Nuclear Magnetic Spin Research Articles

Accelerated 2D Cartesian MRI with an 8-channel local B0 coil array combined with parallel imaging.

In MRI, the magnetization of nuclear spins is spatially encoded with linear gradients and radiofrequency receiverssensitivity profiles to produce images, which inherently leads to a long scan time. Cartesian MRI, as widely adopted for clinical scans, can be accelerated with parallel imaging and rapid magnetic field modulation during signal readout. Here, by using an 8-channel local coil array, the modulation scheme optimized for sampling efficiency is investigated to speed up 2D Cartesian scans. An 8-channel local coil array is made to carry sinusoidal currents during signal readout to accelerate 2D Cartesian scans. An MRI sampling theory based on reproducing kernel Hilbert space is exploited to visualize the efficiency of nonlinear encoding in arbitrary sampling duration. A field calibration method using current monitors for local coils and the ESPIRiT algorithm is proposed to facilitate image reconstruction. Image acceleration with various modulation field shapes, aliasing control, and distinct modulation frequencies are scrutinized to find an optimized modulation scheme. A safety evaluation is conducted. In vivo 2D Cartesian scans are accelerated by the local coils. For 2D Cartesian MRI, the optimal modulation field by this local array converges to a nearly linear gradient field. With the field calibration technique, it accelerates the in vivo scans (i.e., proved safe) by threefold and eightfold free of visible artifacts, without and with SENSE, respectively. The nonlinear encoding analysis tool, the field calibration method, the safety evaluation procedures, and the in vivo reconstructed scans make significant steps to push MRI speed further with the local coil array.

Nuclear spin effects in biological processes

Traditionally, nuclear spin is not considered to affect biological processes. Recently, this has changed as isotopic fractionation that deviates from classical mass dependence was reported both in vitro and in vivo. In these cases, the isotopic effect correlates with the nuclear magnetic spin. Here, we show nuclear spin effects using stable oxygen isotopes (16O, 17O, and 18O) in two separate setups: an artificial dioxygen production system and biological aquaporin channels in cells. We observe that oxygen dynamics in chiral environments (in particular its transport) depend on nuclear spin, suggesting future applications for controlled isotope separation to be used, for instance, in NMR. To demonstrate the mechanism behind our findings, we formulate theoretical models based on a nuclear-spin-enhanced switch between electronic spin states. Accounting for the role of nuclear spin in biology can provide insights into the role of quantum effects in living systems and help inspire the development of future biotechnology solutions.

Paramagnetic relaxivity of delocalized long-lived states of protons in chains of CH2 groups.

Long-lived states (LLSs) have lifetimes that can be much longer than longitudinal relaxation times . In molecules containing several geminal pairs of protons in neighboring CH groups, it has been shown that delocalized LLSs can be excited by converting magnetization into imbalances between the populations of singlet and triplet states of each pair. Since the empirical yield of the conversion and reconversion of observable magnetization into LLSs and back is on the order of 10 % if one uses spin-lock induced crossing (SLIC), it would be desirable to boost the sensitivity by dissolution dynamic nuclear polarization (d-DNP). To enhance the magnetization of nuclear spins by d-DNP, the analytes must be mixed with radicals such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL). After dissolution, these radicals lead to an undesirable paramagnetic relaxation enhancement (PRE) which shortens not only the longitudinal relaxation times but also the lifetimes of LLSs. It is shown in this work that PRE by TEMPOL is less deleterious for LLSs than for longitudinal magnetization for four different molecules: 2,2-dimethyl-2-silapentane-5-sulfonate (DSS), homotaurine, taurine, and acetylcholine. The relaxivities (i.e., the slopes of the relaxation rate constants as a function of the radical concentration) are 3 to 5 times smaller than the relaxivities of longitudinal magnetization. Partial delocalization of the LLSs across neighboring CH groups may decrease this advantage, but in practice, this effect was observed to be small, for example, when comparing taurine containing two CH groups and homotaurine with three CH groups. Regardless of whether the LLSs are delocalized or not, it is shown that PRE should not be a major problem for experiments combining d-DNP and LLSs, provided the concentration of paramagnetic species after dissolution does not exceed 1 mM, a condition that is readily fulfilled in typical d-DNP experiments. In bullet d-DNP experiments however, it may be necessary to decrease the concentration of TEMPOL or to add ascorbate for chemical reduction.

How to Use Nested Probes Coupling to Increase the Local NMR/MRI Resolution and Sensitivity for Specific Experiments

In this paper, we address resonant systems intended to be used with the commercial main resonator present on all NMR or MRI instruments. The purpose of this approach is to get an improvement regarding the spatial localization and signal to noise ratio provided by an additional smaller coil. Both coils are coupled to the same sample region, and thus, are inductively coupled through their common magnetic flux. The coupling strength is characterized by the so-called mutual inductance M. Two practical devices are presented. Firstly, a geometrical passive decoupled resonant system (M = 0) allows getting a sensitive received signal from the maximized nuclear macroscopic magnetization, excited by the main resonator and detected by the smaller sniffer coil. Secondly, a strongly coupled resonant system allows us to considerably locally improve the magnetic component of the RF near field to provide an efficient nuclear spin magnetization excitation and a high received signal. For both configurations, the behavior of the coils system regarding the amplitude of B1 is addressed. Finally, specific technical hints to achieve optimum energy transfer (impedance matching) are discussed, taking into account the non-ideal RF characteristics of the involved components. Examples of MRI experiments, as well as workbench evaluations and simulations support the principles exposed here.

Site-based description of R1ρ relaxation in local reference frames

Nuclear magnetic spin relaxation in the presence of an applied radiofrequency field depends critically on chemical exchange processes that transfer nuclear spins between chemical or conformational environments with distinct resonance frequencies. Characterization of chemical exchange processes in R1ρ relaxation dispersion, CEST, and DEST experiments provides powerful insights into chemical and conformational kinetics of biological macromolecules. The present work reformulates expressions for magnetization evolution and the R1ρ relaxation rate constant by focussing on the orientations of the tilted rotating frames of reference for magnetization components in different sites, by treating the spin-locking field strength as a perturbation to free-precession evolution, and by applying the Homotopy Analysis and Laplace transform methods to approximate solutions to the Bloch-McConnell equations. The results provide an expression for R1ρ that is invariant to the topology of the kinetic scheme, an approximate equation for evolution of spin-locked z-magnetization, and an approach for effective simplification of chemical exchange topologies for 2- and N-site chemical exchange processes. The theoretical approach also provides an accurate approximation for relaxation during a constant-amplitude radiofrequency field in the absence of exchange.

NMR Relaxometry Using Outer Field of Single-Sided HTS Bulk Magnet Activated by Pulsed Field

We have succeeded in getting <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> H NMR signals at 47.8 MHz (1.12 T) from a single-sided HTS bulk magnet activated by pulse-field magnetization. Diffusion NMR using an inhomogeneous outer field was also demonstrated on the surface. This kind of NMR relaxometry can not get the information of molecular structures, which conventional NMR using a homogeneous magnetic field can acquire. However, the relaxation of nuclear spin magnetization is still observable. A higher magnetic field gradient generated by the small HTS bulk magnet, 67 T/m at a 5 mm distance from the surface, can be effectively used to observe the self-diffusion coefficient of liquids in higher spatial resolution, 44 μm. The easy accessibility to the strong field gradient is one of the unique properties ofcompact HTS bulk magnets. We believe that single-sided (unilateral) diffusion NMR will become the new application of HTS bulk magnets.

Response dynamics of an alkali-metal–noble-gas hybrid trispin system

With numerical calculation of coupled Bloch equations, we have simulated the spin dynamics of nuclear magnetic resonance gyroscope based on alkali metal-noble gas hybrid trispin system. From the perspective of damping harmonic oscillator, a thorough analysis of the response dynamics is demonstrated. The simulation results shows a linear increasing response of gyroscope signal while the noblge gas nuclear spin magnetization and alkali atomic spin lifetime parameters are at the over damping condition. An upper limit of response is imposed on the NMR gyroscope signal due to the inherent dynamics of the hybrid trispin system. The results agrees with present available experimental results and provide useful guidings for future experiments.

(Invited) Isotopically Engineered Silicon Testbeds for Advanced CMOS and Quantum Information

Silicon isotope engineering invokes a new paradigm into materials science for development of advanced CMOS technology and practical quantum computers [1]. Current development of planer-type CMOS devices confronts an immediate issue for downscaling limit, demanding a basal changeover to gate-all-around transistors employing three-dimensional (3D) nanostructures, such as vertical nanowires or stacked nanosheets. Recently, nanoscale metrology of 3D electronic devices is enabled by means of atom probe tomography (APT) having nearly atomic resolution [2]. We extended this APT technique to verify Si self-diffusion in isotopically modulated nanopillars, which allowed spatial visualization of individual isotope atoms crossing the heterointerface [3]. As a result, Si self-diffusivity in gate-oxidized nanopillars having a diameter of ~200 nm was found to remain the same as the one measured for standard planar oxidation. More recently, process tracking technique based on transmission electron microscope (TEM) was established for identical Si nanopillars, which led to unveil a gate-oxidation overview for various conditions [4]. In addition, the silicon isotope engineering provides a crucial solution to eliminate unwanted decoherence for Si-based spin qubits. We adopted the isotope engineering to tailor high-quality CVD-grown 28Si epi-wafers [1], where state-of-the-art Si-MOS nanoelectronic devices were implemented to demonstrate two-qubits operations encoded by single donor electron and nuclear spins [5]. In parallel, the isotopically enriched wafers were employed to demonstrate single and two spin-qubit operations in 28Si-MOS quantum dots (QDs) that were defined by standard CMOS lithography [6]. Meanwhile, we accomplished isotope enrichment of strained-Si/SiGe quantum-well (QW) heterostructures, where the QDs were placed away from gate-oxide interface traps. Thanks to efficient suppression of magnetic nuclear-spin noise, the isotopically enriched 28Si/SiGe QDs prolonged electron-spin dephasing time, consequently recording the highest single-spin gate fidelities of 99.93% in benchmark test [7]. However, it was revealed that inherent charge noise induces temporal fluctuation of qubit frequency. Moreover, the low-energy excited states responsible for Si valley degeneracy should be well-lifted for the higher-fidelity operations, including spin-qubit readout and initialization. Our recent 28Si/SiGe heterostructures exhibit large valley splitting, demonstrating a well-defined QW interface having fewer atomic-scale steps [8]. And also, major impurities of carbon and oxygen can be suppressed below 1016 cm-3. In order to address the remaining source of step generation, we developed direct imaging scheme for crystallographic tilting effects on the basis of the TEM diffraction [9]. It has been identified that the local lattice rotation is preferentially caused in the proximity of the dislocations having threading components. This fact provides experimental signature for the global step generation at the QW interface.This work has been supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118069228, JST-ACCEL Grant Number JPMJAC1301, and the Center for Spintronics Research Network, Keio University. The authors acknowledge fruitful collaborations with Yasuyoshi Nagai, Yasuo Shimizu, Tetsuo Endoh, Seigo Tarucha, Mark Eriksson, Andrew Dzurak and Andrea Morello.[1] K. M. Itoh and H. Watanabe, MRS Communications 4, 143 (2014).[2] D. J. Larson et al., MRS Bulletin 41, 30 (2016).[3] R. Kiga et al., J. Appl. Phys. 127, 045704 (2020).[4] T. Wako et al., in preparation.[5] J.T. Mohonen et al., Nature Nanotechnol. 9, 986 (2014).[6] M. Veldhorst et al., Nature Nanotechnol. 9, 981 (2014); M. Veldhorst et al., Nature 526, 410 (2015).[7] J. Yoneda et al., Nature Nanotechnol. 13, 102 (2018).[8] S. Miyamoto et al., IEEE IEDM – Technical Digest, pp.6.4.1 - 6.4.4 (2018).[9] K. Takeuchi et al., in preparation.

Approximate Representations of Shaped Pulses Using the Homotopy Analysis Method.

The evolution of nuclear spin magnetization during a radiofrequency pulse in the absence of relaxation or coupling interactions can be described by three Euler angles. The Euler angles in turn can be obtained from the solution of a Riccati differential equation; however, analytic solutions exist only for rectangular and chirp pulses. The Homotopy Analysis Method is used to obtain new approximate solutions to the Riccati equation for shaped radiofrequency pulses in NMR spectroscopy. The results of even relatively low orders of approximation are highly accurate and can be calculated very efficiently. The results are extended in a second application of the Homotopy Analysis Method to represent relaxation as a perturbation of the magnetization trajectory calculated in the absence of relaxation. The Homotopy Analysis Method is powerful and flexible and is likely to have other applications in magnetic resonance.

Study on hemodynamics of high altitude polycythemia by 3D-ASL combined with CT cerebral perfusion

Objective To investigate the changes of CT cerebral perfusion (CTP) and the application value of nuclear magnetic resonance proton spin labeling (3D-ASL) and to conduct a comparative study. Methods Multi-slice spiral CT(MDCT) was used to study the changes of CTP in 22 patients with HAPC. Comparison of CT whole-brain perfusion technique and nuclear magnetic resonance proton spin labeling technique (3D-ASL) in hemodynamic changes of the brain in plateau polycythemia. Results With the aggravation of HAPC, CBF of cerebral cortex and white matter showed a downward trend. Except the white matter of frontal lobe and temporal lobe, the difference of HAPC among different diseases was statistically significant ( P < 0.05). Along with the aggravation of, each part of the brain cortex and white matter CBV increase, white matter, and each part CBV difference had statistical significance between different condition ( P < 0.05). With the aggravation of the disease, the MTT of cortex and white matter in all parts of the brain increased significantly, and the difference of MTT between different parts of the disease was statistically significant ( P < 0.05). HAPC patients along with the aggravation of different level, rCBF is reduced, in addition to the parietal cortex, temporal and occipital white matter, white matter rCBF differences between different parts of different condition have statistical significance ( P < 0.05). ROC curve was used to evaluate the diagnostic value of CTP and ASL. The two curves were close to each other, and CTP was slightly better than ASL. Conclusion With the progression of HAPC, cerebral blood flow decreased, blood volume increased, and average blood flow time prolonged in patients with different degrees of HAPC. CTP and ASL had similar effects, and the former had slightly better value. 摘要： 目的 研宄高原红细胞增多症(HAPC)CT脑灌注 (CTP) 的变化/核磁共振质子自旋标记技术 (3D-ASL) 的应用 价值并进行对比研宄。 方法 用多层螺旋 CT(MDCT) 研宄 22 例不同程度高原红细胞增多症患者的 CT 脑灌注的变 化; CT 全脑灌注技术与核磁共振质子自旋标记技术 (3D-ASL) 在高原红细胞增多症脑部血流动力学改变中的应用价 值的比较。 结果 HAPC 随病情加重, 大脑皮质和白质均脑血流量 (CBF) 呈下降趋势, 除额叶白质和颞叶白质外, 余部 位不同病情间差异均有统计学意义 ( P < 0.05); 随病情加重, 大脑各部位皮质和白质脑血容量 (CBV) 增加, 白质更为显 著, 且各部位不同病情间 CBV 差异均有统计学意义 ( P < 0.05); 随病情加重, 大脑各部位皮质和白质平均通过时间 (MTT) 均显著增加, 各部位不同病情间 MTT 差异均有统计学意义 ( P < 0.05); 不同程度 HAPC 患者随病情加重 ( P <0.05), 相对脑血流量(rCBF)降低, 除顶叶皮质、颞叶白质和枕叶白质外, 各部位不同病情间rCBF差异均有统计学意 义;通过 ROC 曲线来评价 CTP 和ASL两者的诊断价值, 两条曲线接近, CTP 略优于 ASL。 结论 不同程度HAPC患 者随着病情进展, 脑血流减低;血容量增加;血流平均通过时间延长; CTP 与 ASL 两种方法效果接近, 前者价值略优。

Using NMR to Test Molecular Mobility during a Chemical Reaction.

We evaluate critically the use of pulsed gradient spin-echo nuclear magnetic resonance to measure molecular mobility during chemical reactions. With raw NMR spectra available in a public depository, we confirm the boosted mobility during the click chemical reaction (Wang et al. Science 2020 369, 537-541) regardless of the order of magnetic field gradient (linearly increasing, linearly decreasing, random sequence). We also confirm boosted mobility for the Diels-Alder chemical reaction. The conceptual advantage of the former chemical system is that a constant reaction rate implies a constant catalyst concentration, whereas that of the latter is the absence of a paramagnetic catalyst, precluding paramagnetism as an objection to the measurements. The data and discussion in this paper show the reliability of experiments when one avoids convection, allows decay of nuclear spin magnetization between successive pulses and recovery of its intensity between gradients, and satisfies quasi-steady state during the time window to acquire each datum. Especially important is to make comparisons on the time scale of the actual chemical reaction kinetics. We discuss possible sources of mistaken conclusions that are desirable to avoid.

A built-in coil system attached to the inside walls of a magnetically shielded room for generating an ultra-high magnetic field homogeneity.

The homogeneity of the magnetic field generated by a coil inside a magnetic shield is essential for many applications, such as ultra-low field nuclear magnetic resonance or spin precession experiments. In the course of upgrading the Berlin Magnetically Shielded Room (BMSR-2) with a new inserted Permalloy layer of side length 2.87m, we designed a built-in coil consisting of four identical square windings attached to its inside walls. The spacings of the four windings were optimized using a recently developed semi-analytic model and finite element analysis. The result reveals a strong dependence of the field homogeneity on the asymmetric placement of the inner two windings and on the chosen material permeability value μs. However, our model calculations also show that these experimental variations can be counterbalanced by an adjustment of the inner winding positions in the millimeter range. Superconducting quantum interference device-based measurements yield for our implementation after fine adjustments of a single winding position a maximum field change of less than 10 pT for a total field of B0 = 2.3 µT within a 10cm region along the coil axis, which is already better than the residual field of the upgraded BMSR-2.1 after degaussing. Measurements of free spin precession decay signals of polarized Xe129 nuclei show that the transverse relaxation time for the used cell is not limited by the inhomogeneity of the new built-in coil system.

Simulation of nitrogen nuclear spin magnetization of liquid solved nitroxides.

Nitroxide radicals are widely used in electron paramagnetic resonance (EPR) applications. Nitroxides are stable organic radicals containing the N–O˙ group with hyperfine coupled unpaired electron and nitrogen nuclear spins. In the past, much attention was devoted to studying nitroxide EPR spectra and electron spin magnetization evolution under various experimental conditions. However, the dynamics of nitrogen nuclear spin has not been investigated in detail so far. In this work, we performed quantitative prediction and simulation of nitrogen nuclear spin magnetization evolution in several magnetic resonance experiments. Our research was focused on fast rotating nitroxide radicals in liquid solutions. We used a general approach allowing us to compute electron and nitrogen nuclear spin magnetization from the same time-dependent spin density matrix obtained by solving the Liouville/von Neumann equation. We investigated the nitrogen nuclear spin dynamics subjected to various radiofrequency magnetic fields. Furthermore, we predicted a large dynamic nuclear polarization of nitrogen upon nitroxide irradiation with microwaves and analyzed its effect on the nitroxide EPR saturation factor.

Tailored flavoproteins acting as light-driven spin machines pump nuclear hyperpolarization

The solid-state photo-chemically induced dynamic nuclear polarization (photo-CIDNP) effect generates non-Boltzmann nuclear spin magnetization, referred to as hyperpolarization, allowing for high gain of sensitivity in nuclear magnetic resonance (NMR). Well known to occur in photosynthetic reaction centers, the effect was also observed in a light-oxygen-voltage (LOV) domain of the blue-light receptor phototropin, in which the functional cysteine was removed to prevent photo-chemical reactions with the cofactor, a flavin mononucleotide (FMN). Upon illumination, the FMN abstracts an electron from a tryptophan to form a transient spin-correlated radical pair (SCRP) generating the photo-CIDNP effect. Here, we report on designed molecular spin-machines producing nuclear hyperpolarization upon illumination: a LOV domain of aureochrome1a from Phaeodactylum tricornutum, and a LOV domain named 4511 from Methylobacterium radiotolerans (Mr4511) which lacks an otherwise conserved tryptophan in its wild-type form. Insertion of the tryptophan at canonical and novel positions in Mr4511 yields photo-CIDNP effects observed by 15N and 1H liquid-state high-resolution NMR with a characteristic magnetic-field dependence indicating an involvement of anisotropic magnetic interactions and a slow-motion regime in the transient paramagnetic state. The heuristic biomimetic design opens new categories of experiments to analyze and apply the photo-CIDNP effect.

(Invited) Isotopically Engineered Silicon Testbeds for Advanced CMOS and Quantum Information

Silicon isotope engineering invokes a new paradigm into material science for nanoscale device applications [1]. The development of planer CMOS devices confronts an immediate issue of its downscaling limit, requiring a basal changeover to three-dimensional (3D) vertical transistors as a possible solution. General gate-all-around transistors involve formation of reliable gate-oxide film surrounding Si nanopillar structures. For the precise 3D process simulator, silicon isotopes are used as a self-diffusive marker for experimental determination of its model parameters. Recent advancement of atom probe tomography enables nearly atomic-resolution mass spectroscopy for 3D limited areas, together with great sensitivity to different Si isotopic mass [2]. By extending this technique to isotopically programmed Si nanopillars, individual self-diffused Si isotopes were visualized at MBE-grown isotopic layer interface [3, 4]. Recently, our quantitative evaluation revealed that Si self-diffusivity in gate-oxidized nanopillars was the same as the one measured for standard planar oxidation despite of its high interface-to-volume ratio [4]. In addition, silicon isotope engineering provides a crucial solution to eliminate unwanted decoherence for silicon quantum computers (QCs). Strong compatibility with industrial CMOS technology is expected to satisfy a scalability criterion significant for realizing practical QCs. In order to support the Si-QC research, we adopted silicon isotope engineering to tailor high-quality CVD-grown 28Si epi-wafers [1], where state-of-the-art Si-MOS nanoelectronic devices were implemented to demonstrate two-qubits operations encoded by single donor electron and nuclear spins [5]. Following an original Kane’s proposal, selective control of the electron spins was successfully achieved by adding a local gate bias thanks to the Stark tuning [6], while the nuclear-spin resonance has been recently shown to be driven by local electric fields in the presence of lattice strain [7]. Additionally, the isotopically enriched wafers were, in parallel, employed to demonstrate single and two spin-qubit operations in 28Si-MOS quantum dots (QDs) that were defined by standard CMOS lithography [8]. A series of proof-of-concepts experiments has given a boost to several proposals of Si-QC architectures based on advanced manufacturing technology [9]. Meanwhile, an alternative approach following conventional III-V QDs was made to obtain buried-type QDs utilizing strained-Si/SiGe quantum-well (QW) heterostructures, which are placed away from gate-oxide interface traps that can work as sources for charge noise to disturb spin-qubit operation. In fact, we accomplished isotope enrichment of Si-QW layer to efficiently remove magnetic nuclear-spin noise. As a consequence, the electron-spin dephasing time was prolonged to T 2 * ~ 20 ms for 28Si/SiGe QDs, where local single-spin controllability was introduced by a magnetic-field gradient from an on-chip micro-magnet [10]. These 28Si-QD devices amenable to several technical improvements have recorded the highest single-spin gate fidelities of 99.93% for 28Si/SiGe QDs [10] and 99.96% for 28Si-MOS QDs [11], respectively. Concurrently, it was revealed that inherent charge noise and/or residual nuclear-spin noise induced spin-resonance frequency fluctuations during the benchmark test executions. For higher-fidelity operations, including spin-qubit readout and initialization, low-energy excited states responsible for Si valley degeneracy should be also well-lifted by rendering the QD confinement atomically sharp. In these contexts, we will present recent development of high-quality 28Si/SiGe QWs appropriate for the silicon quantum information research. This work has been in part supported by MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118069228 and the Center for Spintronics Research Network, Keio University. The authors acknowledge fruitful collaborations with Yasuyoshi Nagai’s group, Seigo Tarucha’s group, Mark Eriksson’s group, Andrew Dzurak’s group and Andrea Morello’s group.[1] K. M. Itoh and H. Watanabe, MRS Communications 4, 143 (2014).[2] Y. Shimizu et al., J. Appl. Phys. 106, 076102 (2009).[3] T. Südkamp et al., J. Appl. Phys. 123, 161515 (2018).[4] R. Kiga et al., J. Appl. Phys. under review.[5] J.T. Mohonen et al., Nature Nanotechnol. 9, 986 (2014).[6] A. Laucht et al., Sci. Adv. 1, e1500022 (2015).[7] S. Asaad et al., arXiv:1906.01086.[8] M. Veldhorst et al., Nature Nanotechnol. 9, 981 (2014); M. Veldhorst et al., Nature 526, 410 (2015).[9] L.M.K. Vandersypen et al., npj Quantum Information 3, 34 (2017); M. Veldhorst et al., Nature Comm. 8, 1766 (2017); R. Li et al., Sci. Adv. 4, eaar3960 (2018).[10] J. Yoneda et al., Nature Nanotechnol. 13, 102 (2018).[11] C.H. Yang et al., Nature Electronics 2, 151 (2019).

NMR Studies of the Dynamics of 1D $$^3\hbox {He}$$ in $$^4\hbox {He}$$ Plated MCM-41

Pulsed NMR techniques have been used to study the dynamics of $$^3\hbox {He}$$ confined to the interior of the hexagonal nanochannels of MCM-41 for which the walls were coated with a monolayer of $$^4\hbox {He}$$ as determined by isotherm measurements. The $$^3\hbox {He}$$ was added afterward to form a 1D $$^3\hbox {He}$$ line density of about 0.1 $$\hbox {A}^{-1}$$ , corresponding to a Fermi temperature of $$T_{\mathrm{F}} \sim$$ 120 mK. A distinct and appreciable departure from the Curie law was observed for the nuclear spin magnetization below 0.5 K. The temperature dependence of the nuclear spin–lattice relaxation times, $$T_1$$ , for temperatures $$0.05<T<2.5$$ K, followed the expected linear behavior at low temperatures, and a peak was observed at $$T\sim 2T_{\mathrm{F}}$$ consistent with the Luttinger liquid theory as predicted by Polini et al. (Phys Rev Lett 98:266403, 2007). The observed temperature dependence of the nuclear spin–spin relaxation times, $$T_2$$ , differed considerably from that observed for $$T_1$$ , with a minimum at $$T= 0.8$$ K, similar to the tendency reported by Matsushita and colleagues.

Fast destruction of singlet order in NMR experiments.

Some nuclear spin systems support long-lived states, which display greatly extended relaxation times relative to the relaxation time of nuclear spin magnetization. In spin-1/2 pairs, such a long-lived state is given by singlet order, representing the difference of the population of the nuclear singlet state and the mean population of the three triplets. In many cases, the experiments with long-lived singlet order are very time-consuming because of the need to wait for singlet order decay before the experiment can be repeated; otherwise, spin order remaining from a previous measurement may lead to experimental artifacts. Here, we propose techniques for fast and efficient singlet order destruction. These methods exploit coherent singlet-triplet conversion; in some cases, multiple conversion steps are introduced. We demonstrate that singlet order destruction enables a dramatic reduction of the waiting time between consecutive experiments and suggest to use this approach in singlet-state Nuclear Magnetic Resonance (NMR) experiments with nearly equivalent spins.

Comparative Evaluation of the Photostability of Carbamazepine Polymorphs and Cocrystals

Carbamazepine (CBZ), a widely used antiepileptic, is known to be sensitive to light. The aim of this study was to evaluate the photostabilities of three cocrystals of CBZ (CBZ–succinic acid (SUC), CBZ–saccharin (SAC) form I, and CBZ–SAC form II) illuminated with a D65 fluorescent lamp compared with those of the conventional solid forms: CBZ polymorphs (forms I, II, and III). The order of discoloration determined using a colorimetric measurement was almost consistent with that of the degradation rates estimated using Fourier-transform infrared reflection–absorption spectroscopy, and these parameters of CBZ polymorphs increased in the order of form III, form I, and form II. CBZ–SUC and CBZ–SAC form I significantly suppressed the discoloration and degradation of CBZ compared with the raw CBZ, while CBZ–SAC form II facilitated the discoloration and degradation of CBZ. These results were supported by the results from the low-frequency Raman spectroscopy. The molecular mobility estimated using solid-state nuclear magnetic resonance 1H spin–lattice relaxation time strongly correlated with the degradation rate constant, indicating that molecular mobility significantly decreased following the formation of CBZ–SUC and CBZ–SAC form I and resulted in higher photostability. Overall, CBZ–SUC and CBZ–SAC form I are photostable forms and cocrystallization was proven to be an effective approach to improving the photostability of a photolabile drug.

Revealing the Emergence of Classicality Using Nitrogen-Vacancy Centers

The origin of classical reality in our quantum world is a long-standing mystery. Here, we examine a nitrogen-vacancy center in diamond evolving in the presence of its magnetic nuclear spin environment which is formed by the natural appearance of carbon ^{13}C atoms in the diamond lattice, to study quantum Darwinism-the proliferation of information about preferred quantum states throughout the world via the environment. This redundantly imprinted information accounts for the perception of objective reality, as it is independently accessible by many without perturbing the system of interest. To observe this process, we implement a novel dynamical decoupling scheme that enables the measurement and control of several nuclear spins (the environment E) interacting with a nitrogen vacancy (the system S). Our experiment demonstrates that, in the course of the decoherence of S, redundant information is indeed imprinted onto E, giving rise to incipient classical objectivity-a consensus recorded in redundant copies, and available from the fragments of the nuclear spin environment E, about the state of S. This provides the first laboratory verification of the process responsible for the emergence of the objective classical world from the underlying quantum substrate.

Synchronous measurement of inertial rotation and magnetic field using a K−Rb−Ne21 comagnetometer

We propose a method for synchronous measurement of inertial rotation and magnetic field based on the nuclear spin magnetization of the $^{21}\mathrm{Ne}$ self-compensation magnetic field and enhancement of the rotation signal in a $\mathrm{K}\text{\ensuremath{-}}\mathrm{Rb}{\text{\ensuremath{-}}}^{21}\mathrm{Ne}$ comagnetometer. Under different working temperature conditions, we study the operation of the system as a self-compensation comagnetometer. Using the formulated Bloch equations, the magnetic field and inertial rotation are simultaneously measured by the transient and steady responses in a single probe beam configuration. The measurement of earth rotation projection on the horizontal plane from $\ensuremath{-}5.59\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ to $5.59\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\phantom{\rule{0.28em}{0ex}}\mathrm{rad}/\mathrm{s}$ based on the steady signal and measurement of the magnetic field ranging from 0.016 to 1.760 nT based on the transient signal have been presented. Furthermore, the simultaneous measurements of angular velocity varying from $\ensuremath{-}4.01\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ to $5.37\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\phantom{\rule{0.28em}{0ex}}\mathrm{rad}/\mathrm{s}$ with an accuracy of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\phantom{\rule{0.28em}{0ex}}\mathrm{rad}/\mathrm{s}$ and a magnetic field changing from 0.048 to 0.128 nT with an accuracy of 0.01 nT have also been demonstrated.