This program, which funds equipment, was developed with the input of an engineer hired for 1.5 years by LANEF. Technical staff, scientists and academics from the CNRS and the UGA (> 20 contributors) contribute through the development of experimental set-ups and the supervision of students. About 130 Master students per year are given the opportunity to access set-ups for experiments on, for example, Josephson effect, second sound, Kinetic Inductance Detectors, indium superconductivity, helium latent heat, non-linear optics, Hall effect, optical tweezers and DNA nanostructures. New set-ups are being financed and operated through our program.
The students make a Superconducting/Insultaor/Superconducting Josephson junction.
The two superconducting parts are in Niobium (Tc ≈ 9 K) and the insulation is obtained by natural oxidation of this one. The experimental set-up is inserted into a reservoir of liquid helium (4.2 K) and allows the contact between the superconducting parts to be finely adjusted. The current-voltage characteristic of the junction and its dependence on a magnetic field and on a radiofrequency field (Squid effect, Shapiro steps) are measured.
Kinetic Inductance Detectors (KID) are superconducting resonators with a very high quality factor (Q ≈ 106)
These devices are the building blocks for photon detection for astrophysics or for reading quantum information. During this practical work, students study the influence of temperature on a KID resonator: regulation of a pumped helium bath cryostat, instrumentation of a temperature reader, measurement of resonances using a 'Vector Network Analyzer'.
Students size and prepare a cupronickel capillary tube, fitted with several thermometers and a heater.
This system is placed in a calorimeter and a circulation of liquid helium under controlled pressure is imposed in the capillary. The resistance is used to heat and possibly vaporize the Helium. The flow rate as well as the temperatures measured upstream and downstream make it possible to determine the specific heat and the latent heat of helium.
Students study of the linear and nonlinear optical properties of new anisotropic crystals.
The crystals are cut as cylinders polished on their edge, oriented by X-rays and placed onto a goniometric stage. The experiments are based on the use of a laser properly focused at the center of the cylinders so that the beam can propagate in all the directions of the cylinder plane. One part of experiments concerns the implementation of an experiment to study the linear optical properties relative to polarization of light, and propagation with the double refraction phenomenon. They are studied using a HeNe laser and a CCD camera. Another part deals the complete analysis of second harmonic generation and spontaneous down-conversion, were radiations wavelengths provided by a high power tunable laser are converted into other wavelengths in a nonlinear crystal cut as cylinder, and the angular distribution of the conversion efficiency is studied.
The students measure on an entangled two-particle state (Bell state or EPR state) which lead to a paradox interpreted as a proof of the incompleteness of the quantum theory.
For a Bell state, a measurement of the state of each particle taken individually gives a random outcome, but the two results are perfectly correlated. In other words, a measurement of the first particle state allows us to predict with certainty the state of the second one. For Einstein, Podolsky and Rosen, it implies that this state exists before the measurement, implying that there is a set of " hidden " variables not described by the theory that determine this state all along the experiment. John Bell showed that there were some cases where the two interpretations were leading to incompatible observations. This lab work aims to produce pairs of entangled photons and allows you to determine, with your own measurements, which theory can be invalidate.
Students prepare, connect and instrument a heating resistor and a thermal sensor
This experiment aims to measure the speed of the second sound in the superfluid phase of Helium (T ≤ 2.17 K). Students prepare, connect and instrument a heating resistor and a thermal sensor placed opposite at an adjustable distance. The resistance generates a wave of heat which is accompanied by a cross movement of normal fluid and superfluid. The thermometer detects the passage of the heat wave from which the speed of the second sound is deduced from the time of flight and the distance.
Students prepare and connect a sample of pure indium (Tc ≈ 3.4 K).
The sample is cooled in stages to temperatures close to 1.5 K. At each stage, the current-voltage characteristic of Indium is measured (up to critical currents of several tens of Amps). These characteristics make it possible to deduce the field-temperature phase diagram of Indium and to characterize the nature of this superconductor.
