Underwater Quantum Sensing with Solid-State Nuclear Spins
Abstract
Approved for Public Release-Quantum sensing and quantum computing, collectively part of quantum information science (QIS), are poised to become essential for United States Navy capabilities across national security, cybersecurity, and strategic technological advantage within the coming years, though all current QIS platforms face a variety of stubborn challenges to practical field deployment. Some of these challenges involve basic physics and materials science: fragile quantum states must be preserved for long durations for effective sensing and computation, but outside of highly controlled (magnetically shielded, cryogenic) environments, coherence in existing materials platforms is unusably short. Meanwhile, the supporting hardware required by current methods and materials makes the overall instrument expensive, bulky, and fragile, and thus ill-suited to portable deployment and use in harsh environments (e.g. underwater) as is crucial to the Navy. Newly developed techniques and materials investigated by PI Ajoy pose to overcome these challenges and help improve various other QIS platforms. Early work from PI Ajoy has demonstrated that hyperpolarized nuclear spins in solids, specifically 13C nuclear spins in diamond polarized (initialized) by Nitrogen Vacancy (NV) centers, exhibit excellent properties for quantum sensing. The strong coupling between 13C nuclei and their effective quantum controllability via off-the-shelf hardware allows them to be driven into stable rigid "orbit" spin trajectories, giving effective coherence time T2 >90s at room temperature. These spins are quasi-continuously read out in radio-frequency via nuclear magnetic resonance (NMR) techniques. These properties enable quantum sensing magnetometry at high signal-to-noise ratio through cross-correlation data processing approaches that recover weak electromagnetic (EM) signals. This portends their use as a readily deployable sensor platform for use in underwater environments with all supporting instrumentation in an inexpensive, compact, and resilient self-contained package. In parallel, these hyperpolarized nuclei will serve as a test-bench for fundamental investigations into the origins of noise and decoherence in QIS platforms. Our first objective is to develop high-sensitivity, long-coherence underwater quantum sensors. In preliminary results, hyperpolarized nuclear spins in diamond have sensed EM fields at sensitivity better than competing quantum sensors in frequency ranges of naval relevance, namely 1 Hz to 50kHz which encompasses ELF, ULF, and VLF. Envisioned quantum sensors promise superior sensitivity, robust noise rejection, and potential for deployment as incompressible units suitable for deep-sea operations, including for use in fixed or portable arrays of multiple sensors. Our second objective is to apply quantum sensing by hyperpolarized nuclear spins to fundamental investigations on the sources of noise and decoherence in this (NV-13C) QIS material platform. Recent work has demonstrated fine quantum control of ensembles of hundreds to thousands of nuclear spins surrounding each NV center into stable many-body spin textures. The resulting 13C NMR signals provide spatially resolved data on decoherence over multiple nanometers. We will extend this result into techniques for high-resolution, nanoscale spatiotemporal mapping of sensing fields, with the use of inverse Laplace transforms to discern relaxation phenomena and identify factors affecting them. A key goal is to uncover channels of electron and phonon relaxation, and the interplay or cooperative effects between different classes of mechanisms, i.e. multi-spectral spin processes. Through this effort, we expect to gain insights on how to reduce noise and protect quantum coherence in NV-center doped diamonds and other QIS hardware platforms, and thereby improve the performance of quantum sensors and information devices.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 08, 2024
- Source ID
- N000142412185
Entities
People
- Ashok Ajoy
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents