Nuclear magnetic resonance spectroscopy is a powerful tool for the structural analysis of organic compounds and biomolecules but typically requires macroscopic sample quantities. We use a sensor, which consists of two quantum bits corresponding to an electronic spin and an ancillary nuclear spin, to demonstrate room temperature magnetic resonance detection and spectroscopy of multiple nuclear species within individual ubiquitin proteins attached to the diamond surface. Using quantum logic to improve readout fidelity and a surface-treatment technique to extend the spin coherence time of shallow nitrogen-vacancy centers, we demonstrate magnetic field sensitivity sufficient to detect individual proton spins within 1 second of integration. This gain in sensitivity enables high-confidence detection of individual proteins and allows us to observe spectral features that reveal information about their chemical composition.

We demonstrate a robust experimental method for determining the depth of individual shallow Nitrogen-Vacancy (NV) centers in diamond with ∼ 1 nm uncertainty. We use a confocal microscope to observe single NV centers and detect the proton nuclear magnetic resonance (NMR) signal produced by objective immersion oil, which has well understood nuclear spin properties, on the diamond surface. We determine the NV center depth by analyzing the NV NMR data using a model that describes the interaction of a single NV center with the statistically-polarized proton spin bath. We repeat this procedure for a large number of individual, shallow NV centers and compare the resulting NV depths to the mean value expected from simulations of the ion implantation process used to create the NV centers, with reasonable agreement.

Two-dimensional (2D) materials offer a promising platform for exploring condensed matter phenomena and developing technological applications. However, the reduction of material dimensions to the atomic scale poses a challenge for traditional measurement and interfacing techniques that typically couple to macroscopic observables. We demonstrate a method for probing the properties of 2D materials via nanometer-scale nuclear quadrupole resonance (NQR) spectroscopy using individual atom-like impurities in diamond. Co-1 herent manipulation of shallow nitrogen-vacancy (NV) color centers enables the probing of nanoscale ensembles down to ∼30 nuclear spins in atomically thin hexagonal boron nitride (h-BN). The characterization of low-dimensional nanoscale materials could enable the development of new quantum hybrid systems, combining atom-like systems coherently coupled with individual atoms in 2D materials. Hexagonal boron nitride (h-BN) is an insulating material consisting of equal concentrations of boron (80%11 B, 20% 10 B) and nitrogen (close to 100% 14 N) in a honeycomb layered structure (1). The individual atomic layers of h-BN are held together by weak van der Waals interactions, allowing the preparation of samples with varying numbers of layers via mechanical exfoliation (2). Nanometer-thick h-BN flakes are being extensively used as dielectric spacers and passivation layers for graphene and transition metal dichalcognides (1, 3). Recent studies have shown that atomically thin h-BN can be the host for interesting quantum defects (4). We investigate both the electron density distribution and spin-spin interactions in nanoscale h-BN volumes by analyzing the magnetic fields produced by 11 B, 10 B and 14 N spins using nanoscale nuclear quadrupole resonance (NQR) spectroscopy (5, 6).Conventional NQR spectroscopy is a powerful tool for chemical analysis that relies on detecting the bulk magnetization of quadrupolar (I > 1/2) nuclear spins in a weak magnetic field (7,8). The NQR spectrum is determined by the interaction between the nuclear electric quadrupole moments and the local electric field gradients (9), and is thus dependent upon the electrostatic environment of the measured spins. In the case when the target material is axially symmetric and no external magnetic field is applied, the quadrupolar interaction defines a principal axis for the nuclear spins. For the special case of I = 3/2, application of a small magnetic field yields a set of perturbed spin 2 eigenstates with energies that depend on the orientation of the applied field with respect to the principal axis (Fig. 1B). NQR spectroscopy yields the transition frequencies and relaxation/decoherence rates, which in turn can be related to various material properties (10, 11) (e.g. chemical composition, bond lengths and angles). However, conventional magnetic resonance methods require macroscopic samples (12) and are not suitable for experiments with atomically thin layers.In our approach, individual NV centers in diamond are used as sensitive, atomicscale ma...

The normal function of Syk in epithelium of the developing or adult breast is not known, however, Syk suppresses tumor growth, invasion, and metastasis in breast cancer cells. Here, we demonstrate that in the mouse mammary gland, loss of one Syk allele profoundly increases proliferation and ductal branching and invasion of epithelial cells through the mammary fat pad during puberty. Mammary carcinomas develop by one year. Syk also suppresses proliferation and invasion in vitro. siRNA or shRNA knockdown of Syk in MCF10A breast epithelial cells dramatically increased proliferation, anchorage independent growth, cellular motility, and invasion, with formation of functional, extracellular matrix-degrading invadopodia. Morphological and gene microarray analysis following Syk knockdown revealed a loss of luminal and differentiated epithelial features with epithelial to mesenchymal transition and a gain in invadopodial cell surface markers CD44, CD49F, and MMP14. These results support the role of Syk in limiting proliferation and invasion of epithelial cells during normal morphogenesis, and emphasize the critical role of Syk as a tumor suppressor for breast cancer. The question of breast cancer risk following systemic anti-Syk therapy is raised since only partial loss of Syk was sufficient to induce mammary carcinomas.

Quantum sensors are finding their way from laboratories to the real world, as witnessed by the increasing number of start-ups in this field. The atomic length scale of quantum sensors and their coherence properties enable unprecedented spatial resolution and sensitivity. Biomedical applications could benefit from these quantum technologies, but it is often difficult to evaluate the potential impact of the techniques. This Review sheds light on these questions, presenting the status of quantum sensing applications and discussing their path towards commercialization. The focus is on two promising quantum sensing platforms: optically pumped atomic magnetometers, and nitrogen–vacancy centres in diamond. The broad spectrum of biomedical applications is highlighted by four case studies ranging from brain imaging to single-cell spectroscopy.