Model and Measurements of an Optical Stack for Broadband Visible to Near-Infrared Absorption in TiN MKIDs.

Typical materials for optical Microwave Kinetic Inductance Detetectors (MKIDs) are metals with a natural absorption of ∼ 30-50% in the visible and near-infrared. To reach high absorption efficiencies (90-100%) the KID must be embedded in an optical stack. We show an optical stack design for a 60 nm TiN film. The optical stack is modeled as sections of transmission lines, where the parameters for each section are related to the optical properties of each layer. We derive the complex permittivity of the TiN film from a spectral ellipsometry measurement. The designed optical stack is optimised for broadband absorption and consists of, from top (illumination side) to bottom: 85 nm SiO2, 60 nm TiN, 23 nm of SiO2, and a 100 nm thick Al mirror. We show the modeled absorption and reflection of this stack, which has >80% absorption from 400 to 1550 nm and near-unity absorption for 500-800 nm. We measure transmission and reflection of this stack with a commercial spectrophotometer. The results are in good agreement with the model.

Ultrasensitive Kilo-Pixel Imaging Array of Photon Noise-Limited Kinetic Inductance Detectors Over an Octave of Bandwidth for THz Astronomy.

We present the development of a background-limited kilo-pixel imaging array of ultrawide bandwidth kinetic inductance detectors (KIDs) suitable for space-based THz astronomy applications. The array consists of 989 KIDs, in which the radiation is coupled to each KID via a leaky lens antenna, covering the frequency range between 1.4 and 2.8 THz. The single pixel performance is fully characterised using a representative small array in terms of sensitivity, optical efficiency, beam pattern and frequency response, matching very well its expected performance. The kilo-pixel array is characterised electrically, finding a yield larger than 90% and an averaged noise-equivalent power lower than 3  ×  10 - 19  W/Hz 1 / 2 . The interaction between the kilo-pixel array and cosmic rays is studied, with an expected dead time lower than 0.6% when operated in an L2 or a similar far-Earth orbit.

Experimentally simulating the dynamics of quantum light and matter at deep-strong coupling.

The quantum Rabi model describing the fundamental interaction between light and matter is a cornerstone of quantum physics. It predicts exotic phenomena like quantum phase transitions and ground-state entanglement in ultrastrong and deep-strong coupling regimes, where coupling strengths are comparable to or larger than subsystem energies. Demonstrating dynamics remains an outstanding challenge, the few experiments reaching these regimes being limited to spectroscopy. Here, we employ a circuit quantum electrodynamics chip with moderate coupling between a resonator and transmon qubit to realise accurate digital quantum simulation of deep-strong coupling dynamics. We advance the state of the art in solid-state digital quantum simulation by using up to 90 second-order Trotter steps and probing both subsystems in a combined Hilbert space dimension of ∼80, demonstrating characteristic Schrödinger-cat-like entanglement and large photon build-up. Our approach will enable exploration of extreme coupling regimes and quantum phase transitions, and demonstrates a clear first step towards larger complexities such as in the Dicke model.

Superconducting Coplanar Waveguide Filters for Submillimeter Wave On-Chip Filterbank Spectrometers.

We show the first experimental results which prove that superconducting NbTiN coplanar-waveguide resonators can achieve a loaded Q factor in excess of 800 in the 350 GHz band. These resonators can be used as narrow band pass filters for on-chip filter bank spectrometers for astronomy. Moreover, the low-loss coplanar waveguide technology provides an interesting alternative to microstrip lines for constructing large scale submillimeter wave electronics in general.

Probing dynamics of an electron-spin ensemble via a superconducting resonator.

We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25-1.2 K) and polarizing magnetic field (80-300 mT). Measurements exploit field-controlled coupling of the ensemble to two modes of a transmission-line resonator. The observed temperature-independent spin relaxation time indicates that spin outdiffusion across the mode volume dominates over spin-lattice relaxation. Depolarization of one hyperfine-split subensemble by pumping of another indicates fast cross relaxation, with implications for the use of subensembles as independent quantum memories.

Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control.

An intermediate frequency (IF) band digitizing radiometer system in the 100-200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototype system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.

Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization.

A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200,000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

Strong scattering of high power millimeter waves in tokamak plasmas with tearing modes.

In tokamak plasmas with a tearing mode, strong scattering of high power millimeter waves, as used for heating and noninductive current drive, is shown to occur. This new wave scattering phenomenon is shown to be related to the passage of the O point of a magnetic island through the high power heating beam. The density determines the detailed phasing of the scattered radiation relative to the O-point passage. The scattering power depends strongly nonlinearly on the heating beam power.

Les champignons dans les pharmacopees traditionnelles de l'Afrique de l'Ouest

Ce premier inventaire; non exhaustif; des champignons superieurs utilises en pharmacopee traditionnelle en Afrique de l'Ouest; nous revele une richesse insoupconnee pour une region aride et consideree comme ayant une flore mycologique pauvre. Or les populations locales n'ont pas neglige l'apport des champignons dans la pharmacopee; leur usage semblant meme plus important que dans les pharmacopees occidentales qui; a de rares exceptions; ont neglige les champignons; sauf bien entendu les champignons inferieurs generateurs d'antibiotiques (bezanger-beauquesne; 1983). Il y aurait peut-etre interet a approfondir les recherches de ce cote la; nen particulier l'analyse chimique; qui ne devrait pas decevoir; en raison de la richesse previsible des champignons superieurs en molecules d'interet biologique

First syntheses of ectomycorrhizas between Afzelia africana Sm. (Caesalpinioideae) and native fungi from West Africa.

Afzelia-associated fungi in Senegal were isolated from sporocarps, sclerotia and ectomycorrhizas. The choice of sterilizing agent was critical for the success of isolation. Osmic acid was more efficient than mercuric chloride, hydrogen peroxide and calcium hypochlorite. Isolates were tested for their ability to form mycorrhizas in vitro and their mycelia in pure culture were described. Sclerotia linked to mycorrhizas of Scleraderma verrucosum Pers. were also isolated and their infectivity checked. Among isolates from sporocarps, only Scleroderma dictvosparum Fat. and S. verrucosum Pers. formed ectomycorrhizas with Afzelia africana Sm. Two native Amanita spp. and two introduced isolates belonging to the genus Pisolithus did not form typical ectomycorrhizas although a normal mantle was observed.

[Value of high-resolution computed tomography in evaluating cervical herniated disks]. / Intérêt de la tomodensitométrie à haute résolution dans l'évaluation des hernies discales cervicales.

Previous difficulties in the diagnosis of cervical disk hernia were related to lack of non-invasive imaging techniques, but the gap has now been filled by CT scan imaging. A total of 442 patients with pains in neck, shoulder or arm were referred for a CT scan to exclude a cervical disk hernia. Of the group studied, 2% were found to have a herniated disk, 16% a lateral hernia and 9% combined lateral hernia-narrow cervical canal due to concomitant arthrotic changes. Assessment of correlation between CT scan images and myelographic and surgical findings indicated that CT scan imaging is a very precise, non-invasive method for investigation of cervical disk hernia.