• Session Info

Nanoscale covariance magnetometry with diamond quantum sensors
Correlated phenomena play a central role in condensed matter physics, but in many cases there are no tools available that allow for measurements of correlations at the relevant length scales (nanometers - microns). We have recently demonstrated that nitrogen vacancy (NV) centers in diamond can be used as point sensors for measuring two-point magnetic field correlators [1]. NV centers are atom-scale defects that can be used to sense magnetic fields with high sensitivity and spatial resolution. Typically, the magnetic field is measured by averaging sequential measurements of single NV centers, or by spatial averaging over ensembles of many NV centers, which provides mean values that contain no nonlocal information about the relationship between two points separated in space or time. We recently proposed and implemented a sensing modality whereby two or more NV centers are measured simultaneously, from which we extract temporal and spatial correlations in their signals that would otherwise be inaccessible. We demonstrate measurements of correlated applied noise using spin-to-charge readout of two NV centers and implement a spectral reconstruction protocol for disentangling local and nonlocal noise sources. This novel quantum sensing platform will allow us to measure new physical quantities that are otherwise inaccessible with current tools, particularly in condensed matter systems where two-point correlators can be used to characterize charge transport, magnetism, and non-equilibrium dynamics.

[1] "Nanoscale covariance magnetometry with diamond quantum sensors," J. Rovny, Z. Yuan, M. Fitzpatrick, A. I. Abdalla, L. Futamura, C. Fox, M. C. Cambria, S. Kolkowitz, N. P. de Leon, Science 378, 6626 1301-1305 (2022).

• Session Info

Quantum Sensing of Two-Dimensional Magnetism

References:

1. N. J. McLaughlin et al., Nano Lett. 22, 5810 (2022).
2. M. Huang et al., Nano Lett. 23, 8099 (2023).
3. M. Huang et al., Nat. Commun. 14, 5259 (2023).
4. M. Huang et al., Nat. Commun. 13, 5369 (2022).

• Session Info

Charge and spin noise for spin-1 qubits in diamond and silicon carbide

I will describe some general theoretical features of charge and spin noise on coherent spin-1 centers embedded in wide bandgap hosts (e.g. diamond and silicon carbide), including effects on optical linewidths[1] and spin coherence times[2,3]. We see that the spin coherence times of sensing qubits may be able to quantitatively identify the diffusive motion of nearby charge carriers through an analysis of the spatio-temporal correlations of the noise[2]. We find unusual effects of electric/charge noise, often producing effects that in simpler models are assigned to magnetic noise alone[3].  Similar simulations permit us to identify the effect of coating diamond nanoparticles, which lengthen the coherence times of NV- spin centers to near bulk values[4]. In media that provide highly coherent magnetic excitations (magnons) these magnons may be of use for qubit entangling gates[5]; recent measurements have identified the back-action of these excitations on the coherence times of a single qubit[6]. Work supported by DOE BES.

[1] PRXQ 2, 040310 (2021)

[2] arXiv:2112.15581

[3] arXiv:2303.13370

[4] arXiv:2305.03075

[5] PRXQ 2, 040314 (2021)

[6] PNAS 121, e2313754120 (2024).

• Session Info

Quantum metrology enables some of the world's most sensitive measurements. When applied to biophysical systems, diamond-based quantum sensors have the potential to probe processes that cannot be accessed by conventional technologies. Examples of such processes range from cancer research to neuroscience to developmental biology. However, interfacing coherent qubit sensors with fragile biological target systems has remained an outstanding challenge that has severely limited applications. In this talk, I will discuss a novel approach that combines single-molecule biophysics technology with quantum engineering to interface intact biomolecules on a diamond quantum sensor without impacting qubit coherence and bio-functionality. In a second part, I will discuss our recent work on engineering highly coherent quantum sensors based on diamond nanocrystal. Such nanosensors can readily be taken up by cells and integrated into intact organisms. However, coherence in these nanocrystal sensors is limited by surface noise, which severely reduces the sensor’s sensitivity. In our work we developed a new approach to engineer spin coherence in core-shell nanostructures which leads to a 50-fold improvement in qubit sensitivity. Finally, potential future applications of quantum sensing to biophysics and diagnostics will be discussed.

• Session Info

Characterization and control of sub-diffraction color centers clusters in diamond

Under cryogenic conditions, color centers in wide-bandgap semiconductors feature a collection of "atomic-like" absorption resonances that can be exploited to examine and control their charge states in novel ways. In the first part of this talk, I will discuss how the local heterogeneity of these resonances can be leveraged to individually manipulate and readout the charge state of nitrogen-vacancy (NV) centers in diamond sharing the same diffraction-limited volume. I will also examine how to capitalize on the spectral diffusion of individual NVs in sub-diffraction clusters to establish statistical correlations between the temporal frequency shifts in each of the spectra, and ultimately map out proximal trapped charge in three dimensions. All in all, these results open intriguing opportunities for information processing in the form of devices with enhanced optical storage capacity and for the manipulation of nanoscale spin-qubit clusters connected via electric and/or magnetic couplings.

• Session Info

Studying and multiplexing nitrogen-vacancy centers in diamond

The nitrogen-vacancy (NV) center in diamond has been widely adopted as a quantum sensor, and is now even used in undergraduate instructional labs as a model quantum system. However, despite its ubiquity and popularity, basic properties of the NV center remain poorly understood. In addition, most work has been restricted to measurements of one NV center at a time, or to globally averaged measurements of ensembles of many of NV centers. In this talk I will first present a recent experimental and theoretical study of temperature and spin-state-dependent spin-phonon relaxation rates in the electronic ground state spin-triplet of NV centers in diamond, and will discuss how these new insights could lead to magnetometers with enhanced sensitivity. I will also explain how these results led us to a simple, analytical, physically motivated expression for the temperature dependence of the zero-field splitting of the NV center electronic ground state, with applications to nanoscale thermometry. I will then briefly present our experimental demonstration of spatiotemporal magnetic field correlation measurements with pairs of NV centers, including the ability to distinguish between global and local noise sources, and the capability to measure signals of interest using free precession times beyond the apparent single NV coherence time in certain regimes. Finally, I will present on a new experimental platform we have developed for simultaneously manipulating and independently measuring many single NV centers in parallel.