Subcycle quantum electrodynamics.

Squeezed states of electromagnetic radiation have quantum fluctuations below those of the vacuum field. They offer a unique resource for quantum information systems and precision metrology, including gravitational wave detectors, which require unprecedented sensitivity. Since the first experiments on this non-classical form of light, quantum analysis has been based on homodyning techniques and photon correlation measurements. These methods currently function in the visible to near-infrared and microwave spectral ranges. They require a well-defined carrier frequency, and photons contained in a quantum state need to be absorbed or amplified. Quantum non-demolition experiments may be performed to avoid the influence of a measurement in one quadrature, but this procedure comes at the expense of increased uncertainty in another quadrature. Here we generate mid-infrared time-locked patterns of squeezed vacuum noise. After propagation through free space, the quantum fluctuations of the electric field are studied in the time domain using electro-optic sampling with few-femtosecond laser pulses. We directly compare the local noise amplitude to that of bare (that is, unperturbed) vacuum. Our nonlinear approach operates off resonance and, unlike homodyning or photon correlation techniques, without absorption or amplification of the field that is investigated. We find subcycle intervals with noise levels that are substantially less than the amplitude of the vacuum field. As a consequence, there are enhanced fluctuations in adjacent time intervals, owing to Heisenberg's uncertainty principle, which indicate generation of highly correlated quantum radiation. Together with efforts in the far infrared, this work enables the study of elementary quantum dynamics of light and matter in an energy range at the boundary between vacuum and thermal background conditions.

Floquet Spectroscopy of a Strongly Driven Quantum Dot Charge Qubit with a Microwave Resonator.

We experimentally investigate a strongly driven GaAs double quantum dot charge qubit weakly coupled to a superconducting microwave resonator. The Floquet states emerging from strong driving are probed by tracing the qubit-resonator resonance condition. In this way, we probe the resonance of a qubit that is driven in an adiabatic, a nonadiabatic, or an intermediate rate, showing distinct quantum features of multiphoton processes and a fringe pattern similar to Landau-Zener-Stückelberg interference. Our resonant detection scheme enables the investigation of novel features when the drive frequency is comparable to the resonator frequency. Models based on the adiabatic approximation, rotating wave approximation, and Floquet theory explain our experimental observations.

Paraxial Theory of Direct Electro-optic Sampling of the Quantum Vacuum.

Direct detection of vacuum fluctuations and analysis of subcycle quantum properties of the electric field are explored by a paraxial quantum theory of ultrafast electro-optic sampling. The feasibility of such experiments is demonstrated by realistic calculations adopting a thin ZnTe electro-optic crystal and stable few-femtosecond laser pulses. We show that nonlinear mixing of a short near-infrared probe pulse with the multiterahertz vacuum field leads to an increase of the signal variance with respect to the shot noise level. The vacuum contribution increases significantly for appropriate length of the nonlinear crystal, short pulse duration, tight focusing, and a sufficiently large number of photons per probe pulse. If the vacuum input is squeezed, the signal variance depends on the probe delay. Temporal positions with a noise level below the pure vacuum may be traced with subcycle resolution.

The valley Zeeman effect in inter- and intra-valley trions in monolayer WSe2.

Monolayer transition metal dichalcogenides (TMDs) hold great promise for future information processing applications utilizing a combination of electron spin and valley pseudospin. This unique spin system has led to observation of the valley Zeeman effect in neutral and charged excitonic resonances under applied magnetic fields. However, reported values of the trion valley Zeeman splitting remain highly inconsistent across studies. Here, we utilize high quality hBN encapsulated monolayer WSe2 to enable simultaneous measurement of both intervalley and intravalley trion photoluminescence. We find the valley Zeeman splitting of each trion state to be describable only by a combination of three distinct g-factors, one arising from the exciton-like valley Zeeman effect, the other two, trion specific, g-factors associated with recoil of the excess electron. This complex picture goes significantly beyond the valley Zeeman effect reported for neutral excitons, and eliminates the ambiguity surrounding the magneto-optical response of trions in tungsten based TMD monolayers.

Resonantly driven CNOT gate for electron spins.

Single-qubit rotations and two-qubit CNOT operations are crucial ingredients for universal quantum computing. Although high-fidelity single-qubit operations have been achieved using the electron spin degree of freedom, realizing a robust CNOT gate has been challenging because of rapid nuclear spin dephasing and charge noise. We demonstrate an efficient resonantly driven CNOT gate for electron spins in silicon. Our platform achieves single-qubit rotations with fidelities greater than 99%, as verified by randomized benchmarking. Gate control of the exchange coupling allows a quantum CNOT gate to be implemented with resonant driving in ~200 nanoseconds. We used the CNOT gate to generate a Bell state with 78% fidelity (corrected for errors in state preparation and measurement). Our quantum dot device architecture enables multi-qubit algorithms in silicon.

Aminoacylation of Phaseolus vulgaris cytoplasmic, chloroplastic and mitochondrial tRNAsPro and tRNAsLys by homologous and heterologous enzymes.

The cytoplasmic prolyl-tRNA synthetase can be separated by hydroxyapatite chromatography, from the enzyme present in the chloroplasts and in the mitochondria (organellar enzyme). The cytoplasmic lysyl-tRNA synthetase can also be separated from the organellar enzyme. There are two tRNAsPro in the cytoplasm; they can be charged by the cytoplasmic enzyme, but not by the organellar enzyme or the Escherichia coli enzyme. Chloroplasts contain, in addition to the two cytoplasmic tRNAsPro, one chloroplast-specific tRNAPro, which is not recognized by the cytoplasmic enzyme, but can be charged by the organellar or the E. coli enzyme. Mitochondria contain, in addition to the two cytoplasmic tRNAsPro, two mitochondria-specific tRNAsPro, which are not recognized by the cytoplasmic enzyme, but can be charged by the organellar or the E. coli enzyme. There are two tRNAsLys in the cytoplasm. Both can be charged by the cytoplasmic enzyme, but one can be charged by the organellar or E. coli enzyme. Chloroplasts contain in addition to one cytoplasmic tRNALys, one chloroplast-specific tRNALys which can only be charged by the organellar or E. coli enzyme. Mitochondria contain, in addition to one cytoplasmic tRNALys, one mitochondria-specific tRNALys which can only be charged by the organellar or E. coli enzyme.

Aminoacylation of tRNA-Leu species from Escherichia coli and from the cytoplasm, chloroplasts and mitochondria of Phaseolus vulgaris by homologous and heterologous enzymes.

Leucyl-tRNA synthetase from Phaseolus vulgaris chloroplasts could be separated from its cytoplasmic counterpart upon chromatography on hydroxyapatite, but the cytoplasmic and mitochondrial leucyl-tRNA synthetases could not be distinguished. The tRNALeu species from the various plant cell compartments and from Escherichia coli were aminoacylated using either homologous or heterologous enzymes; the levels of aminoacylation and the profiles of the leucyl-tRNAs upon reverse-phase chromatography were studied. Cytoplasmic tRNALeu species could be aminoacylated by the cytoplasmic or by the mitochondrial enzymes and in both cases yielded two peaks upon reverse-phase chromatography (RPC-5). But they could not be charged by the chloroplast-specific or by the E. coli enzynes. Mitochondrial tRNALeu species could be charged by the mitochondrial or by the cytoplasmic enzymes and in both cases yielded four peaks upon reverse phase (RPC-5) chromatography. But they could not be aminoacylated using the chloroplast-specific or the E. coli leucyl-tRNA synthetases. Chloroplastic tRNALeu species can be divided into two classes: the first class contains four isoacceptor species which can be charged by the cytoplasmic or mitochondrial enzymes, but not by the chloroplast-specific or the E. coli enzymes; the second class contains three chloroplast-specific tRNALeu species which can be charged by the chloroplast-specific or the E. coli enzymes but not by the cytoplasmic or the mitochondrial enzymes. There are five isoacceptor tRNALeu species in E. coli; all are charged by the E. coli or the chloroplast-specific enzymes, while only one is aminoacylated by the plant cytoplasmic or mitochondrial enzymes.

Hybridization of bean, spinach, maize and Euglena chloroplast transfer RNAs with homologous and heterologous chloroplast DNAs. An approach to the study of homology between chloroplast tRNAs from various species.

Chloroplast tRNAs from two dicotyledons (spinach and bean), a monocotyledon (maize) and a green alga (Euglena) have been fractionated by two-dimensional gel electrophoresis. The individual tRNAs have been identified, albeled with 125I or 32P, and used in tRNA-DNA hybridization experiments. Spinach chloroplast tRNAs hybridize as well, and maize chloroplast tRNAs almost as well as bean chloroplast tRNAs to bean chloroplast DNA, thus suggesting a high degree of homology between the chloroplast tRNAs from the two dicotyledons and between the tRNAs from the two dicotyledons and those of the monocotyledon. But Euglena total chloroplast tRNA hybridizes very poorly to bean chloroplast DNA, and among the 14 individual tRNAs tested, only one, Euglena chloroplast tRNAPhe, hybridizes to both maize and bean chloroplast DNAs, which is in good agreement with the fact that Euglena and bean chloroplast tRNAsPhe have almost identical primary structures.

The complete amino acid sequence of the pathogenesis-related (PR2) protein induced in chemically stressed bean leaves.

We have established the complete sequence of the 155 amino acid residues of the pathogenesis-related protein PR2 accumulating in bean leaves treated with a mercuric chloride solution. Bean PR2 whose biological function remains to be elucidated, represents a structurally unfamiliar protein in which sequence arginine, cysteine, methionine and tryptophan residues are missing. This sequence is identical to that of bean PvPR1.

Direct sampling of electric-field vacuum fluctuations.

The ground state of quantum systems is characterized by zero-point motion. This motion, in the form of vacuum fluctuations, is generally considered to be an elusive phenomenon that manifests itself only indirectly. Here, we report direct detection of the vacuum fluctuations of electromagnetic radiation in free space. The ground-state electric-field variance is inversely proportional to the four-dimensional space-time volume, which we sampled electro-optically with tightly focused laser pulses lasting a few femtoseconds. Subcycle temporal readout and nonlinear coupling far from resonance provide signals from purely virtual photons without amplification. Our findings enable an extreme time-domain approach to quantum physics, with nondestructive access to the quantum state of light. Operating at multiterahertz frequencies, such techniques might also allow time-resolved studies of intrinsic fluctuations of elementary excitations in condensed matter.

Construction of the physical map of the chloroplast DNA of Phaseolus vulgaris and localization of ribosomal and transfer RNA genes.

Construction of a physical map of the chloroplast DNA from Phaseolus vulgaris showed that this circular molecule is segmentally organized into four regions. Unlike other chloroplast DNAs which have analogous organization, two single-copy regions that separate two inverted repeats have been demonstrated to exist in both relative orientations, giving rise to two populations of DNA molecules. Hybridization studies using individual rRNA and tRNA species revealed the location of a set of rRNA genes and at least seven tRNA genes in each inverted repeat region, a minimum of 17 tRNA genes in the large single-copy region and one tRNA gene in the small single-copy region. The tRNA genes code for 24 tRNA species corresponding to 16 amino acids. Comparison of this gene map with those of other chloroplast DNAs suggests that DNA sequence rearrangements, involving some tRNA genes, have occurred.

Fractionation and identification of spinach chloroplast transfer RNAs and mapping of their genes on the restriction map of chloroplast DNA.

Spinach chloroplast 4S RNAs has been separated by two-dimensional polyacrylamide gel electrophoresis into about 35 species. After extraction from the gel, 27 of these RNA species were identified by aminoacylation as tRNAs specific for 16 amino acids. Individual tRNAs were labeled in vitro with 125I and hybridized to DNA fragments obtained by digestion of spinach chloroplast DNA with KpnI, PstI, SalI and XmaI restriction endonucleases. A minimum of 21 genes corresponding to tRNAs for 14 different amino acids have been localized on the restriction endonuclease cleavage site map of the DNA molecule. Of these, 15 genes corresponding to tRNAs for 12 amino acids are located in the larger of the two single-copy regions which separate the two inverted copies of the repeat region. Each copy of this repeat region contains a set of genes for the ribosomal RNAs and a gene for tRNA2Ile in the "spacer" sequence between the 16S and 23S ribosomal RNAs. The genes for tRNA1Ile, tRNA2Leu and tRNA3Leu also map in the repeat region, but outside the ribosomal DNA unit. At present, two more chloroplast tRNAs (for Pro and Lys) have been identified, but not mapped, while 4 unidentified 4S RNAs have been mapped in the large single-copy region of the DNA molecule. Evidence is presented that isoaccepting tRNA species can be transcripts from different loci.

Benefits and risks of the hypericum extract LI 160: drug monitoring study with 3250 patients.

Effectiveness and acceptance of a 4-week treatment with hypericum extract LI 160 were investigated by 663 private practitioners. The results of the 3250 patients (76% women and 24% men), were recorded using data sheets. The age of the patients ranged from 20 to 90 years (mean 51 years). Of the patients, 49% were mildly depressed, 46% intermediate, and 3% severely depressed. In about 30% of the patients, the situation normalized or improved during the therapy. Undesired drug effects were reported in 79 (2.4%) patients and 48 (1.5%) discontinued the therapy. Most frequently noted side effects were gastrointestinal irritations (0.6%), allergic reactions (0.5%), tiredness (0.4%), and restlessness (0.3%).

Dephasing of a superconducting qubit induced by photon noise.

We have studied the dephasing of a superconducting flux qubit coupled to a dc-SQUID based oscillator. By varying the bias conditions of both circuits we were able to tune their effective coupling strength. This allowed us to measure the effect of such a controllable and well-characterized environment on the qubit coherence. We can quantitatively account for our data with a simple model in which thermal fluctuations of the photon number in the oscillator are the limiting factor. In particular, we observe a strong reduction of the dephasing rate whenever the coupling is tuned to zero. At the optimal point we find a large spin-echo decay time of .

[Long-term study "Neurodermatitis therapy using urea-containing Externa"]. / Langzeitstudie "Neurodermitis-Therapie mit harnstoffhaltigen Externa".

A long-term study on the therapy of atopic dermatitis with topical urea agents was conducted by over 400 practising dermatologists and pediatricians in Western Germany from March 1989 to March 1991. 1905 patients of all ages who had a baseline diagnosis of acute exacerbation of their neurodermatic skin condition were entered into this open, uncontrolled, multicenter study. Acute attacks were treated with a combination of hydrocortisone and urea. Once the acute symptoms had subsided, therapy was continued with a 10% urea ointment. Over the 12-month observational period, a total of 84% of the patients were exclusively treated with the two trial preparations and only 16% additionally required other corticosteroids.

[Procedures for the quantitative follow-up control of computerized perimetric findings in glaucoma]. / Verfahren zur quantitativen Verlaufskontrolle computerperimetrischer Befunde bei Glaukom.

A statistical model for long-term follow-up of glaucomatous visual fields is described. Using an analysis of individual testpoints, a statistical evaluation of visual field change is done by the Bowker symmetry test. Eccentricity of test points in the visual field, density of scotomas and number of defective test points were used as parameters. The authors demonstrate that evaluation with this method is superior to methods using total sensitivity loss or mean sensitivity of the visual field. This model is currently being used in a retrospective and a prospective glaucoma study.