11 research outputs found
On-demand generation of background--free single photons from a solid-state source
True on--demand high--repetition--rate single--photon sources are highly
sought after for quantum information processing applications. However, any
coherently driven two-level quantum system suffers from a finite re-excitation
probability under pulsed excitation, causing undesirable multi--photon
emission. Here, we present a solid--state source of on--demand single photons
yielding a raw second--order coherence of
without any background subtraction nor data processing. To this date, this is
the lowest value of reported for any single--photon source even
compared to the previously best background subtracted values. We achieve this
result on GaAs/AlGaAs quantum dots embedded in a low--Q planar cavity by
employing (i) a two--photon excitation process and (ii) a filtering and
detection setup featuring two superconducting single--photon detectors with
ultralow dark-count rates of and , respectively. Re--excitation processes are dramatically suppressed by
(i), while (ii) removes false coincidences resulting in a negligibly low noise
floor
Proteomics of industrial fungi: trends and insights for biotechnology
Filamentous fungi are widely known for their industrial applications, namely, the production of food-processing enzymes and metabolites such as antibiotics and organic acids. In the past decade, the full genome sequencing of filamentous fungi increased the potential to predict encoded proteins enormously, namely, hydrolytic enzymes or proteins involved in the biosynthesis of metabolites of interest. The integration of genome sequence information with possible phenotypes requires, however, the knowledge of all the proteins in the cell in a system-wise manner, given by proteomics. This review summarises the progress of proteomics and its importance for the study of biotechnological processes in filamentous fungi. A major step forward in proteomics was to couple protein separation with high-resolution mass spectrometry, allowing accurate protein quantification. Despite the fact that most fungal proteomic studies have been focused on proteins from mycelial extracts, many proteins are related to processes which are compartmentalised in the fungal cell, e.g. ÎČ-lactam antibiotic production in the microbody. For the study of such processes, a targeted approach is required, e.g. by organelle proteomics. Typical workflows for sample preparation in fungal organelle proteomics are discussed, including homogenisation and sub-cellular fractionation. Finally, examples are presented of fungal organelle proteomic studies, which have enlarged the knowledge on areas of interest to biotechnology, such as protein secretion, energy production or antibiotic biosynthesis
Free energy simulations of methane solvation : a study of integrand convergence properties using thermodynamic integration
This report presents the results of free energy simulations using thermodynamic integration (TI) to calculate the absolute free energy of solvation of methane. The dependence of the integrand on the form of the scaling of the Hamiltonian and the extent of the "growth" of the methane was studied. When the methane-water potential is scaled by between 0.002 and 0.15, the integrand became very noisy and the individual values had high statistical uncertainties. This region was responsible for the major contribution to the total integral. A value for the Helmholtz free energy of solvation of 1.23 kcal/mol was obtained, in comparison to the experimental value of 2.005 kcal/mol. It is evident that the calculation has not as yet converged
On-demand generation of background-free single photons from a solid-state source
True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g(2)(0)=(7.5±1.6)Ă10-5 without any background subtraction or data processing. To this date, this is the lowest value of g(2)(0) reported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056±0.0007) s-1 and (0.017±0.001) s-1, respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.QN/Zwiller La