Florian Dolde

Electric-field sensing using single diamond spins.

The ability to sensitively detect charges under amb ient conditions would be a fascinating new tool benefitting a wide range of researchers ac ross disciplines. However, most current techniques are limited to low-temperature methods l ike single-electron transistors (SET)[1,2], single–electron electrostatic force microscopy[3] a nd scanning tunnelling microscopy [4]. Here we open up a new quantum metrology technique demons trating precision electric field measurement using a single nitrogen-vacancy defect entre(NV) spin in diamond. An AC electric field sensitivity reaching ~ 140V/cm/ √Hz has been achieved. This corresponds to the electric field produced by a single elementary char ge located at a distance of ~ 150 nm from our spin sensor with averaging for one second. By caref ul analysis of the electronic structure of the defect centre, we show how an applied magnetic fiel d influences the electric field sensing properties. By this we demonstrate that diamond defct centre spins can be switched between electric and magnetic field sensing modes and ident ify suitable parameter ranges for both detector schemes. By combining magnetic and electri c field sensitivity, nanoscale detection and ambient operation our study opens up new frontiers in imaging and sensing applications ranging from material science to bioimaging.

High-precision nanoscale temperature sensing using single defects in diamond.

Measuring local temperature with a spatial resolution on the order of a few nanometers has a wide range of applications in the semiconductor industry and in material and life sciences. For example, probing temperature on the nanoscale with high precision can potentially be used to detect small, local temperature changes like those caused by chemical reactions or biochemical processes. However, precise nanoscale temperature measurements have not been realized so far owing to the lack of adequate probes. Here we experimentally demonstrate a novel nanoscale temperature sensing technique based on optically detected electron spin resonance in single atomic defects in diamonds. These diamond sensor sizes range from a micrometer down to a few tens of nanometers. We achieve a temperature noise floor of 5 mK/Hz(1/2) for single defects in bulk sensors. Using doped nanodiamonds as sensors the temperature noise floor is 130 mK/Hz(1/2) and accuracies down to 1 mK for nanocrystal sizes and therefore length scales of a few tens of nanometers. This combination of precision and position resolution, combined with the outstanding sensor photostability, should allow the measurement of the heat produced by chemical interactions involving a few or single molecules even in heterogeneous environments like cells.

Room-temperature entanglement between single defect spins in diamond

Entanglement is the central yet fleeting phenomenon of quantum physics. Once being considered a peculiar counter-intuitive property of quantum theory1, it has developed into the most central element of quantum technology. Consequently, there have been a number of experimental demonstrations of entanglement between photons2, atoms3, ions4 and solid-state systems such as spins or quantum dots5, 6, 7, superconducting circuits8, 9 and macroscopic diamond10. Here we experimentally demonstrate entanglement between two engineered single solid-state spin quantum bits (qubits) at ambient conditions. Photon emission of defect pairs reveals ground-state spin correlation. Entanglement (fidelity = 0.67±0.04) is proved by quantum state tomography. Moreover, the lifetime of electron spin entanglement is extended to milliseconds by entanglement swapping to nuclear spins. The experiments mark an important step towards a scalable room-temperature quantum device being of potential use in quantum information processing as well as metrology.

High sensitivity magnetic imaging using an array of spins in diamond.

We present a solid state magnetic field imaging technique using a two-dimensional array of spins in diamond. The magnetic sensing spin array is made of nitrogen vacancy (NV) centers created at shallow depths. Their optical response is used for measuring external magnetic fields in close proximity. Optically detected magnetic resonance is read out from a 60 x 60 microm(2) field of view in a multiplexed manner using a charge coupled device camera. We experimentally demonstrate full two-dimensional vector imaging of the magnetic field produced by a pair of current carrying microwires. The presented wide-field NV magnetometer offers, in addition to its high magnetic sensitivity and vector reconstruction, an unprecedented spatiotemporal resolution and functionality at room temperature.

Dynamical decoupling of a single-electron spin at room temperature

Here we report the increase of the coherence time T

High-fidelity spin entanglement using optimal control

_2

Perfect alignment and preferential orientation of nitrogen-vacancy centers during chemical vapor deposition diamond growth on (111) surfaces

of a single electron spin at room temperature by using dynamical decoupling. We show that the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence can prolong the T

Nanoscale detection of a single fundamental charge in ambient conditions using the NV - Center in diamond

_2

High-resolution correlation spectroscopy of 13C spins near a nitrogen-vacancy centre in diamond

of a single Nitrogen-Vacancy center in diamond up to 2.44 ms compared to the Hahn echo measurement where T

Efficient Photon Collection from a Nitrogen Vacancy Center in a Circular Bullseye Grating

_2 = 390 \mu