Quantum Sensing

Utsab Banerjee (Technical University of Munich, Germany)

LinkedIn: Utsab Banerjee, X: @UtsabBan1729, BlueSky: @utsab1729.bsky.social

Abstract: Nitrogen-vacancy (NV) centres in diamond are powerful quantum sensors capable of performing NMR spectroscopy on spin systems far beyond the reach of conventional inductive detection. Positioned a few nanometers beneath the diamond surface, these optically addressable defects sense statistical nuclear spin fluctuations from nanoscale volumes, circumventing the Boltzmann polarisation bottleneck that demands large samples and high magnetic fields. Deuterium (²H) is an ideal target: its quadrupolar Pake patterns encode molecular geometry and dynamics, with intrinsic breadths naturally matching NV-accessible spectral resolution. Resolving such lineshapes at the nanoscale has remained an outstanding challenge.
Here, we demonstrate nanoscale ²H NMR using shallow NV centre ensembles in an isotopically enriched diamond chip, at magnetic fields orders of magnitude lower than conventional spectrometers. Correlation spectroscopy protocols built on dynamical decoupling sequences yield powder-like ²H quadrupolar Pake patterns from deuterated samples on the diamond surface, directly comparable to bulk solid-state ²H NMR.
NV-NMR delivers a spin sensitivity many orders of magnitude beyond conventional inductive detection while retaining the rich spectral information of the quadrupolar interaction, fittable with standard solid-state NMR software. Variable-temperature measurements reveal distinct interfacial physics: the polymer shows suppressed dynamics consistent with an elevated local glass-transition temperature at the diamond surface, while the molecular solid undergoes a progressive lineshape collapse tracking its solid-liquid phase transition. This work establishes NV-based quadrupolar ²H NMR as a new sensing modality for probing molecular dynamics at surfaces and interfaces, with ultimate prospects for single-molecule detection.

Rohma Khan (CUNY City College of New York, CUNY Graduate Center, United States)

Bluesky: @gbalavoi.bsky.social‬

Abstract: Characterization of nanoscale confinement of liquids via quantum sensing can overcome the sensitivity, spatial, and temporal limitations of other measurement techniques, allowing deeper understanding of dynamics central to areas spanning geophysics, tribology, catalysis, polymer science, and biology. Using shallow nitrogen vacancy (NV) centers as our quantum sensors we probe the molecular dynamics of water molecules confined within engineered ~5-nm-tall channels formed by a hexagonal boron nitride (hBN) structure on the diamond surface. Our resultant NV-enabled nuclear magnetic resonance spectra of confined water protons reveal a reduced H2O self-diffusivity, orders of magnitude lower than that in bulk water. Correlation measurements show us long lasting nuclear spin coherences, indicative of molecular dynamics intermediate between bulk water and ice. Molecular dynamics modeling indicate cluster formations may arise from accumulation of surface charge and carrier injection into the fluid under laser illumination. Our next step is the extension of these experiments to variable temperatures with preliminary findings showing narrowing of our NV NMR Spectra as we approach freezing point.

Amaria Javed (NYU Abu Dhabi, United Arab Emirates)

Abstract: This talk presents our ongoing work on NV-diamond-based quantum sensing at the Center for Quantum and Topological Systems (CQTS) at NYU Abu Dhabi, with a focus on optical techniques for spin state readout and signal enhancement. Nitrogen-Vacancy (NV) centers in diamond are point defects that serve as atomic-scale quantum sensors, offering remarkable sensitivity to magnetic and electric fields, temperature, and strain. These color centers exhibit spin-dependent fluorescence under green laser excitation, enabling optical initialization and readout of their quantum state even at room temperature.
At the core of our experimental approach is Optically Detected Magnetic Resonance (ODMR), a technique that uses changes in NV center fluorescence to measure shifts in spin transitions, revealing information about the surrounding environment. We are currently building a custom NV-based sensing setup, which involves laser excitation at 532 nm, microwave control of spin transitions, and efficient fluorescence detection via optical filters and photodetectors.
Our work aims to optimize the optical alignment, fluorescence collection efficiency, and stability of the system for robust quantum sensing applications. We explore methods to enhance contrast in ODMR spectra, increase sensitivity, and suppress background noise, which are critical for real-time, high-resolution measurements. These efforts lay the foundation for emerging applications in nanoscale magnetometry, bioimaging, materials characterization, and lab-on-a-chip sensing technologies.
This presentation will give an overview of the NV center’s optical properties, practical design considerations in setting up an ODMR experiment, and the broader role of photonics in quantum sensing.

Kang Xu (CUNY–The City College of New York, United States)

LinkedIn: @Kang Xu‬

Abstract: We use shallow nitrogen-vacancy (NV) centers in diamond to probe the nanoscale dynamics of interfacial water confined between diamond and a fluorinated oil layer. By selectively detecting ¹H and ¹⁹F nuclei using NV-NMR, we resolve distinct diffusion behaviors of water and oil near the interface. Our results reveal that water diffuses much faster than oil and is gradually displaced over days. Molecular dynamics simulations and surface-sensitive X-ray spectroscopy support the observation of slow, thermally driven reorganization. This work highlights NV-NMR as a powerful tool for studying molecular-scale interfacial processes under ambient conditions.