Transform-Limited Photons From a Coherent Tin-Vacancy Spin in Diamond.

Solid-state quantum emitters that couple coherent optical transitions to long-lived spin qubits are essential for quantum networks. Here we report on the spin and optical properties of individual tin-vacancy (SnV) centers in diamond nanostructures. Through cryogenic magneto-optical and spin spectroscopy, we verify the inversion-symmetric electronic structure of the SnV, identify spin-conserving and spin-flipping transitions, characterize transition linewidths, measure electron spin lifetimes, and evaluate the spin dephasing time. We find that the optical transitions are consistent with the radiative lifetime limit even in nanofabricated structures. The spin lifetime is phonon limited with an exponential temperature scaling leading to T_{1}>10 ms, and the coherence time, T_{2}^{*} reaches the nuclear spin-bath limit upon cooling to 2.9 K. These spin properties exceed those of other inversion-symmetric color centers for which similar values require millikelvin temperatures. With a combination of coherent optical transitions and long spin coherence without dilution refrigeration, the SnV is a promising candidate for feasable and scalable quantum networking applications.

Biosynthesis of silver nanoparticles using Onosma sericeum Willd. and evaluation of their catalytic properties and antibacterial and cytotoxic activity.

In this study, silver nanoparticle (AgNP) synthesis was carried out using Onosma sericeum Willd. aqueous extract for the first time, with a simple, economical, and green method without the need for any other organic solvent or external reducing or stabilizing agent. A variety of AgNPs, all of different particle sizes, were synthesized by controlling the silver ion concentration, extract volume, temperature, and pH. It was determined that the optimum conditions for AgNP synthesis were 1 mM AgNO3, pH 8, 25 °C, 20 g/200 mL extract, silver nitrate, and extract ratio 5:1 (v/v). The AgNPs were defined using UV-Vis spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The particle size distribution and zeta potential measurements of the AgNPs were measured using the dynamic light scattering (DLS) technique. It was determined that the AgNPs with a particle size of less than 10 nm showed a higher catalytic effect in the reduction of 2-nitrobenzenamine. It was also found that these nanoparticles had a cytotoxic effect on the MCF-7 breast cancer cell line depending on dosage and time. The resulting IC50 values were between 76.63 µg/mL and 169.77 µg/mL. Furthermore, the biosynthesized AgNPs showed effective antibacterial activity against the Acinetobacter baumannii bacteria. The results of the study showed that synthesized AgNPs can have a promising role in biomedical and nanobiotechnology applications.

Controlling the coherence of a diamond spin qubit through its strain environment.

The uncontrolled interaction of a quantum system with its environment is detrimental for quantum coherence. For quantum bits in the solid state, decoherence from thermal vibrations of the surrounding lattice can typically only be suppressed by lowering the temperature of operation. Here, we use a nano-electro-mechanical system to mitigate the effect of thermal phonons on a spin qubit - the silicon-vacancy colour centre in diamond - without changing the system temperature. By controlling the strain environment of the colour centre, we tune its electronic levels to probe, control, and eventually suppress the interaction of its spin with the thermal bath. Strain control provides both large tunability of the optical transitions and significantly improved spin coherence. Finally, our findings indicate the possibility to achieve strong coupling between the silicon-vacancy spin and single phonons, which can lead to the realisation of phonon-mediated quantum gates and nonlinear quantum phononics.

All-Optical Control of the Silicon-Vacancy Spin in Diamond at Millikelvin Temperatures.

The silicon-vacancy center in diamond offers attractive opportunities in quantum photonics due to its favorable optical properties and optically addressable electronic spin. Here, we combine both to achieve all-optical coherent control of its spin states. We utilize this method to explore spin dephasing effects in an impurity-rich sample beyond the limit of phonon-induced decoherence: Employing Ramsey and Hahn-echo techniques at temperatures down to 40 mK we identify resonant coupling to a substitutional nitrogen spin bath as limiting decoherence source for the electron spin.

Solid State Spin-Wave Quantum Memory for Time-Bin Qubits.

We demonstrate the first solid-state spin-wave optical quantum memory with on-demand read-out. Using the full atomic frequency comb scheme in a Pr(3+):Y2SiO5 crystal, we store weak coherent pulses at the single-photon level with a signal-to-noise ratio >10. Narrow-band spectral filtering based on spectral hole burning in a second Pr(3+):Y2SiO5 crystal is used to filter out the excess noise created by control pulses to reach an unconditional noise level of (2.0±0.3)×10(-3) photons per pulse. We also report spin-wave storage of photonic time-bin qubits with conditional fidelities higher than achievable by a measure and prepare strategy, demonstrating that the spin-wave memory operates in the quantum regime. This makes our device the first demonstration of a quantum memory for time-bin qubits, with on-demand read-out of the stored quantum information. These results represent an important step for the use of solid-state quantum memories in scalable quantum networks.

1-(4-Fluoro-benz-yl)-2-(pyridin-2-yl)-1H-benzimidazole.

In the title compound, C19H14FN3, the dihedral angles between the benzimidazole unit (r.m.s. deviation= 0.017 Å) and the pyridine and benzene rings are 24.46 (4) and 81.87 (3)°, respectively. In the crystal, mol-ecules are stacked along the a-axis direction by C-H⋯π inter-actions.

Quantum storage of heralded single photons in a praseodymium-doped crystal.

We report on experiments demonstrating the reversible mapping of heralded single photons to long-lived collective optical atomic excitations stored in a Pr3+:Y2SiO5 crystal. A cavity-enhanced spontaneous down-conversion source is employed to produce widely nondegenerate narrow-band (≈2 MHz) photon pairs. The idler photons, whose frequency is compatible with telecommunication optical fibers, are used to herald the creation of the signal photons, compatible with the Pr3+ transition. The signal photons are stored and retrieved using the atomic frequency comb protocol. We demonstrate storage times up to 4.5 µs while preserving nonclassical correlations between the heralding and the retrieved photon. This is more than 20 times longer than in previous realizations in solid state devices, and implemented in a system ideally suited for the extension to spin-wave storage.

Quantum storage of a photonic polarization qubit in a solid.

We report on the quantum storage and retrieval of photonic polarization quantum bits onto and out of a solid state storage device. The qubits are implemented with weak coherent states at the single photon level, and are stored for a predetermined time of 500 ns in a praseodymium doped crystal with a storage and retrieval efficiency of 10%, using the atomic frequency comb scheme. We characterize the storage by using quantum state tomography, and find that the average conditional fidelity of the retrieved qubits exceeds 95% for a mean photon number µ=0.4. This is significantly higher than a classical benchmark, taking into account the poissonian statistics and finite memory efficiency, which proves that our crystal functions as a quantum storage device for polarization qubits. These results extend the storage capabilities of solid state quantum light matter interfaces to polarization encoding, which is widely used in quantum information science.

The effect of cysteine and glutathione on sperm and oxidative stress parameters of post-thawed bull semen.

The aim of this study was to determine the effects of antioxidants such as reduced glutathione (GSH) and cysteine in Laiciphose® extender on semen parameters, fertilizing ability, lipid peroxidation (LPO) level and glutathione peroxidise (GPx) activity of post-thawed bull semen. Totally 54 ejaculates of three bulls were used in the study. Five groups, namely; GSH (0.5 and 2 mM), cysteine (5 and 10 mM) and control group, were conducted to test the antioxidants in Laiciphose®. Insemination doses were processed that each 0.25-mL straw contained 15 x 106 sperm. The addition of antioxidants did not present any significant effect on the percentages of post-thaw sperm morphology (acrosome and total abnormalities), subjective, CASA and progressive motilities, as well as sperm motility characteristics (VAP, VSL, VCL, LIN and ALH), compared to the control groups (P > 0.05). GSH 0.5mM (55.5±7.38%) and cysteine 10 mM (48±5.65%) led to lower rates of DNA damage, compared to control (P < 0.05). As regards to MDA level, cysteine at 10 mM dose gave the highest level (4.99±0.44 nmol/L) (P < 0.001). GPx activity was demonstrated to be higher level upon the addition of 5 mM cysteine when compared to the other groups (P < 0.05). With respect to fertility results based on 60-day non-returns, the supplementation of antioxidants did not present significant differences (P > 0.05). The results of this study may provide an useful information for the future studies in this area. So, further studies could be suggested to achieve better information in terms of the DNA damage and fertilizing capacity of bull sperm frozen with effective antioxidants.

The effect of raffinose and methionine on frozen/thawed Angora buck (Capra hircus ancryrensis) semen quality, lipid peroxidation and antioxidant enzyme activities.

The aim of the present study was to determine the effects of different doses of raffinose and methionine on post-thawed semen quality, lipid peroxidation and antioxidant enzyme activities of Angora buck (Capra hircus ancryrensis) sperm following cryopreservation. Ejaculates collected from three Angora bucks were evaluated and pooled at 37 degrees C. Semen samples, which were diluted with a Tris-based extender containing the additives raffinose (2.5, 5, 10mM) and methionine (2.5, 5, 10mM) and an extender containing no antioxidants (control), were cooled to 5 degrees C and frozen in 0.25 ml French straws. Frozen straws were thawed individually at 37 degrees C for 20s in a water bath for evaluation. The freezing extender supplemented with 2.5 and 5mM methionine led to higher percentages of CASA motility (63.6+/-7.0; 63.4+/-3.1%, respectively), in comparison to the controls (P<0.01) following the freeze-thawing process. The addition of antioxidants did not provide any significant effect on the percentages of post-thaw subjective and CASA progressive motilities as well as sperm motion characteristics (VSL and VCL), compared to the control groups (P>0.05). The freezing extender with raffinose (5 and 10mM) and methionine at three different doses (2.5, 5 and 10mM) led to lower percentages of acrosome abnormalities, in comparison to the controls (P<0.001). In the comet test, raffinose (5 and 10mM) and methionine (10mM) gave scores lower than those of the controls, and thereby reduced DNA damage (P<0.05). Malondialdehyde formation was found to be lower (1.8+/-0.1 nmol/L) in the group of 5mM raffinose, compared to the controls following the freeze-thawing process (P<0.01). The additives did not show any effectiveness on the maintenance of SOD, GSH-PX and GSH activities, when compared to the controls (P>0.05). In conclusion, methionine and raffinose play a cryoprotective role against sperm CASA motility, acrosome abnormality and DNA damage. Raffinose 5mM exhibited antioxidative properties, decreasing MDA levels. Further studies are required to obtain more concrete results on the characterization of microscopic parameters and antioxidant activities in cryopreserved goat sperm with different additives.