Electron-Nuclear spin clusters for Quantum Sensing by Resonance Matching

The holy grail of quantum information science (QIS) is control over polarization and spin coherence in water, which is the universal medium of biology and an adversarial environment for quantum sensing. Our approach is to gain an understanding and control over the microscopic and quantum mechanical structure of multi-electron-nuclear spin clusters. Within these clusters, strong and asymmetric coupling between two or more electrons can be designed to excite the intended electron-electron-nucleus (e-e-n) triple flip quantum transition by e-e-n resonance energy matching. Efficient e-e-n coupling may underlie quantum sensing and/or multi-electron dynamic nuclear polarization (ME-DNP) induced NMR signal enhancements to report on the electronic structure property of target nuclear spins, molecular distances and motion, as well as to enhance the 1H NMR relaxivity of water in the presence of nanoparticle-Gd chelated contrast agents that would result in greater MRI contrast. Understanding and controlling polarization transfer between electron and nuclear spins is also critical for optical initialization of electron spin hyperpolarization to achieve quantum sensing and storage of nuclear spin signal.

Knowledge Gap?

The microscopic origin of polarization and coherence transfer is not well understood, making it difficult to control and enhance quantum sensing efficiencies. In a recently published study, we discovered that a large fraction of P1 centers in diamond are exchange coupled. This is an important insight as these structures must be considered when designing optimal quantum sensors for longer range analyte sensing or for designing brighter MRI contrast agent by quantum resonance matching. Work is underway to design different electron spin cluster geometries using diamond and gold nanoparticles, as well as paramagnetic crystals to achieve efficient analyte enhancement and detection by quantum resonance matching.

Han Lab Strategy?

The strategy of the Han lab is to design novel coupled electron-nuclear spin clusters, and to perform DNP-enhanced NMR near the optical limit that permits the initialization at pure spin state in steady state, facilitates quantum operation and permits the study of spin dynamics and physics in the absence of certain thermal noise. The design, triaging and optimization of coupled electron-nuclear spin clusters to achieve long-range quantum sensing requires dual NMR and EPR manipulation, detection, and characterization tools at high magnetic fields. The goal–and the Han lab already has exciting leads to this end–is to utilize the knowledge gained in these extreme limits to develop quantum sensing applications in water and under biologically relevant conditions.

Unique Han Lab Tools and Concepts: