Scalable Spin Amplification with a Gain over a Hundred

We propose a scalable and practical implementation of spin amplification which does not require individual addressing nor a specially tailored spin network. We have demonstrated a gain of 140 in a solid-state nuclear spin system of which the spin polarization has been increased to 0.12 using dynamic nuclear polarization with photoexcited triplet electron spins. Spin amplification scalable to a higher gain opens the door to the single spin measurement for a readout of quantum computers as well as practical applications of nuclear magnetic resonance (NMR) spectroscopy to infinitesimal samples which have been concealed by thermal noise.Comment: 6 pages, 7 figure

Magnetic-field cycling instrumentation for dynamic nuclear polarization-nuclear magnetic resonance using photoexcited triplets

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Akinori Kagawa, Makoto Negoro, Kazuyuki Takeda, and Masahiro Kitagawa, Review of Scientific Instruments 80, 044705 (2009) and may be found at https://doi.org/10.1063/1.3123346

A Ku band pulsed electron paramagnetic resonance spectrometer using an arbitrary waveform generator for quantum control experiments at millikelvin temperatures

We present a 17 GHz (Ku band) arbitrary waveform pulsed electron paramagnetic resonance spectrometer for experiments down to millikelvin temperatures. The spectrometer is located at room temperature, while the resonator is placed either in a room temperature magnet or inside a cryogen-free dilution refrigerator; the operating temperature range of the dilution unit is from ca. 10 mK to 8 K. This combination provides the opportunity to perform quantum control experiments on electron spins in the pure-state regime. At 0.6 T, spin echo experiments were carried out using ?-irradiated quartz glass from 1 K to 12.3 mK. With decreasing temperatures, we observed an increase in spin echo signal intensities due to increasing spin polarizations, in accordance with theoretical predictions. Through experimental data fitting, thermal spin polarization at 100 mK was estimated to be at least 99%, which was almost pure state. Next, to demonstrate the ability to create arbitrary waveform pulses, we generate a shaped pulse by superposing three Gaussian pulses of different frequencies. The resulting pulse was able to selectively and coherently excite three different spin packets simultaneously - a useful ability for analyzing multi-spin system and for controlling a multi-qubit quantum computer. By applying this pulse to the inhomogeneously broadened sample, we obtain three well-resolved excitations at 8 K, 1 K, and 14 mK

Cocrystalline matrices for hyperpolarization at room temperature using photoexcited electrons

We propose using cocrystals as effective polarization matrices for triplet dynamic nuclear polarization (DNP) at room temperature. The polari-zation source can be uniformly doped into cocrystals formed through acid–acid, amide–amide, and acid–amide synthons. The dense-packing crystal structures, facilitated by multiple hydrogen bonding and – interactions, result in extended T1 relaxation times, enabling efficient polarization diffusion within the crystals. Our study demonstrates the successful polarization of a DNP-magnetic resonance imaging molecular probe, such as urea, within a cocrystal matrix at room temperature using triplet-DNP

Dissolution Dynamic Nuclear Polarization at Room Temperature Using Photoexcited Triplet Electrons

Dissolution dynamic nuclear polarization (DNP) has recently gained attention as a method to enhance the sensitivity of liquid NMR spectroscopy and MRI. We demonstrate dissolution of the sample hyperpolarized by DNP using photoexcited triplet electrons in 0.38 T at room temperature. The achieved polarization of 0.8% is 6100 times as high as that at thermal equilibrium under the condition. The result is an important step for DNP using photoexcited triplet electrons to become widely used in chemical and biomedical research

13C pulsed dynamic nuclear polarization using pentacene or NV- centers in diamond at room temperature

我々が超高感度溶液NMRを実現したペンタセンをドープした[calboxyl-13C]安息香酸の系と、近年世界中で盛んに研究されているNV中心を含むダイヤモンドの二つの系でpulsed-DNPによる13Cスピンの直接室温超偏極に成功した。Pulsed-DNPシーケンス一回あたりの13Cスピンへの偏極移動確率が、ダイヤモンドの系は安息香酸の系に比べて約9倍高いが、核スピンT1は5倍短く、またESRスペクトルが2倍ブロードであることなどに起因して、到達偏極率が低くなる。最終的に、ダイヤモンド中に天然存在比で存在する13Cスピンでは0.01%、[calboxyl-13C]安息香酸中では0.13%の偏極率を得ることができた。3rd IFQM

Room Temperature Hyperpolarization of Polycrystalline Samples with Optically Polarized Triplet Electrons: NV centers versus Pentacene

Dynamic nuclear polarization (DNP), a technique to transfer spin polarization from electrons to nuclei, has been studied since its early discovery [1] and has opened the way for high sensitive nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging. In "conventional" DNP, which uses thermally-polarized unpaired electrons as the source of polarization, the DNP enhancement factor is limited to γe/γn, where γe(n) are the gyromagnetic ratios of the electron (nuclear) spins. In DNP using the paramagnetic electrons in thermal equilibrium, experiments need to be performed at cryogenic temperature to increase the electron-spin polarization as much as possible. Conversely, the spins of optically created electrons in the triplet state can have much higher polarization than their thermal equilibrium value, DNP using the triplet state, referred to as triplet DNP, can lead to nuclear hyperpolarization beyond the limit of the conventional DNP using thermal electron polarization. Furthermore, experiments can be carried out at room temperature, by irradiating the sample with laser light. Recently, DNP of an ensemble of 13C nuclear spins using negatively charged nitrogen-vacancy (NV−) color centers in a bulk diamond single crystal has been demonstrated at room temperature and the 13C polarization of 6 % has been achieved via the combination of the thermal mixing and the solid effect [2]. DNP using NV− in powdered microdiamonds has been reported by Ajoy et al., who took advantage of the reduced width of the anisotropic electron spin resonance powder pattern of the NV− centers at the magnetic field of ca. 30 mT [3]. However, triplet DNP is much older and achieved a 1H polarization of 34 % at room temperature and a magnetic field of 0.4 T using pentacene in p-terphenyl crystal [4]. Even though triplet DNP in both systems, NV- centers and pentacene, relies on the transfer of spin polarization from optically hyperpolarized triplet electrons to nuclei , there are important differences. While the NV- center has an electronic triplet ground state and is therefore paramagnetic, pentacene has an electronic singlet ground state, is diamagnetic, and only becomes paramagnetic through optical excitation into a triplet state. On the other hand, the zero-field splitting parameter D for pentacene is only half as large as in NV- centers, which is an advantage when disordered powder is used as a sample. In this work, we compare triplet-DNP of NV− centers in diamond and pentacene doped in [carboxyl-13C] benzoic acid (PBA) in polycrystalline samples at room temperature [5]. In the DNP experiments, the integrated solid effect (ISE) was used to transfer the polarization from electrons to nuclei. The ISE employs microwave irradiation and external magnetic-field sweep, so that the Hartmann–Hahn matching is implemented between the electron spins in the rotating frame and the nuclear spins in the laboratory frame. We study the behavior of the 13C polarization buildup in terms of the polarization efficiency of the transfer from the electron to nuclei, exchange rate, and the 13C spin diffusion. As a result, we obtained the 13C polarization of 0.01 % in the microdiamonds, and of 0.12 % in PBA at room temperature in a magnetic field of 0.4 T by using the integrated solid effect and the obtained exchange rate was 0.87 % for microdiamonds and 3.5 % for PBA. The 13C polarization enhancements for the diamond and the PBA were 300 and 3600 compared to the thermal NMR polarization. Besides the initial polarization transfer from the triplet electron to the nuclei, we also shed light on the process of nuclear spin-spin diffusion, which distributes the hyperpolarization within the sample.2021 MRS Fall Meeting & Exhibi