title: Detection of quantum noise from an electrically driven two-level system.
abstract: The electrical noise of mesoscopic devices can be strongly influenced by the quantum motion of electrons. To probe this effect, we have measured the current fluctuations at high frequency (5 to 90 gigahertz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device, we can measure the high-frequency, nonsymmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.
authors.affiliation: Department of Nanoscience and ERATO Mesoscopic Correlation Project, Delft University of Technology, Post Office Box 5046, 2600 GA Delft, Netherlands. deblock@ps.u-psud.fr
authors.forename: Richard
authors.initials: R
authors.lastname: Deblock
authors.forename: Eugen
authors.initials: E
authors.lastname: Onac
authors.forename: Leonid
authors.initials: L
authors.lastname: Gurevich
authors.forename: Leo P
authors.initials: LP
authors.lastname: Kouwenhoven