Microscopic Imaging of the Stress Tensor in Diamond Using in Situ Quantum Sensors.

The precise measurement of mechanical stress at the nanoscale is of fundamental and technological importance. In principle, all six independent variables of the stress tensor, which describe the direction and magnitude of compression/tension and shear stress in a solid, can be exploited to tune or enhance the properties of materials and devices. However, existing techniques to probe the local stress are generally incapable of measuring the entire stress tensor. Here, we make use of an ensemble of atomic-sized in situ strain sensors in diamond (nitrogen-vacancy defects) to achieve spatial mapping of the full stress tensor, with a submicrometer spatial resolution and a sensitivity of the order of 1 MPa (10 MPa) for the shear (axial) stress components. To illustrate the effectiveness and versatility of the technique, we apply it to a broad range of experimental situations, including mapping the stress induced by localized implantation damage, nanoindents, and scratches. In addition, we observe surprisingly large stress contributions from functional electronic devices fabricated on the diamond and also demonstrate sensitivity to deformations of materials in contact with the diamond. Our technique could enable in situ measurements of the mechanical response of diamond nanostructures under various stimuli, with potential applications in strain engineering for diamond-based quantum technologies and in nanomechanical sensing for on-chip mass spectroscopy.

Indistinguishable photons from separated silicon-vacancy centers in diamond.

We demonstrate that silicon-vacancy (SiV) centers in diamond can be used to efficiently generate coherent optical photons with excellent spectral properties. We show that these features are due to the inversion symmetry associated with SiV centers. The generation of indistinguishable single photons from separated emitters at 5 K is demonstrated in a Hong-Ou-Mandel interference experiment. Prospects for realizing efficient quantum network nodes using SiV centers are discussed.

Multiple intrinsically identical single-photon emitters in the solid state.

Emitters of indistinguishable single photons are crucial for the growing field of quantum technologies. To realize scalability and increase the complexity of quantum optics technologies, multiple independent yet identical single-photon emitters are required. However, typical solid-state single-photon sources are inherently dissimilar, necessitating the use of electrical feedback or optical cavities to improve spectral overlap between distinct emitters. Here we demonstrate bright silicon vacancy (SiV(-)) centres in low-strain bulk diamond, which show spectral overlap of up to 91% and nearly transform-limited excitation linewidths. This is the first time that distinct single-photon emitters in the solid state have shown intrinsically identical spectral properties. Our results have impact on the application of single-photon sources for quantum optics and cryptography.

Detecting and polarizing nuclear spins with double resonance on a single electron spin.

We report the detection and polarization of nuclear spins in diamond at room temperature by using a single nitrogen-vacancy (NV) center. We use Hartmann-Hahn double resonance to coherently enhance the signal from a single nuclear spin while decoupling from the noisy spin bath, which otherwise limits the detection sensitivity. As a proof of principle, we (i) observe coherent oscillations between the NV center and a weakly coupled nuclear spin and (ii) demonstrate nuclear-bath cooling, which prolongs the coherence time of the NV sensor by more than a factor of 5. Our results provide a route to nanometer scale magnetic resonance imaging and novel quantum information processing protocols.

Experimental implementation of assisted quantum adiabatic passage in a single spin.

Quantum adiabatic passages can be greatly accelerated by a suitable control field, called a counter-diabatic field, which varies during the scan through resonance. Here, we implement this technique on the electron spin of a single nitrogen-vacancy center in diamond. We demonstrate two versions of this scheme. The first follows closely the procedure originally proposed by Demirplak and Rice [J. Phys. Chem. A 107, 9937 (2003)]. In the second scheme, we use a control field whose amplitude is constant but whose phase varies with time. This version, which we call the rapid-scan approach, allows an even faster passage through resonance and therefore makes it applicable also for systems with shorter decoherence times.

Structure activity relationships of synthetic antibiotic analogues of chryscandin.

Anti-yeast activity with a series of chryscandin derivatives showed that the O-methyl-L-tyrosyl moiety is not always required for activity at the target site. On the other hand, the adenyl-3'-aminoribofuranuronic acid moiety seems to be essential for biological activity. Therefore, the various acyl derivatives on the amino group of the sugar part of the nucleoside were synthesized. 1-(6-Amino-9H-purin-9-yl)-3-(S-benzyl-L-cysteinylamino)- 1,3-dideoxy-beta-D-ribofuranuronic acid (16) showed the highest efficacy among them against Candida albicans. It exhibited sixteen-fold enhanced activity in vitro compared with that of native chryscandin. The in vivo activity of 16 against experimental infection of C. albicans showed the almost same as that of 5-fluorocytosine and a superior to that of ketoconazole.

Chryscandin, a novel peptidyl nucleoside antibiotic. II. Structure determination and synthesis.

The structure of chryscandin, a novel antifungal antibiotic, produced by Chrysosporium pannorum No. 4629 was deduced to be 1 from spectroscopic and chemical evidences. In order to confirm the structure and to determine the absolute configuration, the total synthesis of chryscandin was performed. D-Xylose was transformed into 10 in ten steps. After beta-glycosidation of silylated benzoyl adenine with 10, the resulting 11 was converted into 4, which was identical with the product obtained from chryscandin by alkaline hydrolysis. From the key intermediate 13, chryscandin was synthesized via peptide formation followed by removal of the protecting groups. Chryscandin (1) is the first naturally occurring nucleoside antibiotic possessing a 3-aminoribofuranuronic acid in the molecule.

Studies of 7 beta-[2-(aminoaryl)acetamido]-cephalosporin derivatives. I. Synthesis and structure-activity relationships in the aminopyridine series.

The synthesis and in vitro activity of 7 beta-(2-aminopyridyl-2-alkoxyiminoacetamido)cephalosporins with various substituents at the 3-position are described. The effects of substitution pattern on the pyridine ring, oxime substituent and 3-substituent were studied as a function of the MIC values. Of these various kinds of derivatives, 7 beta-[2-(2-aminopyridin-6-yl)-2-alkoxyiminoacetamido]cephalo sporins exhibited significantly higher activity against most of micro-organisms.

Studies of 7 beta-[2-(aminoaryl)acetamido]-cephalosporin derivatives. II. Synthesis and structure-activity relationships in the aminopyrimidine series.

The synthesis and the antibacterial activity of 7 beta-[2-(aminopyrimidinyl)-2-oxyiminoacetamido]cephalosporin s with various substituents at the 3-position in the cephem nucleus are described. The 7 beta-[2-(4-aminopyrimidin-2-yl)-2 -methoxyiminoacetamido]cephalosporin derivative (1) showed significantly higher activity than the corresponding 2-aminopyrimidin-4-yl derivative (2) against Gram-negative bacteria. It was also higher in potency against Escherichia coli and Serratia marcescens than the aminopyridyl compound (4).

Studies of 7 beta-[2-(aminoaryl)acetamido]-cephalosporin derivatives. III. Synthesis and structure-activity relationships in the aminothiadiazole series.

The synthesis and in vitro antibacterial activity of 7 beta-[2-(5-amino-1,2,4-thiadiazol-3-yl)-2-oxyiminoacetamido] cephalosporins with various substituents at the 3-position in the cephem nucleus are described. Aminothiadiazolyl cephalosporins having pyridiniomethyl groups at the 3-position exhibited excellent activity against all organisms, particularly against Pseudomonas aeruginosa.