Mechanically Detected Nuclear Magnetic Resonance at Room Temperature and Normal Pressure

Mechanically detected magnetic resonance (MMR) is a new technique for detecting electron or nuclear spin signals. All preceding experiments have been carried out in a <10⁻³Torr vacuum at room temperature or at low temperatures down to 6 K. In this article the first MMR experiments at normal pressure and room temperature are presented. The mechanically detected NMR signals resulted from ammonium nitrate and ammonium sulfate. In addition, techniques for determiningT₁andT_1ρwith mechanical experiments were developed. IfT_1ρis not more than two or three times smaller thanT₁, an inversion-recovery technique, first used for the detection of¹⁹F spins at low temperatures, can be used. It could be shown that this technique also works in principle at room temperature.     

Quantum Logic Gates and Nuclear Magnetic Resonance Pulse Sequences

There has recently been considerable interest in the use of nuclear magnetic resonance (NMR) as a technology for the implementation of small quantum computers. These computers operate by the laws of quantum mechanics, rather than classical mechanics and can be used to implement new quantum algorithms. Here we describe how NMR in principle can be used to implement all the elements required to build quantum computers, and draw comparisons between the pulse sequences involved and those of more conventional NMR experiments.     

Liquid Nuclear Magnetic Resonance Implementation of Quantum Computation in Subspace

Based on the logical labelling method, we prepare an effective pure state in a subsystem of a three spin system via liquid nuclear magnetic resonance technique. Then with this subspace effective pure state we implement the Deutsch-Jozsa algorithm. The tomography for the subspace effective pure state and the corresponding spectrum of the output for the Deutsch-Jozsa algorithm agree with theoretical predictions, which shows that we have successfully implemented the Deutsch-Jozsa algorithm in a subsystem of a nuclear spin system and demonstrated a subspace quantum computation.     

Demonstration of Quantum Entanglement Control Using Nuclear Magnetic Resonance

With the two forms of the quantum entanglement control, the quantum entanglement swapping and preservation are demonstrated in a three-qubit nuclear magnetic resonance quantum computer. The pseudopure state is prepared to represent the quantum entangled states through macroscopic signals. Entanglement swapping is directly realized by a swap operation. By controlling the interactions between the system and its environment,we can preserve an initial entangled state for a longer time. The experimental results are in agreement with the experiment.     

Geometric Quantum Discord of a Two-Qutrit System Under Decoherence at Finite Temperature

The dynamics and protection of geometric quantum discord (GQD) for a two-qutrit system under amplitude damping channel with finite temperature have been studied in detail. By using of a lower bound of GQD, numerical results show that the GQD dynamics suffering from amplitude damping channels is more robust against the decoherence at lower temperature. Moreover, by combining weak measurement with measurement reversal, we have also investigated the protecting of the GDQ for a two-qutrit system under decoherence. It is found that the measurement technique can effectively protect the GQD against decoherence at lower temperature, but fails to protect GQD at higher temperature of channel.     

Quantum Spin Systems at Positive Temperature

We develop a novel approach to phase transitions in quantum spin models based on a relation to their classical counterparts. Explicitly, we show that whenever chessboard estimates can be used to prove a phase transition in the classical model, the corresponding quantum model will have a similar phase transition, provided the inverse temperature β and the magnitude of the quantum spins satisfy . From the quantum system we require that it is reflection positive and that it has a meaningful classical limit; the core technical estimate may be described as an extension of the Berezin-Lieb inequalities down to the level of matrix elements. The general theory is applied to prove phase transitions in various quantum spin systems with . The most notable examples are the quantum orbital-compass model on and the quantum 120-degree model on which are shown to exhibit symmetry breaking at low-temperatures despite the infinite degeneracy of their (classical) ground state.     

Nuclear Magnetic Resonance in Industry

It is the author's intention to demonstrate progress in the application of nuclear magnetic resonance (NMR) in industry over a period of nearly 30 years.     

Nuclear Magnetic Resonance Imaging

Abstract

The advent of X-ray computed tomographic (CT) imaging revolutionized the evaluation of a wide range of pathological conditions by producing thin tomographic sections through the body with remarkable anatomical detail. By the early 1980s, X-ray CT was an established imaging modality, and a second computer-based form of imaging was emerging from the research laboratory into the clinic. The second wave of the imaging revolution has been the development of NMR imaging (usually referred to as magnetic resonance imaging, or MRI) and its acceptance as the preferred modality for much neurological and musculoskeletal imaging. MRI's soft-tissue contrast and resolution is superior to that of other imaging techniques, the low NMR signal from bone renders it superior to X-ray CT in many cases for images of the head and spine, it has more varied contrast possibilities than CT, and can image in any plane without repositioning the patient. In spite of the high cost of purchase and installation, MR scanners are proliferating rapidly, and techniques and clinical applications for MR imaging continue to advance at an equally rapid rate.     

Thermal Quantum Discord in Pure Dzyaloshinskii-Moriya Model with Magnetic Field

We investigate the effects of the directions of Dzyaloshinskii-Moriya (DM) interaction vector and magnetic field on the quantum discord in the pure DM model. For different directions of DM vector, we find that there are different optimal parameter components of magnetic field. Moreover, we find that the optimal parameter components rules are the same for the Hamiltonian H₁ and H₂. According to the rules, for a certain axial DM vector, we can get the maximal quantum discord by adjusting the direction of the external magnetic field, which is feasible under the current experimental technology.     

Chemical Applications of Nuclear Magnetic Resonance at High Fields

Abstract

A review confined to nuclear magnetic resonance measurements in a particular field-strength range needs some justification. Although the advent of the superconducting magnet in NMR presents quite novel problems for the spectrometer designer, and involves the user in some new operating techniques, the jump from 100 MHz (for proton resonances) to 220 MHz does not involve any new form of spectroscopy, any more than did the earlier advances from 40 MHz to 60 MHz, and thence to 100 MHz. The advantages in spectrometer performance which result from using a superconducting magnet are of degree, not of kind, and one is not called upon to learn anything new about NMR in order to interpret the spectra; indeed, the effect in many cases is to simplify the interpretation, so that a sophisticated quantum-mechanical approach is less often needed.     

Nuclear Magnetic Resonance Studies in Gases

There are several reasons why nuclear magnetic resonance (NMR) studies in gases are important. At low pressures the interactions in the gas phase are essentially governed by two body collisions. It is therefore possible to study the intermolecular forces between two molecules approaching one another during collision from their influence on the chemical shifts of the nuclei of the molecules under considerations. The experimental measurements allow one to learn how the chemical shift is perturbed because of the presence of other molecules. This knowledge can then be transferred to interpret solvent effects in condensed phases and for detection of any solvent-solute interactions in such systems.     

Detecting Quantum Dissonance and Discord in Exact Dynamics of qubit Systems

In this paper, we evaluate the quantum and classical correlations in exact dynamics of qubit systems interacting with a common dephasing environment. We show the existence of a sharp transition between the classical and quantum loss of correlations during the time evolution. We show that it is possible to exploit a large class of initial states in different tasks of quantum information and processing without any perturbation of the correlations from the environment noisy for large time intervals. On the other hand, we include the dynamics of a new kind of correlation so-called quantum dissonance, which contains the rest of the nonclassical correlations. We show that the quantum dissonance can be considered as an indicator to expect the behavior of the dynamics of classical and quantum correlations in composite open quantum systems.     

A Superconducting Quantum Interference Device Measurement System for Ultra Low-Field Nuclear Magnetic Resonance

We describe a superconducting quantum interference device (SQUID)-based nuclear magnetic resonance (NMR) spectrometer operating at ultralow magnetic fields far below the Earth’s field. The spectrometer consists of a helium-cooled magnetic sensor system and two Helmholtz coils, one for pre-polarizing the sample by fields of up to 5 mT, and one for the detection in fields of the nanotesla and microtesla range. The spectrometer represents the current state of the art in ultralow-field NMR and enables the observation of phenomena that are difficult or impossible to achieve by a conventional NMR setting. In particular, one can obtain broad band spectra covering different nuclei, such as ¹H and ³¹P, with a frequency resolution in the millihertz range, observe the variation of their heteronuclear coupling with the detection field strength, and investigate relaxation processes that reflect molecular dynamics in the millisecond range.     

A Lower Bound of Quantum Discord for 2-Qutrit Systems

We study the lower bound of quantum discord for 2-qutrit systems. By computing the mutual information and the classical correlations of a class of states for 2-qutrit system, an analytical and computable lower bound of discord has been derived. By selecting different coefficients as examples, we can compute the lower bound of discord for 2-qutrit systems directly. The result can be generalized to the case of high-dimensional quantum state and will help us understand and explore the discord of the high-dimensional state.     

一种基于室温工作的量子点光电探测器的微光读出和应用研究

针对量子点光电探测器线列进行微光检测研究,量子点探测器采用AlAs/GaAs/AlAs双势垒结构,GaAs宽阱中分别有一个InAs量子点(QDs)和In_0.15Ga_0.85As量子阱(QW),建立一个简单的器件模型进行分析。常温下,在632.8 nm He-Ne激光照射下,当光功率为 0.01 pW时,器件偏压-0.5 V,积分时间80.2 μs,电压响应率达到7.0×1011 V·W-1,具有非常高的灵敏度,这种光电探测器在300 K温度下可以探测光功率小于10-14 W极弱光。以这种量子点光电探测器为核心研制的高灵敏度光谱仪和分子超光谱系统结合对生物组织样本进行检测,研制了一种图谱相互验证,互为校正的生物组织光谱测量系统。     

Viscosity Correlations with Nuclear (Proton) Magnetic Resonance Relaxation in Oil Disperse Systems

Using nuclear (proton) magnetic resonance relaxometry (NMRR) was studied oil disperse systems. Dependences of NMR–relaxation parameters—spin–lattice T_1i, spin–spin T_2i relaxation times, proton populations P_1i and P_2i, and petrophysical correlations were received for light and heavy oils. Experimental results are interpreted on the base of structure-dynamical ordering of oil molecules with structure unit formation.     

采用超导量子干涉组件在微特斯拉磁场下获取超极化~3He的核磁共振波谱和影像(英文)

该文以超导量子干涉元件研究光激发氦三极化气体的低磁场磁共振与造影术.使用圆偏极化雷色光将氦三气体极化,超导量子干涉元件磁共振与造影之测量是以磁通耦合方式来进行,超导量子干涉元件是用铋锶钙铜氧高溫超导罐来隔离环境噪音.此方法测得的磁共振信号与影像相较于直接将样品置于杜瓦瓶下方有较高的信噪比,当样品无法靠近感测元件时,此装置具高信噪比特色.磁通耦合方式的超导量子干涉元件低磁场磁共振与造影术及其氦三极化气体的肺部造影在学术与应用上是相当有趣.     

Two-Dimensional Frequency-Relaxation Nuclear Magnetic and Nuclear Quadrupole Resonance Spectroscopies

Russian Physics Journal -