spinful nuclei can enable a robust quantum register controlled through the color center. We design pulse sequence protocols that drive the electron spin to generate robust entangling gates with these nuclear memory qubits. We find that compared to using Carr-Purcell-Meiboom-Gill (CPMG) alone, Uhrig decoupling sequence and hybrid protocols composed of CPMG and Uhrig sequences improve these entangling gates in terms of fidelity, spin control range, and spin selectivity. We provide analytical expressions for the sequence protocols and also show numerically the efficacy of our method on nitrogen-vacancy centers in diamond. Our results are broadly applicable to color centers weakly coupled to a small number of nuclear spin qubits.

We propose a correction to the coefficient of nuclear spin diffusion by a factor 1 / 1 − p ̄ 2 , where p ̄ is the average nuclear spin polarization. The correction, derived by extending the Lowe–Gade theory to low-temperature cases, implies that transportation of nuclear magnetization through nuclear spin diffusion accelerates when the system is hyperpolarized, whereas for low polarization the correction factor approaches unity and the diffusion coefficient coincides with the conventional diffusion coefficient valid in the high-temperature limit. The proposed scaling of the nuclear spin diffusion coefficient can lead to observable effects in the buildup of nuclear polarization by dynamic nuclear polarization.

The search for long-lived quantum memories, which can be efficiently interfaced with flying qubits, is longstanding. One possible solution is to use the electron spin of a color center in diamond to mediate interaction between a long-lived nuclear spin and a photon. Realizing this in a nanodiamond furthermore facilitates the integration into photonic devices and enables the realization of hybrid quantum systems with access to quantum memories. Here, we investigated the spin environment of negatively charged silicon-vacancy centers in a nanodiamond and demonstrate strong coupling of its electron spin, while the electron spin’s decoherence rate remained below 1 MHz. We furthermore demonstrate multi-spin coupling with the potential to establish registers of quantum memories in nanodiamonds.

Magnetic resonance techniques are powerful, nondestructive, non-invasive tools with broad applications in radiation dosimetry. Electron paramagnetic resonance (EPR) enables direct quantification of dose-dependent radiation-induced paramagnetic defects, while nuclear magnetic resonance (NMR) reflects the influence of such defects through changes in line width and nuclear spin relaxation. To date, these methods have typically been applied independently. Their combined use to probe radiation damage in the same material offers new opportunities for comprehensive characterization and preferred dosimetry techniques. In this work, we apply both EPR and NMR to investigate radiation damage in lithium carbonate (Li2CO3). A detailed EPR analysis of γ-irradiated samples shows that the concentration of paramagnetic defects increases with dose, following two distinct linear regimes: 10–100 Gy and 100–1000 Gy. A gradual decay of the EPR signal was observed over 40 days, even under cold storage. In contrast, 7Li NMR spectra and spin–lattice relaxation times in Li2CO3 exhibit negligible sensitivity to radiation doses up to 1000 Gy, while 1H NMR results remain inconclusive. Possible mechanisms underlying these contrasting behaviors are discussed.

Surface nuclear magnetic resonance (SNMR) is a newly developed, non-invasive geophysical method designed for groundwater prospecting. This book provides an overview of the SNMR method and a cost-benefit analysis of SNMR against other geophysical methods applied to groundwater study. It assesses the methodology of field measurements and gives examples of real data interpretation, and deals with some of the most pervasive problems faced by the SNMR methodology. Based on the author's extensive teaching experience, this book is designed to acquaint a wide but specialist audience of researchers and professionals in hydrogeology and geophysics with the SNMR method.

Spin-based quantum information processing makes extensive use of spin-state manipulation. This ranges from dynamical decoupling of nuclear spins in quantum sensing experiments to applying logical gates on qubits in a quantum processor. Fast manipulation of spin states is highly desirable for accelerating experiments, enhancing sensitivity, and applying elaborate pulse sequences. Strong driving using intense radio-frequency (RF) fields can, therefore, facilitate fast manipulation and enable broadband excitation of spin species. In this work, we present an antenna for strong driving in quantum sensing experiments and theoretically address challenges of the strong driving regime. First, we designed and implemented a micron-scale planar spiral RF antenna capable of delivering intense fields to a sample. The planar antenna is tailored for quantum sensing experiments using the diamond’s nitrogen-vacancy (NV) center and should be applicable to other solid-state defects. The antenna has a broad bandwidth of 22 MHz, is compatible with scanning probes, and is suitable for cryogenic and ultrahigh vacuum conditions. We measure the magnetic field induced by the antenna and estimate a field-to-current ratio of 113 ± 16  G/A, representing a six-fold increase in efficiency compared to the state-of-the-art, crucial for cryogenic experiments. We demonstrate the antenna by driving Rabi oscillations in 1 H spins of an organic sample on the diamond surface and measure 1 H Rabi frequencies of over 500 kHz, i.e. π -pulses shorter than 1  μ s —an order of magnitude faster than previously reported in NV-based nuclear magnetic resonance (NMR). Finally, we discuss the implications of driving spins with a field tilted from the transverse plane in a regime where the driving amplitude is comparable to the spin-state splitting, such that the rotating wave approximation does not describe the dynamics well. We present a simple recipe to optimize pulse fidelity in this regime based on a phase and offset-shifted sine drive, which may be optimized in situ without numerical optimization procedures or precise modeling of the experiment. We consider this approach in a range of driving amplitudes and show that it is particularly efficient in the case of a tilted driving field. The results presented here constitute a foundation for implementing fast nuclear spin control in various systems.

The nuclear spin-lattice relaxation time T 1 of the ν  = 2 quantum Hall ferromagnet (QHF) formed in a gate-controlled InSb two-dimensional electron gas has been characterized using a pump-probe technique. In contrast to a long T 1 of quantum Hall states around ν  = 1 that possesses a Korringa-type temperature dependence, the temperature-independent short T 1 of the ν  = 2 QHF suggests the presence of low energy collective spin excitations in a domain wall. Furthermore, T 1 of this ferromagnetic state is also found to be filling- and current-independent. The interpretation of these results as compared to the T 1 properties of other QHFs is discussed in terms of the domain wall skyrmion, which will lead to a better understanding of the QHF.

The rate of nuclear spin-lattice relaxation is determined by the efficiency of interaction between thermal phonons and nuclear spins. The results on reducing the efficiency of spin–phonon coupling by suppressing the contribution from paramagnetic centers to quadrupole nucleus relaxation are presented. The suppression has been performed by continuous magnetic action at the Larmor frequency. It is shown that, as in the presence of an acoustic field, the rate of spin-lattice relaxation of 23 Na nuclei in a sodium fluoride crystal at magnetic saturation of the NMR signal does not change in the region of a negative average spin temperature. In the region of positive spin temperature, the rate of relaxation of 23 Na spins significantly decreases and nuclear magnetization recovery with time is described by the sum of two exponentials. The contribution from nuclear spins with a lower efficiency of spin–phonon coupling, corresponding to the exponential with a long relaxation time, increases with increasing saturating field intensity. It is demonstrated that the efficiency of spin–phonon coupling for 19 F nuclei, which do not have the quadrupole moment, does not change under the saturation conditions. The results obtained can be used for analyzing the structure of real crystals.