Hyperpolarization and NMR dtection on a diamond quantum chip
Analytical Chemistry
Inorganic Molecular Chemistry - Synthesis and Characterisation
Solid State and Surface Chemistry, Material Synthesis
Organic Molecular Chemistry - Synthesis and Characterisation
Final Report Abstract
Throughout the funding period of the Walter Benjamin Position “Hyperpolarization and NMR detection on a quantum diamond chip,” we significantly advanced our understanding on the utilization of spin defects in diamonds and alternative materials, for enhanced nanoscale NMR detection. The main goal of the project was to demonstrate polarization transfer from optically pumped ensembles of NV centers in diamond to nuclear spins outside the diamond lattice and their consequent enhanced NMR detection. The outcomes from the research met most of the objectives of the project and created a base for future discoveries that reach beyond the original research goals. Specifically, the key accomplishments of the project are as follows: Spin Polarization Transfer in Diamond Systems: The project's primary outcomes, presented in Rizzato et al., PRApplied 2022 1, include successful spin polarization transfer from ensembles of shallow NV centers to 13 C nuclear spins inside the diamond crystal and to 1 H and 19 F nuclei outside the diamond. This achievement is noteworthy as it highlights the potential of utilizing ensembles of NV centers to transfer spin polarization to nuclear spins positioned unambiguously outside the diamond and even across additional interfaces, such as AlO2 deposited on the diamond surface. Second, the sample was designed to have a well-defined geometry, enabling the precise measurement of spin polarization transfer rates. These were then utilized to forecast potential scenarios for achieving effective nuclear spin hyperpolarization for enhanced NMR detection. Nonetheless, processes such as spin relaxation and diffusion, particularly impacting nuclei at a distance, posed a challenge to detect a substantially enhanced NMR signal of target nuclei. This called for a re-evaluation of NV-diamond hyperpolarization methods and a detailed examination of the technology's design to achieve the final objectives. Exploration of Spin Defects in hBN: Motivated by these findings and drawing from recent studies on new spin defects in alternative materials 2–4, we turned our attention to hexagonal Boron Nitride (hBN). We were particularly interested in its stable two - dimensional characteristics, with the potential for a closer proximity between the polarizer and the target, and the possibility of reducing spin depolarization caused by surface defects. Our breakthroughs, detailed in Rizzato et al., Nat. Commun., 2023, included extending the coherence time of V B - spins, showcasing the possibility of spin manipulation and the realization of spinlock experiments which positions hBN as an emerging platform for spin hyperpolarization 5,6. Surface-NMR Technique Development: In parallel to the activity on hyperpolarization and utilizing the same sample-design, we established a powerful surface-NMR technique, demonstrating its potential to detect NMR signals from a small number of nuclear spins, for instance on a self-assembled monolayer grown on the diamond in just a few minutes of acquisition time 7. Molecular Confinement for NV-NMR Spectroscopy: We investigated using Metal- Organic Frameworks (MOFs) on diamond chips for molecular confinement within a porous medium, enabling the detection of liquid sample NV-NMR signals 8. This initial experiment also indicates MOF-based molecular confinement as a promising avenue for spin hyperpolarization on a diamond quantum chip. Impact of Electrolytes on NV-centers: Our study revealed that diamagnetic electrolytes can influence NV sensors and surface paramagnetic species on diamonds, enhancing their spin lifetimes9. This finding is crucial for improving NV-NMR techniques, advancing NV-based hyperpolarization, and understanding the nanoscale dynamics at solid -liquid interfaces. Quantum Sensing with Spinlock Sequences: Our research into spinlock-based polarization transfer methods suggests that the same protocols may also be used for sensing and that they can even outperform standard pulsed dynamic decoupling sequences. This advancement holds potential for the application of NV-NMR sensing at high magnetic fields, a current challenge for the enhancement of the method’s resolution and sensitivity. These interrelated studies have significantly contributed to the field of nanoscale NMR spectroscopy and have laid the groundwork for the creation of innovative spin - hyperpolarization platforms. These advancements promise to enhance NMR spectroscopy by means of quantum technology. Moving forward, our focus will be on refining these pioneering techniques and broadening their applications, which could revolutionize NMR spectroscopy and pave the way for new quantum technology developments.
Publications
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Polarization Transfer from Optically Pumped Ensembles of N-
Rizzato, R.; Bruckmaier, F.; Liu, K.S.; Glaser, S.J. & Bucher, D.B.
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Surface NMR using quantum sensors in diamond. Proceedings of the National Academy of Sciences, 119(5).
Liu, Kristina S.; Henning, Alex; Heindl, Markus W.; Allert, Robin D.; Bartl, Johannes D.; Sharp, Ian D.; Rizzato, Roberto & Bucher, Dominik B.
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Using Metal–Organic Frameworks to Confine Liquid Samples for Nanoscale NV-NMR. Nano Letters, 22(24), 9876-9882.
Liu, Kristina S.; Ma, Xiaoxin; Rizzato, Roberto; Semrau, Anna L.; Henning, Alex; Sharp, Ian D.; Fischer, Roland A. & Bucher, Dominik B.
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Extending the coherence of spin defects in hBN enables advanced qubit control and quantum sensing. Nature Communications, 14(1).
Rizzato, Roberto; Schalk, Martin; Mohr, Stephan; Hermann, Jens C.; Leibold, Joachim P.; Bruckmaier, Fleming; Salvitti, Giovanna; Qian, Chenjiang; Ji, Peirui; Astakhov, Georgy V.; Kentsch, Ulrich; Helm, Manfred; Stier, Andreas V.; Finley, Jonathan J. & Bucher, Dominik B.
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The Role of Electrolytes in the Relaxation of Near-Surface Spin Defects in Diamond. ACS Nano, 17(11), 10474-10485.
Freire-Moschovitis, Fabian A.; Rizzato, Roberto; Pershin, Anton; Schepp, Moritz R.; Allert, Robin D.; Todenhagen, Lina M.; Brandt, Martin S.; Gali, Adam & Bucher, Dominik B.
