Paola Cappellaro

Nanoscale magnetic sensing with an individual electronic spin in diamond

Detection of weak magnetic fields with nanoscale spatial resolution is an outstanding problem in the biological and physical sciences. For example, at a distance of 10 nm, the spin of a single electron produces a magnetic field of about 1 μT, and the corresponding field from a single proton is a few nanoteslas. A sensor able to detect such magnetic fields with nanometre spatial resolution would enable powerful applications, ranging from the detection of magnetic resonance signals from individual electron or nuclear spins in complex biological molecules to readout of classical or quantum bits of information encoded in an electron or nuclear spin memory. Here we experimentally demonstrate an approach to such nanoscale magnetic sensing, using coherent manipulation of an individual electronic spin qubit associated with a nitrogen-vacancy impurity in diamond at room temperature. Using an ultra-pure diamond sample, we achieve detection of 3 nT magnetic fields at kilohertz frequencies after 100 s of averaging. In addition, we demonstrate a sensitivity of 0.5 μT Hz-1/2 for a diamond nanocrystal with a diameter of 30 nm.

Magnetic field imaging with nitrogen-vacancy ensembles

We demonstrate a method of imaging spatially varying magnetic fields using a thin layer of nitrogen-vacancy (NV) centers at the surface of a diamond chip. Fluorescence emitted by the two-dimensional NV ensemble is detected by a CCD array, from which a vector magnetic field pattern is reconstructed. As a demonstration, ac current is passed through wires placed on the diamond chip surface, and the resulting ac magnetic field patterns are imaged using an echo-based technique with sub-micron resolution over a 140µm◊140µm field of view, giving single-pixel sensitivity 100nT/ p Hz. We discuss ongoing efforts to further improve the sensitivity, as well as potential bioimaging applications such as real-time imaging of activity in functional, cultured networks of neurons.

Strong magnetic coupling between an electronic spin qubit and a mechanical resonator

We describe a technique that enables a strong coherent coupling between a single electronic spin qubit associated with a nitrogen-vacancy impurity in diamond and the quantized motion of a magnetized nanomechanical resonator tip. This coupling is achieved via careful preparation of dressed spin states which are highly sensitive to the motion of the resonator but insensitive to perturbations from the nuclear-spin bath. In combination with optical pumping techniques, the coherent exchange between spin and motional excitations enables ground-state cooling and controlled generation of arbitrary quantum superpositions of resonator states. Optical spin readout techniques provide a general measurement toolbox for the resonator with quantum limited precision.

Coherence of Nitrogen-Vacancy Electronic Spin Ensembles in Diamond

We present an experimental and theoretical study of electronic spin decoherence in ensembles of nitrogen-vacancy (NV) color centers in bulk high-purity diamond at room temperature. Under appropriate conditions, we find ensemble NV spin coherence times

Suppression of spin-bath dynamics for improved coherence of multi-spin-qubit systems

({T}_{2})

Time-resolved magnetic sensing with electronic spins in diamond

comparable to that of single NV with

Coherence and Control of Quantum Registers Based on Electronic Spin in a Nuclear Spin Bath

{T}_{2}g600\text{ }\ensuremath{\mu}\text{s}

Coherence of an optically illuminated single nuclear spin qubit.

for a sample with natural abundance of

Entanglement assisted metrology.

^{13}\text{C}

Simulations of Information Transport in Spin Chains

and paramagnetic impurity density