Fano-like Resonance due to Interference with Distant Transitions.

Narrow optical resonances of atoms or molecules have immense significance in various precision measurements, such as testing fundamental physics and the generation of primary frequency standards. In these studies, accurate transition centers derived from fitting the measured spectra are demanded, which critically rely on the knowledge of spectral line profiles. Here, we propose a new mechanism of Fano-like resonance induced by distant discrete levels and experimentally verify it with Doppler-free spectroscopy of vibration-rotational transitions of CO_{2}. The observed spectrum has an asymmetric profile and its amplitude increases quadratically with the probe laser power. Our results facilitate a broad range of topics based on narrow transitions.

Synthetic five-wave mixing in an integrated microcavity for visible-telecom entanglement generation.

Nonlinear optics processes lie at the heart of photonics and quantum optics for their indispensable role in light sources and information processing. During the past decades, the three- and four-wave mixing (χ(2) and χ(3)) effects have been extensively studied, especially in the micro-/nano-structures by which the photon-photon interaction strength is greatly enhanced. So far, the high-order nonlinearity beyond the χ(3) has rarely been studied in dielectric materials due to their weak intrinsic nonlinear susceptibility, even in high-quality microcavities. Here, an effective five-wave mixing process (χ(4)) is synthesized by incorporating χ(2) and χ(3) processes in a single microcavity. The coherence of the synthetic χ(4) is verified by generating time-energy entangled visible-telecom photon pairs, which requires only one drive laser at the telecom waveband. The photon-pair generation rate from the synthetic process shows an estimated enhancement factor over 500 times upon intrinsic five-wave mixing. Our work demonstrates a universal approach of nonlinear synthesis via photonic structure engineering at the mesoscopic scale rather than material engineering, and thus opens a new avenue for realizing high-order optical nonlinearities and exploring functional photonic devices.

Quantum-enhanced radiometry via approximate quantum error correction.

Quantum sensing based on exotic quantum states is appealing for practical metrology applications and fundamental studies. However, these quantum states are vulnerable to noise and the resulting quantum enhancement is weakened in practice. Here, we experimentally demonstrate a quantum-enhanced sensing scheme with a bosonic probe, by exploring the large Hilbert space of the bosonic mode and developing both the approximate quantum error correction and the quantum jump tracking approaches. In a practical radiometry scenario, we attain a 5.3 dB enhancement of sensitivity, which reaches 9.1 × 10-4 Hz-1/2 when measuring the excitation population of a receiver mode. Our results demonstrate the potential of quantum sensing with near-term quantum technologies, not only shedding new light on the quantum advantage of sensing, but also stimulating further efforts on bosonic quantum technologies.

High-Efficiency Arbitrary Quantum Operation on a High-Dimensional Quantum System.

The ability to manipulate quantum systems lies at the heart of the development of quantum technology. The ultimate goal of quantum control is to realize arbitrary quantum operations (AQUOs) for all possible open quantum system dynamics. However, the demanding extra physical resources impose great obstacles. Here, we experimentally demonstrate a universal approach of AQUO on a photonic qudit with the minimum physical resource of a two-level ancilla and a log_{2}d-scale circuit depth for a d-dimensional system. The AQUO is then applied in a quantum trajectory simulation for quantum subspace stabilization and quantum Zeno dynamics, as well as incoherent manipulation and generalized measurements of the qudit. Therefore, the demonstrated AQUO for complete quantum control would play an indispensable role in quantum information science.

Experimental Simulation of Open Quantum System Dynamics via Trotterization.

Digital quantum simulators provide a diversified tool for solving the evolution of quantum systems with complicated Hamiltonians and hold great potential for a wide range of applications. Although much attention is paid to the unitary evolution of closed quantum systems, dissipation and noise are vital in understanding the dynamics of practical quantum systems. In this work, we experimentally demonstrate a digital simulation of an open quantum system in a controllable Markovian environment with the assistance of a single ancillary qubit. By Trotterizing the quantum Liouvillians, the continuous evolution of an open quantum system is effectively realized, and its application in error mitigation is demonstrated by adjusting the simulated noise intensities. High-order Trotter for open quantum dynamics is also experimentally investigated and shows higher accuracy. Our results represent a significant step toward hardware-efficient simulation of open quantum systems and error mitigation in quantum algorithms in noisy intermediate-scale quantum systems.

Heisenberg-limited single-mode quantum metrology in a superconducting circuit.

Two-mode interferometers lay the foundations for quantum metrology. Instead of exploring quantum entanglement in the two-mode interferometers, a single bosonic mode also promises a measurement precision beyond the shot-noise limit (SNL) by taking advantage of the infinite-dimensional Hilbert space of Fock states. Here, we demonstrate a single-mode phase estimation that approaches the Heisenberg limit (HL) unconditionally. Due to the strong dispersive nonlinearity and long coherence time of a microwave cavity, quantum states of the form [Formula: see text] can be generated, manipulated and detected with high fidelities, leading to an experimental phase estimation precision scaling as ∼N-0.94. A 9.1 dB enhancement of the precision over the SNL at N = 12 is achieved, which is only 1.7 dB away from the HL. Our experimental architecture is hardware efficient and can be combined with quantum error correction techniques to fight against decoherence, and thus promises quantum-enhanced sensing in practical applications.

MicroRNA-548-3p and MicroRNA-576-5p enhance the migration and invasion of esophageal squamous cell carcinoma cells via NRIP1 down-regulation.

Nuclear receptor interacting protein (NRIP1), also known as RIP140, is a transcriptional co-regulator required for the maintenance of energy homeostasis and ovulation. Although several studies have identified roles for NRIP1 in various cell processes, the biological functions of NRIP1 in esophageal squamous cell carcinoma (ESCC) remain unknown. Herein, we demonstrate that NRIP1 inhibits the migration and invasion of ESCC cells. Further mechanistic studies revealed that NRIP1 is directly targeted by miR-548-3p and miR-576-5p. We then identified that miR-548-3p and miR-576-5p regulate the migration and invasion of ESCC cells by inhibiting NRIP1 expression. Interestingly, the expression of miR-548-3p and miR-576-5p in ESCC cell lines and ESCC tissues is up-regulated and NRIP1 is down-regulated relative to controls. A statistically significant inverse association was found between the expression levels of miR-548-3p/miR-576-5p and NRIP1. These combined results reveal novel functions for miR-548-3p, miR-576-5p, and NRIP1 in regulating ESCC cell migration and invasion which are important functions for the metastatic process in esophageal cancer.

Fine mapping and characterization of the or gene in Chinese cabbage (Brassica rapa L. ssp pekinensis).

Orange inner leaves/heads is a qualitative trait in Chinese cabbage that is controlled by a single recessive gene. Orange head Chinese cabbage contain more carotenoids than its white head counterpart; hence, this trait is of interest to both researchers and consumers. In this study, we selected the orange head Chinese cabbage line 07A163 and the white head Chinese cabbage line Chiifu as test materials. We localized the target gene controlling the orange head trait to the A09 linkage group, with a physical distance of approximately 19.9 kb between the two markers, syau26 and syau28. This region contains six candidate genes, including Bra031539, which was predicted to encode CRTISO, a carotenoid isomerase specifically required for carotenoid biosynthesis. A comparison of the nucleic acid sequences of the two test materials revealed 88 and 7-bp deletions and 88 SNPs in the promoter region of Bra031539 in line 07A163, along with a 6-bp deletion in the first exon and early termination at the 3' end of this gene. BLAST analysis revealed that 22 amino acids were altered and 17 amino acids were lost in Bra031539 in the orange head line 07A163. We developed the BrPro1 molecular marker in the promoter region of Bra031539 that can be used for early identification of orange head materials, thereby accelerating the breeding process of orange head Chinese cabbage.

Broadband integrated polarization beam splitter with surface plasmon.

A broadband integrated waveguide polarization beam splitter consisting of a metal nanoribbon and two dielectric waveguides is proposed and numerically investigated. This surface plasmon based device provides a unique approach for polarization sensitive manipulation of light in an integrated circuit and will be essential for future classical and quantum information processes.

Negative Goos-Hänchen shift on a concave dielectric interface.

We study the Goos-Hänchen shift (GHS) on a curved surface through numerical simulation by the boundary element method. A negative GHS is first discovered on a concave dielectric interface below the critical angle, accompanied by a large positive GHS on the convexity. The simulation shows that the GHS on a planar interface is the composition of the GHS from a concave and the corresponding convex interface. This work will enrich the study of the GHS for different curved surfaces, which will have potential applications in micro-optics and near-field optics.

Low-threshold microlaser in a high-Q asymmetrical microcavity.

We experimentally report an asymmetrical spherical microcavity with thermal-induced deformation, in which five-bounce whispering-gallery modes possess not only ultrahigh quality factors (Q) but also remarkably directional escape emission from the microsphere boundary. With efficient free-space excitation and collection, a low-threshold microlaser is demonstrated and exhibits a highly directional emission. Our measurement agrees well with the theoretical predictions by corrected Fresnel law.

[Conformational flexibility of enzyme active sites].

Comparative studies of conformation and activity changes of a number of enzymes during denaturation have shown that inactivation generally precedes detectable global conformational changes. Kinetically, the inactivation rates of enzymes during denaturation are much faster than the rates of global conformational changes under identical conditions. It is suggested that the conformation of enzyme active sites are held together by weaker forces and consequently more flexible compared to the molecule as a whole. Conformational changes at the active sites were demonstrated directly by fluorescent and spin probes introduced at the active site of creatine kinase, glyceraldehyde-3-phosphate dehydrogenase and ribonuclease A. In addition, the susceptibility of ribonuclease A to proteolysis is markedly increased in dilute GuHCl. By separation and N-terminal sequence analysis of the peptide fragments liberated by hydrolysis with trypsin or proteinase K, the cleavage points can be identified to show that without gross unfolding of the RNase molecule as a whole, loosening up of active site conformation has indeed occurred during inactivation in dilute GuHCl. For the role of active site flexibility in enzyme catalysis, it is possible that each intermediate step of the whole cycle of catalysis requires the enzyme molecule to be in a different conformation state. Active site flexibility would therefore be essential for the full expression of enzyme activity. It has recently been demonstrated that conformational change, especially that at the active site, accompanies enzyme catalysis and the activation of a number of enzymes involves the loosening up of the active site structure.

Disulfide containing proteins denatured in 6 mol/L guanidinium chloride are not completely unfolded.

The unfolded states of serum albumin, lysozyme and ribonuclease denatured in GuHCl with their disulfide bridges intact or reduced and carboxyamidomethylated have been compared by their circular dichroism, second-derivative and difference spectra in the ultraviolet region. Results obtained indicate that although the secondary structures of denatured proteins with intact disulfides are largely destroyed, they still have considerable ordered conformation even in 6 mol/L guanidinium chloride as indicated by the differences in the extents of exposure of the aromatic residues compared to the denatured proteins without the native disulfide bonds.

Changes in circular dichroism and exposure of buried thiol groups during denaturation of rabbit muscle creatine kinase.

The denaturation of creatine kinase in guanidine solutions has been followed by both CD changes and the increase in rapid reacting SH groups. The rates of the exposure of SH groups are in general agreement with the ultraviolet absorbance and fluorescence changes reported previously whereas changes in the ellipticity of the enzyme molecule can be detected at low guanidine concentrations before significant changes in the exposure of the aromatic residues could be observed. On the other hand, the rates of changes in the mean residue ellipticity at 220 nm are clearly slower than the changes in ultraviolet absorbance, fluorescence and exposure of SH groups. It is suggested that the secondary structure of the external regions of the peptide chains is affected at low guanidine concentrations followed by gross changes in the tertiary structure of the molecule resulting in the exposure of the buried aromatic residues. The destruction of ordered secondary structure of the peptide chain is a slower process than the opening up of the folded tertiary structure of the molecule.

The cooperative behavior of yeast D-glyceraldehyde-3-phosphate. Dehydrogenase as studied by the formation of the fluorescent NAD derivative.

The ultraviolet irradiation of the yeast D-glyceraldehyde-3-phosphate dehydrogenase carboxymethylated at the active site Cys residues, as with the rabbit muscle enzyme, led to the formation of a fluorescent NAD derivative with an emission maximum at 410 nm. Similar results were obtained with the enzyme selectively carboxymethylated at only 2 of its 4 active site Cys residues. The binding of NAD+ to both the carboxymethylated enzymes is non-cooperative or only weakly negatively cooperative when determined by NAD+ quenching of the intrinsic protein fluorescence. However, determinations of the amount of fluorescent NAD derivative formed under different NAD+ concentrations show that both the carboxymethylated enzymes appeared to bind NAD+ with positive cooperativity as in the case of the binding of NAD+ to the native apoenzyme. This seems to suggest that the spatial positioning of the nicotinamide moiety at the active site of the irradiated enzyme resembles more closely that of the nicotinamide ring in the native holoenzyme as compared to the carboxymethylated enzymes.