arXiv subjects

Kai-Hung Cheng

Publications and source records attributed to Kai-Hung Cheng.

3 recordsLinked to original sources

arXiv2026

Momentum-resolved quantum noise spectroscopy using ensembles of diamond quantum sensors

Spatiotemporal fluctuations across multiple scales govern and characterize the emergent properties, phase boundaries, and low-energy excitations of strongly correlated matter. However, capturing these dynamics has remained a major experimental challenge, as conventional probes typically offer either high spatial or temporal resolution, but not both simultaneously. Here, we leverage high-fidelity wide-field imaging of dense diamond nitrogen vacancy center ensembles to measure the momentum and frequency power spectral density of magnetic fluctuations. To access spatial wavevectors below the diffraction limit, we tune the sensing volume continuously through optical depletion. This approach enables study of equilibrium and driven fluctuations across three orders of magnitude in spatial scale and tunable frequency bands, providing a direct means to map low-energy, long-wavelength fluctuations in correlated systems.

quant-ph↗

arXiv2025

High-quality nanostructured diamond membranes for nanoscale quantum sensing

Deploying nitrogen vacancy (NV) centers in diamond as nanoscale quantum sensors for condensed matter and materials physics requires placing the NV centers close to the sensing target. One solution is to fabricate diamond nanostructures and integrate them with materials and devices. However, diamond etching and ion milling can introduce subsurface damage and surface defects that degrade the charge stability and spin coherence of NV centers near the surface. Here we report a procedure for fabricating low-damage nanostructured diamond membranes, and we show that this fabrication scheme preserves the optical and spin properties of state-of-the-art shallow NV center quantum sensors, within nanometers of the diamond surface, while providing significant photonic enhancement. Furthermore, we demonstrate a pick-and-place transfer method, which enables integration with diverse sensing targets.

cond-mat.mes-hall↗

arXiv2024

Massively multiplexed nanoscale magnetometry with diamond quantum sensors

Single nitrogen vacancy (NV) centers in diamond have been used extensively for high-sensitivity nanoscale sensing, but conventional approaches use confocal microscopy to measure individual centers sequentially, limiting throughput and access to non-local physical properties. Here we design and implement a multiplexed NV sensing platform that allows us to read out many single NV centers simultaneously using a low-noise camera. Using this platform, we coherently manipulate and read out the spin states of hundreds of individual NV centers in parallel, achieving comparable magnetic field sensitivity to confocal measurements. We also implement a parallelized version of spin-to-charge-conversion readout for low NV center spin state readout noise and use it to demonstrate multiplexed covariance magnetometry, in which we measure six two-point magnetic field correlators from four NV centers simultaneously. The number of correlators we can measure is limited only by the available laser power, opening the door to massively multiplexed covariance magnetometry. Our platform significantly increases the throughput and broadens the applications of nanoscale sensing using diamond quantum sensors.

quant-ph↗