Indistinguishable telecom band photons from a single Er ion in the solid state.

Atomic defects in the solid state are a key component of quantum repeater networks for long-distance quantum communication1. Recently, there has been significant interest in rare earth ions2-4, in particular Er3+ for its telecom band optical transition5-7 that allows long-distance transmission in optical fibres. However, the development of repeater nodes based on rare earth ions has been hampered by optical spectral diffusion, precluding indistinguishable single-photon generation. Here, we implant Er3+ into CaWO4, a material that combines a non-polar site symmetry, low decoherence from nuclear spins8 and is free of background rare earth ions, to realize significantly reduced optical spectral diffusion. For shallow implanted ions coupled to nanophotonic cavities with large Purcell factor, we observe single-scan optical linewidths of 150 kHz and long-term spectral diffusion of 63 kHz, both close to the Purcell-enhanced radiative linewidth of 21 kHz. This enables the observation of Hong-Ou-Mandel interference9 between successively emitted photons with a visibility of V = 80(4)%, measured after a 36 km delay line. We also observe spin relaxation times T1,s = 3.7 s and T2,s > 200 µs, with the latter limited by paramagnetic impurities in the crystal instead of nuclear spins. This represents a notable step towards the construction of telecom band quantum repeater networks with single Er3+ ions.

Hybrid microwave-optical scanning probe for addressing solid-state spins in nanophotonic cavities.

Spin-photon interfaces based on solid-state atomic defects have enabled a variety of key applications in quantum information processing. To maximize the light-matter coupling strength, defects are often placed inside nanoscale devices. Efficiently coupling light and microwave radiation into these structures is an experimental challenge, especially in cryogenic or high vacuum environments with limited sample access. In this work, we demonstrate a fiber-based scanning probe that simultaneously couples light into a planar photonic circuit and delivers high power microwaves for driving electron spin transitions. The optical portion achieves 46% one-way coupling efficiency, while the microwave portion supplies an AC magnetic field with strength up to 9 Gauss at 10 Watts of input microwave power. The entire probe can be scanned across a large number of devices inside a 3He cryostat without free-space optical access. We demonstrate this technique with silicon nanophotonic circuits coupled to single Er3+ ions.

Surface-emitting red, green, and blue colloidal quantum dot distributed feedback lasers.

We demonstrate surface emitting distributed feedback (DFB) lasers across the red, green, and blue from densely packed colloidal quantum dot (CQD) films. The solid CQD films were deposited on periodic grating patterns to enable 2nd-order DFB lasing action at mere 120, 280, and 330 µJ/cm2 of optical pumping energy densities for red, green, and blue DFB lasers, respectively. The lasers operated in single mode operation with less than 1 nm of full-width-half-maximum. We measured far-field patterns showing high degree of spatial beam coherence. Specifically, by taking advantage of single exciton optical gain regime from our engineered CQDs, we can significantly suppress the Auger recombination to reduce lasing threshold and achieve quasi-steady state, optically pumped operation.

Cavity-coupled telecom atomic source in silicon.

Novel T centers in silicon hold great promise for quantum networking applications due to their telecom band optical transitions and the long-lived ground state electronic spins. An open challenge for advancing the T center platform is to enhance its weak and slow zero phonon line (ZPL) emission. In this work, by integrating single T centers with a low-loss, small mode-volume silicon photonic crystal cavity, we demonstrate an enhancement of the fluorescence decay rate by a factor of F = 6.89. Efficient photon extraction enables the system to achieve an average ZPL photon outcoupling rate of 73.3 kHz under saturation, which is about two orders of magnitude larger than the previously reported value. The dynamics of the coupled system is well modeled by solving the Lindblad master equation. These results represent a significant step towards building efficient T center spin-photon interfaces for quantum information processing and networking applications.

Effect of Drug-Coated Balloon Versus Stent Angioplasty in Patients With Symptomatic Intracranial Atherosclerotic Stenosis.

BACKGROUND AND OBJECTIVES: Drug-coated balloons (DCBs) have exhibited promising results in coronary and peripheral artery diseases, but conclusive evidence is lacking in intracranial vasculature. We assessed the safety and efficacy of DCBs vs stent angioplasty for symptomatic intracranial atherosclerotic stenosis (sICAS) and initially identified patients who might have benefited most from DCB treatment. METHODS: A single-center, retrospective cohort study was conducted from June 2021 to May 2022 with 154 patients with sICAS divided into 2 treatment groups: a DCB group (with or without remedial stenting, n = 47) and a stent group (n = 107). The treatment outcomes were compared using 1:2 propensity score matching. The primary safety end point was perioperative stroke or mortality, and the primary efficacy end point was the rate of target vessel restenosis at 12 months. The degree of luminal change was analyzed as a subgroup, defined as the difference between the degree of stenosis at follow-up and immediately after intervention. RESULTS: One hundred eighteen patients were enrolled using propensity score matching, with 43 patients in the DCB group and 75 in the stent group. The incidence of perioperative adverse events was 2.3% in the DCB group and 8.0% in the stent group (P = .420). At a median follow-up of 12 months, the incidence of restenosis (11.9% [5/43] vs 28.0% [21/75], P = .045) and the median degree of stenosis (30% [20%, 44%] vs 30% [30%, 70%], P = .009, CI [0-0.01, 0.2]) were significantly lower in the DCB group than in the stent group. DCB angioplasty effectively prevented adverse events in the target vessel area and significantly reduced the degree of luminal change in the M1 segment of the middle cerebral artery (0 [0, 15%] vs 10% [0, 50%], P = .016). CONCLUSION: DCB angioplasty might be a safe and effective alternative to stent angioplasty to treat sICAS, particularly among patients with M1 segment of the middle cerebral artery stenosis.

The evolution of cropping structure in prehistoric Xizang.

The origin and spread of agriculture facilitated a decline in human mobility and eventually led to a predominantly sedentary lifestyle globally, including on the Tibetan Plateau. Previous studies have proposed an evolution of prehistoric agriculture, from millet-based to barley-based farming. However, details regarding the process are vague. Here, we present diachronic changes in cropping structure from Xizang on the basis of a quantitative analysis of archaeobotanical remains from 12 sites located in southeastern Xizang. The advent of agriculture in Xizang began in the southeastern region around 4800 cal a BP and resulted in a quick spread of millet agriculture from the Hengduan Mountains to the Yarlung Zangbo River region. Subsequently, the introduction of barley and wheat in Xizang led to the transformation of millet-based farming into mixed farming after 3600 cal a BP. Eventually, around 3000 cal a BP, barley and wheat dominated across the entire Xizang with declining occurrences of millet. It took more than 600 years for barley and wheat to dominate in the Tibetan cropping system, which may reflect the time required for these exotic species to adapt physiologically to their new niche. In addition to the diachronic changes in crop farming, the ratio of barley to wheat and foxtail millet to broomcorn millet also varied at different elevations possibly due to local environmental variations and the crops' physiological requirements.

Fabricated ZnO@ZnIn2S4 S-scheme heterojunction photocatalyst for enhanced electron-transfer and CO2 reduction.

Step-scheme (S-scheme) heterojunctions can efficiently promote the separation of photogenerated carriers while maintaining the strong oxidation/reduction ability of photocatalysts; thus, research attention on S-scheme heterojunctions is increasing year by year. In this study, the S-scheme ZnO@ZnIn2S4 (ZnO@ZIS) heterojunction was prepared successfully. Then, electron spin resonance (ESR) characterization was applied to prove the successful construction of the S-scheme heterojunction. Photoluminescence (PL), time-resolved photoluminescence (TRPL), and photoelectrochemical experiments have demonstrated efficient interfacial charge transport in ZnO@ZIS. Finally, the mechanism of CO2 activation and electron transport was investigated by in situ Fourier transform infrared spectroscopy (FT-IR) and discrete Fourier transform (DFT) calculation analysis. The 40-ZnO@ZIS composite showed the best activity under light, and its CO and CH4 yields reached 39.76 and 3.92 µmol∙g-1∙h-1, respectively. This study provides a solution for optimizing the photocatalytic reduction activity of semiconductor photocatalysts by constructing S-scheme heterojunction materials to improve the CO2 reduction capacity.

Torrefaction characteristics of cellulose loaded with boric acid.

To explore the catalytic effect of boric acid on biomass, cellulose loaded with boric acid was roasted by a tubular furnace. The gaseous products were adsorbed by activated carbon and then analyzed by GC-MS. Boric acid was shown to improve the selectivity of the product levoglucosenone (LGO). The effects of the parameters such as boric acid loading, nitrogen flow, and temperature on the torrefaction behavior of cellulose were investigated. In the studied temperature range of 240-420 °C, the yield of LGO first increases and then decreases. In addition, its yield increases directly with increasing nitrogen flow rate. The results show that the highest LGO yield of 6.64% (analytical value) can be obtained under 10% (w/w) boric acid loading, 380 °C and nitrogen flow rate of 65 ml/min conditions.

The potential of a natural iron ore residue application in the efficient removal of tetracycline hydrochloride from an aqueous solution: insight into the degradation mechanism.

In the existing research, most of the heterogeneous catalysts applied in the activation of persulfate to degrade organic pollutants were synthesized from chemical reagents in the laboratory. In this paper, we have obtained a spent iron ore (IO) residue directly collecting from the iron ore plants, and efficiently activating peroxydisulfate (PS) to produce reactive free radicals. The experimental results demonstrated that the IO could effectively activate PS to degrade tetracycline hydrochloride (TCH), with TCH removal rate reaching up to 85.6% within 2 h at room temperature. The TCH removal rate was increased with increasing iron ore dosage, while the more acidic pH condition would be favorable to TCH removal process. The material characterization results demonstrated that the dominant components of IO were Fe3O4 and FeOOH. The transformation from Fe(II) to Fe(III) at the surface IO was observed after TCH degradation. What's more, the quenching experiment and EPR detection results confirmed that the sulfate radical (SO4•-) and hydroxyl radicals (•OH) would be acting as the main free radicals for TCH degradation. This study could not only explore a novel way to recycle the discarded iron ore, but also further expand its application in an effective activation of PS in an aqueous solution.

Parallel single-shot measurement and coherent control of solid-state spins below the diffraction limit.

Solid-state spin defects are a promising platform for quantum science and technology. The realization of larger-scale quantum systems with solid-state defects will require high-fidelity control over multiple defects with nanoscale separations, with strong spin-spin interactions for multi-qubit logic operations and the creation of entangled states. We demonstrate an optical frequency-domain multiplexing technique, allowing high-fidelity initialization and single-shot spin measurement of six rare-earth (Er3+) ions, within the subwavelength volume of a single, silicon photonic crystal cavity. We also demonstrate subwavelength control over coherent spin rotations by using an optical AC Stark shift. Our approach may be scaled to large numbers of ions with arbitrarily small separation and is a step toward realizing strongly interacting atomic defect ensembles with applications to quantum information processing and fundamental studies of many-body dynamics.

Optical quantum nondemolition measurement of a single rare earth ion qubit.

Optically-interfaced spins in the solid state are a promising platform for quantum technologies. A crucial component of these systems is high-fidelity, projective measurement of the spin state. Here, we demonstrate single-shot spin readout of a single rare earth ion qubit, Er3+, which is attractive for its telecom-wavelength optical transition and compatibility with silicon nanophotonic circuits. In previous work with laser-cooled atoms and ions, and solid-state defects, spin readout is accomplished using fluorescence on an optical cycling transition; however, Er3+ and other rare earth ions generally lack strong cycling transitions. We demonstrate that modifying the electromagnetic environment around the ion can increase the strength and cyclicity of the optical transition by several orders of magnitude, enabling single-shot quantum nondemolition readout of the ion's spin with 94.6% fidelity. We use this readout to probe coherent dynamics and relaxation of the spin.

[Combination of separation/preconcentration based on nanoscale TiO2 and FAAS for the simultaneous determination of Cr(III)/Cr(VI) in water].

The nanometer-sized materials have attracted much interest of analysts in recent years because of their special physicschemistry characteristics. As the scale decreases to nanometer grade, the number of atoms on the surface increases remarkably, resulting in the unsaturation. This makes the nanometer-sized materials have a high adsorptivity for the metal atoms. In the present paper, the nanometer-sized TiO2 was applied in the separation and preconcentration of Cr(III) and Cr(VI) in water. The influence of pH on the adsorption of Cr(III) and Cr(VI) was studied. When pH is larger than 6, 90%, Cr(III) is adsorbed onto the nanometer-sized material surface, while is basically not adsorbed in aqueous solution. Therefore, the separation of Cr(III) and Cr(VI) is achieved. At the pH of 6.5, Cr(III) was adsorbed by nanometer-sized TiO2 and desorbed with 2.0 mol x L(-1) HCl, in which the Cr(III) could be preconcentrated. The Cr(III) solution, as well as the Cr(VI) aqueous solution was determined by FAAS. The detection limits of Cr(M) and Cr(VI) were 41 and 57 ng x mL(-1), respectively. And the linear ranges for Cr(III) and Cr(VI) were 0-9.0 microg x mL(-1) and 0.1-10 microg x mL(-1) with a RSDs of 2.6% and 3.4% (n=6, c = 2.0 microg x mL(-1), respectively. This method was applied in the simultaneous determination of Cr(III) and Cr(VI) in the industrial wastewater and river water, and the satisfactory recovery results were obtained.

CO/O2 assisted oxidative carbon-carbon and carbon-heteroatom bond cleavage for the synthesis of oxosulfonates from DMSO and olefins.

Selective carbon-carbon and carbon-heteroatom bond cleavage was achieved in a one reaction system. With this strategy a novel Pd/Cu-catalyzed aerobic oxidative oxosulfonation of olefins with DMSO has been developed. Preliminary mechanistic investigations indicated that CO/O2 assisted the bond cleavage and the leaving groups from the starting materials were trapped by O2 and underwent a hydroxylation process.

High-Q, Low-Threshold Monolithic Perovskite Thin-Film Vertical-Cavity Lasers.

A vertical-cavity surface-emitting perovskite laser is achieved using a microcavity configuration where CH3 NH3 PbI3 thin solid films are embedded within a custom GaN-based high-quality (Q-factor) resonator. This single-mode perovskite laser reaches a low threshold (≈7.6 µJ cm-2 ) at room temperature and emits spatially coherent Gaussian laser beams. The devices allow direct access to the study of perovskite gain dynamics and material robustness.

A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films.

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 µJ/cm(2). The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%, respectively. Importantly, our approach enables scalability of the thin film lasers to a two-dimensional multielement pixelated array of microlasers which we demonstrate as a proof-of-concept for possible projection display applications.

Silver-mediated selective oxidative cross-coupling between C-H/P-H: a strategy to construct alkynyl(diaryl)phosphine oxide.

A direct oxidative cross-coupling between terminal alkynes and secondary phosphine oxides was developed. This approach provides an efficient way to construct alkynyl di(phenyl) phosphine oxides from basic materials, and in this process, the silver salts act as a key promoter.