Assessing a binary quantum channel exploiting a silicon photomultiplier based hybrid receiver.

In quantum communication protocols, the use of photon-number-resolving detectors could open new perspectives by broadening the way to encode and decode information and merging the properties of discrete and continuous variables. In this work, we consider a quantum channel exploiting a silicon-photomultiplier-based receiver and evaluate its performance for quantum communication protocols under three possible configurations, defined by different post-processing of the detection outcomes. We investigate two scenarios: information transmission over the channel, quantified by the mutual information, and continuous-variable quantum key distribution, quantified by the key generation rate.

Lineshape of Amplitude-Modulated Stimulated Raman Spectra.

The amplitude modulation of a pump field and the phase-sensitive detection of a pump-induced intensity change of a probe field encompass a common practice in nonlinear spectroscopies to enhance the detection sensitivity. A drawback of this approach arises when the modulation frequency is comparable to the width of the spectral feature of interest, since the presence of sidebands in the amplitude-modulated pump field provides distortion to the observed spectral lineshape. This represents a problem when accurate measurements of spectral lineshapes and line positions are pursued, as recently happened in our group with the metrology of the Q(1) line in the 1-0 band of molecular hydrogen.

Fast rate dual-comb spectrometer in the water-transparent 7.5-11.5 µm region.

We introduce a dual-comb spectrometer based on erbium fiber oscillators at 250 MHz that operates in the 7.5-11.5 µm spectral range over optical bandwidths up to 9 THz with a multi-kHz acquisition rate.

Mercury Clathration-Driven Phase Transition in a Luminescent Bipyrazolate Metal-Organic Framework: A Multitechnique Investigation.

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1-pyrazol-4-yl)ethyne (HBPE) was expressly designed and synthesized to devise metal-organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·DMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders.

High-resolution molecular fingerprinting in the 11.6-15 µm range by a quasi-CW difference-frequency-generation laser source.

We report an approach for high-resolution spectroscopy using a widely tunable laser emitting in the molecular fingerprint region. The laser is based on difference-frequency generation (DFG) in a nonlinear orientation-patterned GaAs crystal. The signal laser, a CO gas laser, is operated in a kHz-pulsed mode while the pump laser, an external-cavity quantum cascade laser, is finely mode-hop-free tuned.

Standoff CARS spectroscopy and imaging using an ytterbium-based laser system.

A laser system for standoff coherent anti-Stokes Raman scattering (CARS) spectroscopy of various materials under ambient light conditions is presented. The system is based on an ytterbium laser and an ultrafast optical parametric amplifier for the generation of a broadband pump tunable from 880 to 930 nm, a Stokes at 1025 nm, and a narrowband probe at 512.5 nm.

Double-stranded flanking ends affect the folding kinetics and conformational equilibrium of G-quadruplexes forming sequences within the promoter of KIT oncogene.

G-quadruplexes embedded within promoters play a crucial role in regulating the gene expression. KIT is a widely studied oncogene, whose promoter contains three G-quadruplex forming sequences, c-kit1, c-kit2 and c-kit*. For these sequences available studies cover ensemble and single-molecule analyses, although for kit* the latter were limited to a study on a promoter domain comprising all of them.

Author Correction: Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Comb-locked frequency-swept synthesizer for high precision broadband spectroscopy.

Frequency combs have made optical metrology accessible to hundreds of laboratories worldwide and they have set new benchmarks in multi-species trace gas sensing for environmental, industrial and medical applications. However, current comb spectrometers privilege either frequency precision and sensitivity through interposition of a cw probe laser with limited tuning range, or spectral coverage and measurement time using the comb itself as an ultra-broadband probe. We overcome this restriction by introducing a comb-locked frequency-swept optical synthesizer that allows a continuous-wave laser to be swept in seconds over spectral ranges of several terahertz while remaining phase locked to an underlying frequency comb.

Comb-calibrated sub-Doppler spectroscopy with an external-cavity quantum cascade laser at 7.7 μm.

We study the frequency noise and the referencing to a near-infrared frequency comb of a widely tunable external-cavity quantum-cascade-laser that shows a relatively narrow free-running emission linewidth of 1.7 MHz. The frequency locking of the laser to the comb further narrows its linewidth to 690 kHz and enables sub-Doppler spectroscopy on an NO transition of the ν band near 7.

Synthesis and Spectroscopic Characterization of 2-(het)Aryl Perimidine Derivatives with Enhanced Fluorescence Quantum Yields.

Perimidines are a particularly versatile family of heterocyclic compounds, whose properties are exploited in several applications ranging from industrial to medicinal chemistry. The molecular structure of perimidine incorporates a well-known efficient fluorophore, i.e.

Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser.

We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz.

Conjugating precision and acquisition time in a Doppler broadening regime by interleaved frequency-agile rapid-scanning cavity ring-down spectroscopy.

We propose a novel approach to cavity-ring-down-spectroscopy (CRDS) in which spectra acquired with a frequency-agile rapid-scanning (FARS) scheme, i.e., with a laser sideband stepped across the modes of a high-finesse cavity, are interleaved with one another by a sub-millisecond readjustment of the cavity length.

Fluorimetric detection of the earliest events in amyloid β oligomerization and its inhibition by pharmacologically active liposomes.

Background: Amyloid β (Aβ) peptide aggregation is the main molecular mechanism underlying the development of Alzheimer's disease, the most widespread form of senile dementia worldwide. Increasing evidence suggests that the key factor leading to impaired neuronal function is accumulation of water-soluble Aβ oligomers rather than formation of the senile plaques created by the deposition of large fibrillary aggregates of Aβ. However, several questions remain about the preliminary steps and the progression of Aβ oligomerization.

Effects of non-CpG site methylation on DNA thermal stability: a fluorescence study.

Cytosine methylation is a widespread epigenetic regulation mechanism. In healthy mature cells, methylation occurs at CpG dinucleotides within promoters, where it primarily silences gene expression by modifying the binding affinity of transcription factors to the promoters. Conversely, a recent study showed that in stem cells and cancer cell precursors, methylation also occurs at non-CpG pairs and involves introns and even gene bodies.

Full genotyping of a highly polymorphic human gene trait by time-resolved fluorescence resonance energy transfer.

The ability of detecting the subtle variations occurring, among different individuals, within specific DNA sequences encompassed in highly polymorphic genes discloses new applications in genomics and diagnostics. DQB1 is a gene of the HLA-II DQ locus of the Human Leukocyte Antigens (HLA) system. The polymorphisms of the trait of the DQB1 gene including codons 52-57 modulate the susceptibility to a number of severe pathologies.

Elucidation of the relationships between H-bonding patterns and excited state dynamics in cyclovalone.

Cyclovalone is a synthetic curcumin derivative in which the keto-enolic system is replaced by a cyclohexanone ring. This modification of the chemical structure might in principle result in an excited state that is more stable than that of curcumin, which in turn should produce an enhanced phototoxicity. Indeed, although curcumin exhibits photosensitized antibacterial activity, this compound is characterized by very fast excited-state dynamics which limit its efficacy as a photosensitizer.

Spatial properties of twin-beam correlations at low- to high-intensity transition.

It is shown that spatial correlation functions measured for correlated photon pairs at the single-photon level correspond to speckle patterns visible at high intensities. This correspondence is observed for the first time in one experimental setup by using different acquisition modes of an intensified CCD camera in low and high intensity regimes. The behavior of intensity auto- and cross-correlation functions in dependence on pump-beam parameters including power and transverse profile is investigated.