Measuring local temperature with a spatial resolution on the order of a few nanometers has a wide range of applications from semiconductor industry over material to life sciences [1]. When combined with precision temperature measurement it promises to give excess to small temperature changes caused e.g. by chemical reactions or biochemical processes [2]. However, nanoscale temperature measurements and precision have excluded each other so far owing to the physical processes used for temperature measurement of limited stability of nanoscale probes [3]. Here we experimentally demonstrate a novel nanoscale temperature sensing technique based on single atomic defects in diamonds. Sensor sizes range from millimeter down to a few tens of nanometers. Utilizing the sensitivity of the optically accessible electron spin level structure to temperature changes [4] we achieve a temperature noise floor of 5 mK/ √ Hz for single defects in bulk sensors. Using doped nanodiamonds as sensors yields temperature measurement with 130 mK/ √ Hz noise floor and accuracies down to 1 mK at length scales of a few ten nanometers. The high sensitivity to temperature changes together with excellent spatial resolution combined with outstanding sensor stability allows for nanoscale precision temperature determination enough to measure chemical processes of few or single molecules by their reaction heat even in heterogeneous environments like cells.Several kinds of nanoscale temperature sensing techniques have been developed in the recent past [1]. These are scanning thermal microscopes (SThM) [5], dispersed or scanned individual nanoprobes [3,6], direct methods like micro-Raman spectroscopy [7] or near-field optical temperature measurements [8]. SThMs have temperature sensitive elements at a scanning tip (e.g. thermocouple), the nanoprobes have temperature dependent properties (e.g. fluorescence spectrum) which can be accessed without direct contact.In this study utilize a single quantum system in a solid state matrix as a temperature nanoprobe, namely the negatively charged nitrogen-vacancy (NV) center in diamond, which allows probe sizes down to ∼ 5 nm [9]. High fidelity control of its ground state electronic and nuclear spins has been demonstrated for various quantum information test experiments [10-15] as well as for nanometer scale metrology purposes [16][17][18][19] e.g. measuring small magnetic and electric fields. Here we show that it also allows tracking temperature with high precision. Temperature nanoprobes can be either dispersed in the specimen to be investigated or used in scanning probe geometry (see fig. 1a).The NV center is a molecular impurity in diamond comprising a substitutional nitrogen impurity and an adjacent carbon vacancy. Optical excitation in a wavelength range from 460 nm to 580 nm yields intense fluorescence emission [20]. Excitation also leads to a high degree of ground state electron spin polarization (S = 1, the actual sensor level) into its m S = 0 (|0 ) sublevel [21]. Furthermore the fluorescence decreases upo...

The detection of single nuclear spins would be useful for fields ranging from basic science to quantum information technology. However, although sensing based on diamond defects and other methods have shown high sensitivity, they have not been capable of detecting single nuclear spins, and defect-based techniques further require strong defect-spin coupling. Here, we present the detection and identification of single and remote (13)C nuclear spins embedded in nuclear spin baths surrounding a single electron spin of a nitrogen-vacancy centre in diamond. We are able to amplify and detect the weak magnetic field noise (∼10 nT) from a single nuclear spin located ∼3 nm from the centre using dynamical decoupling control, and achieve a detectable hyperfine coupling strength as weak as ∼300 Hz. We also confirm the quantum nature of the coupling, and measure the spin-defect distance and the vector components of the nuclear field. The technique marks a step towards imaging, detecting and controlling nuclear spins in single molecules.

Spins of negatively charged nitrogen-vacancy (NV − ) defects in diamond are among the most promising candidates for solid-state qubits. The fabrication of quantum devices containing these spin-carrying defects requires position-controlled introduction of NV − defects having excellent properties such as spectral stability, long spin coherence time, and stable negative charge state. Nitrogen ion implantation and annealing enable the positioning of NV − spin qubits with high precision, but to date, the coherence times of qubits produced this way are short, presumably because of the presence of residual radiation damage. In the present work, we demonstrate that a high temperature annealing at 1000• C allows 2 millisecond coherence times to be achieved at room temperature. These results were obtained for implantation-produced NV − defects in a high-purity, 99.99% 12 C enriched single crystal chemical vapor deposited diamond. We discuss these remarkably long coherence times in the context of the thermal behavior of residual defect spins. [Published in Physical Review B 88, 075206 (2013)]

Nitrogen impurities help to stabilize the negatively-charged-state of NV − in diamond, whereas magnetic fluctuations from nitrogen spins lead to decoherence of NV − qubits. It is not known what donor concentration optimizes these conflicting requirements. Here we used 10 MeV 15 N 3+ ion implantation to create NV − in ultrapure diamond. Optically detected magnetic resonance of single centers revealed a high creation yield of 40 ± 3% from 15 N 3+ ions and an additional yield of 56 ± 3% from 14 N impurities. High-temperature anneal was used to reduce residual defects, and charge stable NV − , even in a dilute 14 N impurity concentration of 0.06 ppb were created with long coherence times.The realization of quantum registers, which are comprised of several quantum bits (qubits), is currently a central issue in quantum information and computation science.1 Among many competing quantum systems, photoactive defect spins of negatively charged nitrogen vacancy (NV − ) centers in diamond are unique solid-state qubits, due in part to ambient pressure and temperature operation.2-4 The NV − center is a single-photon emitter with zero-phonon-line (ZPL) at 637 nm, 5 where both of 3 A 2 electronic ground and 3 E excited states locate inside the diamond band-gap. The spin sublevels, |m s = 0 and |m s = ±1 , of the triplet (S = 1) ground state are separated by ∼ 2.87 GHz due to spin-spin interaction.6 Arbitrary states including superpositions of spin levels may be created by resonant microwave pulses after optical initialization, and then readout by measuring fluorescence intensity.3 Experimental proofs of strongly-coupled NV − spins, 7-9 magnetic coupling between a NV − spin and another electron spin 9,10 or nuclear spins, 11-15 , in addition to coupling to photons 16,17 or optical cavities, 18-20 exemplify the robust yet mutable nature of the NV scheme as well as the beginnings of scalability.The NV quantum coherence decays in time due to magnetic fluctuations from substitutional nitrogen (N 0 s ) electron spins and 13 C nuclear spins, and spin-lattice relaxation.21-23 Thus, the use of high purity ([N 0 s ] ∼ ppb) type IIa diamonds with reduced 13 C content, and position controlled N ion implantation to create NV − centers, is a promising avenue towards a high quality multiqubit system.8 Nevertheless, substitutional nitrogen impurities, which donate electrons to NV centers, are actually essential for stabilizing the NV − charge state. 24The negative NV charge state is predominant at thermal 26 The presence of the neutral NV 0 charge state (S = 1/2) is undesirable as its applications are hindered by rapid dephasing in the ground state. Therefore, the understanding of a minimum concentration threshold of N 0 s impurities in order to form stable NV − spin qubits is of concern for reliable engineering and scalability.In this study we isotopically distinguish engineered 15 NV − spin qubits due to 15 N implantation from 14 NV − due to preexisting 14 N impurities in ultrapure diamond, both of which can be created by 15 N 3+ (10 MeV) im...