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Register a new userDetection of atomic spin labels in a lipid bi-layer using a single-spin nanodiamond probe
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Magnetic field fluctuations arising from fundamental spins are ubiquitous in nanoscale biology, and are a rich source of information about the processes that generate them. However, the ability to detect the few spins involved without averaging over large ensembles has remained elusive. Here we demonstrate the detection of gadolinium spin labels in an artificial cell membrane under ambient conditions using a single-spin nanodiamond sensor. Changes in the spin relaxation time of the sensor located in the lipid bilayer were optically detected and found to be sensitive to near-individual proximal gadolinium atomic labels. The detection of such small numbers of spins in a model biological setting, with projected detection times of one second, opens a new pathway for in-situ nanoscale detection of dynamical processes in biology.
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Nuclear magnetic resonance (NMR) is a powerful method for determining the structure of molecules and proteins. While conventional NMR requires averaging over large ensembles, recent progress with single-spin quantum sensors has created the prospect of magnetic imaging of individual molecules. As an initial step towards this goal, isolated nuclear spins and spin pairs have been mapped. However, large clusters of interacting spins - such as found in molecules - result in highly complex spectra. Imaging these complex systems is an outstanding challenge due to the required high spectral resolution and efficient spatial reconstruction with sub-angstrom precision. Here we develop such atomic-scale imaging using a single nitrogen-vacancy (NV) centre as a quantum sensor, and demonstrate it on a model system of $27$ coupled $^{13}$C nuclear spins in a diamond. We present a new multidimensional spectroscopy method that isolates individual nuclear-nuclear spin interactions with high spectral resolution ($< 80,$mHz) and high accuracy ($2$ mHz). We show that these interactions encode the composition and inter-connectivity of the cluster, and develop methods to extract the 3D structure of the cluster with sub-angstrom resolution. Our results demonstrate a key capability towards magnetic imaging of individual molecules and other complex spin systems.
We propose a method for detecting the presence of a single spin in a crystal by coupling it to a high-quality factor superconducting planar resonator. By confining the microwave field in a constriction of nanometric dimensions, the coupling constant can be as high as $5-10$,kHz. This coupling affects the amplitude of the field emitted by the resonator, and the integrated homodyne signal allows detection of a single spin with unit signal-to-noise ratio within few milliseconds. We further show that a stochastic master equation approach and a Bayesian analysis of the full time dependent homodyne signal improves this figure by $sim 30%$ for typical parameters.
We experimentally demonstrate a simple and robust protocol for the detection of weak radio-frequency magnetic fields using a single electron spin in diamond. Our method relies on spin locking, where the Rabi frequency of the spin is adjusted to match the MHz signal frequency. In a proof-of-principle experiment we detect a 7.5 MHz magnetic probe field of 40 nT amplitude with <10 kHz spectral resolution over a T_1-limited noise floor of 0.3 nT/rtHz. Rotating-frame magnetometry may provide a direct and sensitive route to high-resolution spectroscopy of nanoscale nuclear spin signals.
The strong driving regime occurs when a quantum two-level system is driven with an external field whose amplitude is greater or equal to the energy splitting between the systems states, and is typically identified with the breaking of the rotating wave approximation (RWA). We report an experimental study, in which the spin of a single nitrogen-vacancy (NV) center in diamond is strongly driven with microwave (MW) fields of arbitrary polarization. We measure the NV center spin dynamics beyond the RWA, and characterize the limitations of this technique for generating high-fidelity quantum gates. Using circularly polarized MW fields, the NV spin can be harmonically driven in its rotating frame regardless of the field amplitude, thus allowing rotations around arbitrary axes. Our approach can effectively remove the RWA limit in quantum-sensing schemes, and assist in increasing the number of operations in QIP protocols.
We use micromagnetic simulation to demonstrate layer-selective detection of magnetization directions from magnetic dots having two recording layers by using a spin-torque oscillator (STO) as a read device. This method is based on ferromagnetic resonance (FMR) excitation of recording-layer magnetizations by the microwave field from the STO. The FMR excitation affects the oscillation of the STO, which is utilized to sense the magnetization states in a recording layer. The recording layers are designed to have different FMR frequencies so that the FMR excitation is selectively induced by tuning the oscillation frequency of the STO. Since all magnetic layers interact with each other through dipolar fields, unnecessary interlayer interferences can occur, which are suppressed by designing magnetic properties of the layers. We move the STO over the magnetic dots, which models a read head moving over recording media, and show that changes in the STO oscillation occur on the one-nanosecond timescale.
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