Presentation of the lectures :
Thanks to recent advances, it is now possible to measure electromagnetic signals in the microwave range with an additional noise lower than one photon per mode.
Although the energy associated with a microwave photon is 100.000 times lower than an optical photon, and although detecting such a photon requires a circuit cooled to a temperature lower than 100 mK, it is much easier to control the spatial and temporal wave function of a photon at 5 GHz than at 500 THz.
Therefore, mesoscopic physics experiments, and more specifically those based on superconducting quantum circuits, are now seen as electronic transport as well as quantum optics (in which single photon detection has become "standard" during the last decades) experiments.
These lectures aim at showing the principles of new amplifiers that lie at the heart of mesoscopic measurements for which accuracy is only limited by the uncertainty principle.
The first part, based on the so-called "input-output" formalism, will treat in very details nonlinear and out-of-equilibrium effects that characterize active quantum circuits.
In particular, parametric amplifiers based on pumping one or several Josephson junctions will be considered. Links between gain, bandwidth, and dynamic range will illustrate the important role played by the quantum noise on the operation of these amplifiers and the associated signal processing performed by them.
Utilizing feedback towards controlling the dynamical state of a qubit will be seen in the last part of these lectures.
We will focus on an example, related to metrology, that aims at measuring persistent Rabi oscillations, which is a quantum phenomena predicted years ago but non demonstrated experimentally.
Associated seminars (on Tuesdays at 11:00 am, after the lectures):
- May 10: Fabien Portier (CEA-Saclay), "The Bright Side of Coulomb Blockade";
- May 17: Jan van Ruitenbeek (Leiden University, Pays-Bas), "Quantum Transport in Single-molecule Systems";
- Mai 24 : no lecture, nor seminar;
- May 31 : Irfan Siddiqi (UC Berkeley, USA): "Quantum Jumps of a Superconducting Artificial Atom";
- June 7: David DiVicenzo (IQI Aachen, Allemagne), "Quantum Error Correction and the Future of Solid State Qubits";
- June 14: Andrew Cleland (UC Santa Barbara, USA), "Images of Quantum Light" *;
- June 21: Benjamin Huard (LPA/ENS Paris), "Building a Quantum Limited Amplifier from Josephson Junctions and Resonators".
* Andrew Cleland will give another conference, "How to be in two places at the same time", on Tuesday 21 of June at 3:00 pm, in the same conference room.