Parametric Amplification of Quantum Signals with Superconducting Tunnel Junction Circuits
Abstract: Quantum Mechanics puts a limit on how small the degradation of information passing through an amplifier can be. It is known theoretically that the minimum noise added to the signal by an amplifier, operating in the usual in phase preserving mode, amounts to at least half a photon at the signal frequency. Is it possible to construct an amplifier working at microwave frequencies that would reach this quantum limit and still be practical in terms of gain, bandwidth and dynamical range? We will present recent work by our group answering positively this question, which is of crucial importance for the readout of solid state qubits, and more generally, for measurements of very weak electromagnetic signals in various areas of science.