Fast Room-Temperature Phase Gate on a Single Nuclear Spin in Diamond

Nuclear spins support long lived quantum coherence due to weak coupling to the environment, but are difficult to rapidly control using nuclear magnetic resonance (NMR) as a result of the small nuclear magnetic moment. We demonstrate a fast ~ 500 ns nuclear spin phase gate on a 14N nuclear spin qubit intrinsic to a nitrogen-vacancy (NV) center in diamond. The phase gate is enabled by the hyperfine interaction and off-resonance driving of electron spin transitions. Repeated applications of the phase gate bang-bang decouple the nuclear spin from the environment, locking the spin state for up to ~ 140 microseconds.Comment: Related papers at http://pettagroup.princeton.ed

Highly-tunable formation of nitrogen-vacancy centers via ion implantation

We demonstrate highly-tunable formation of nitrogen-vacancy (NV) centers using 20 keV 15N+ ion implantation through arrays of high-resolution apertures fabricated with electron beam lithography. By varying the aperture diameters from 80 to 240 nm, as well as the average ion fluences from 5 x 10^10 to 2 x 10^11 ions/cm^2, we can control the number of ions per aperture. We analyze the photoluminescence on multiple sites with different implantation parameters and obtain ion-to-NV conversion yields of 6 to 7%, consistent across all ion fluences. The implanted NV centers have spin dephasing times T2* ~ 3 microseconds, comparable to naturally occurring NV centers in high purity diamond with natural abundance 13C. With this technique, we can deterministically control the population distribution of NV centers in each aperture, allowing for the study of single or coupled NV centers and their integration into photonic structures.Comment: Related papers at http://pettagroup.princeton.ed

Charge State Dynamics and Optically Detected Electron Spin Resonance Contrast of Shallow Nitrogen-Vacancy Centers in Diamond

Nitrogen-vacancy (NV) centers in diamond can be used for nanoscale sensing with atomic resolution and sensitivity; however, it has been observed that their properties degrade as they approach the diamond surface. Here we report that in addition to degraded spin coherence, NV centers within nanometers of the surface can also exhibit decreased fluorescence contrast for optically detected electron spin resonance (OD-ESR). We demonstrate that this decreased OD-ESR contrast arises from charge state dynamics of the NV center, and that it is strongly surface-dependent, indicating that surface engineering will be critical for nanoscale sensing applications based on color centers in diamond

Diamond Surface Functionalization via Visible Light-Driven C-H Activation for Nanoscale Quantum Sensing

Nitrogen-vacancy centers in diamond are a promising platform for nanoscale nuclear magnetic resonance sensing. Despite significant progress towards using NV centers to detect and localize nuclear spins down to the single spin level, NV-based spectroscopy of individual, intact, arbitrary target molecules remains elusive. NV molecular sensing requires that target molecules are immobilized within a few nanometers of NV centers with long spin coherence time. The inert nature of diamond typically requires harsh functionalization techniques such as thermal annealing or plasma processing, limiting the scope of functional groups that can be attached to the surface. Solution-phase chemical methods can be more readily generalized to install diverse functional groups, but they have not been widely explored for single-crystal diamond surfaces. Moreover, realizing shallow NV centers with long spin coherence times requires highly ordered single-crystal surfaces, and solution-phase functionalization has not yet been shown to be compatible with such demanding conditions. In this work, we report a versatile strategy to directly functionalize C-H bonds on single-crystal diamond surfaces under ambient conditions using visible light. This functionalization method is compatible with charge stable NV centers within 10 nm of the surface with spin coherence times comparable to the state of the art. As a proof of principle, we use shallow ensembles of NV centers to detect nuclear spins from functional groups attached to the surface. Our approach to surface functionalization based on visible light-driven C-H bond activation opens the door to deploying NV centers as a broad tool for chemical sensing and single-molecule spectroscopy

Origins of Diamond Surface Noise Probed by Correlating Single-Spin Measurements with Surface Spectroscopy

The nitrogen vacancy (NV) center in diamond exhibits spin-dependent fluorescence and long spin coherence times under ambient conditions, enabling applications in quantum information processing and sensing. NV centers near the surface can have strong interactions with external materials and spins, enabling new forms of nanoscale spectroscopy. However, NV spin coherence degrades within 100 nanometers of the surface, suggesting that diamond surfaces are plagued with ubiquitous defects. Prior work on characterizing near-surface noise has primarily relied on using NV centers themselves as probes; while this has the advantage of exquisite sensitivity, it provides only indirect information about the origin of the noise. Here we demonstrate that surface spectroscopy methods and single spin measurements can be used as complementary diagnostics to understand sources of noise. We find that surface morphology is crucial for realizing reproducible chemical termination, and use these insights to achieve a highly ordered, oxygen-terminated surface with suppressed noise. We observe NV centers within 10 nm of the surface with coherence times extended by an order of magnitude

Quantum Control of Nuclear Spins Coupled to Nitrogen-Vacancy Centers in Diamond

This dissertation presents experiments on nitrogen-vacancy (NV) defect centers in diamond. The NV center is an optically active color center formed by one substitutional nitrogen atom and an adjacent vacancy in the diamond lattice. Its ground state spin triplet transitions are accessible in the microwave regime and their corresponding excited state transitions exhibit spin-dependent fluorescence that allows for optical spin state readout. We present methods for the deterministic placement and the fine tuning of the NV center population in bulk diamond via ion implantation. We demonstrate quantum control of the nuclear spin in diamond through manipulation of the NV center electronic spin. By utilizing the hyperfine coupling between the electronic and nuclear spins, fast phase gates on the intrinsic nitrogen nuclear spin can be achieved within half a microsecond, a speed that far exceeds that of the gates performed with conventional nuclear magnetic resonance pulses. The hyperfine coupling also results in an enhancement of the effective nuclear gyromagnetic ratio. We demonstrate the tunability of this enhancement by changing the magnetic field. Finally, we discuss preliminary experiments aimed towards coupling a single NV center to higher nuclear spin systems

Gamma-induced interconnected networks in microporous activated carbons from palm petiole under NaNO3 oxidizing environment towards high-performance electric double layer capacitors (EDLCs)

Abstract Activated carbons (ACs) were developed from palm petiole via a new eco-friendly method composed of highly diluted H2SO4 hydrothermal carbonization and low-concentration KOH-activating pyrolysis followed by gamma-induced surface modification under NaNO3 oxidizing environment. The prepared graphitic carbons were subsequently used as an active material for supercapacitor electrodes. The physiochemical properties of the ACs were characterized using field emission scanning electron microscope–energy dispersive X-ray spectroscopy, N2 adsorption/desorption isotherms with Brunauer–Emmett–Teller surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of the fabricated electrodes was investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Even treated with extremely low H2SO4 concentration and small KOH:hydrochar ratio, the maximum SBET of 1365 m2 g−1 for an AC was obtained after gamma irradiation. This was attributed to radiation-induced interconnected network formation generating micropores within the material structure. The supercapacitor electrodes exhibited electric double-layer capacitance giving the highest specific capacitance of 309 F g−1 as well as excellent cycle stability within 10,000 cycles. The promising results strongly ensure high possibility of the eco-friendly method application in supercapacitor material production

Effect on Vitamin D status of Breastfeeding Infants after Vitamin D3 Supplementation during Breastfeeding Lactation: A double-blind randomized controlled trial

Background: Vitamin D deficiency in pregnancy increases several risks of breastfed mothers. To prevent these adverse events, vitamin D supplementation during pregnancy and lactation is recommended, but suggested dose ranges vary. Objective: To determine whether vitamin D3 1,800 IU/d supplementation in lactating mothers improves the vitamin D status of their breastfed infants. Materials and Methods: A randomized, placebo–controlled trial with Thai pregnant women was conducted. Lactating mothers (n=72) and their breastfed infants with insufficient maternal 25 hydroxyvitamin D (25(OH)D) levels in the third trimester were randomly assigned to two groups, one of which received 1,800 IU/d vitamin D supplementation and the other a placebo. Maternal serum 25(OH)D during lactation, cord blood, and 6-week breastfed infant serum were measured using LC-MS/MS. Results: Mean maternal age (±SD) was 27±5 years, and pre-gestational BMI was 22.29±5 kg/m2. Maternal serum 25(OH)D at baseline was 22.29±7.15 nmol/L. At 6 weeks, both maternal 25(OH)D and infant 25 (OH)D levels had increased significantly in the vitamin D supplement group of mothers and infants (68.30±15.40, 40.40±12.56 nmol/L) compared to those in placebo groups (55.15±13.57, 24.28±17.20 nmol/L) (p <0.001, p<0.001). The changes in infant 25(OH)D levels increased substantially in the vitamin D supplement group but decreased in placebo(17.49±16.27 ng/ml compared to -1.34±19.23 nmol/L in the placebo group, p<0.001). The change of maternal 25(OH)D were positively correlation to the change of 25(OH)D level in breastmilk mothers and infants by r=0.697, p<0.001 and r=0.379, p=0.003 respectively. Conclusions: Vitamin D3 supplementation to breastfed mother during lactation can increase serum 25(OH)D level in Thai breastfed mother and infants. Further work is needed to determine the optimum duration of vitamin D supplementation to normalized breastfed infants with 25(OH)D level >75 nmol/L