title: Planck spectroscopy and quantum noise of microwave beam splitters.
abstract: We use a correlation function analysis of the field quadratures to characterize both the blackbody radiation emitted by a 50 Ω load resistor and the quantum properties of two types of beam splitters in the microwave regime. To this end, we first study vacuum fluctuations as a function of frequency in a Planck spectroscopy experiment and then measure the covariance matrix of weak thermal states. Our results provide direct experimental evidence that vacuum fluctuations represent the fundamental minimum quantum noise added by a beam splitter to any given input signal.
authors.affiliation: Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching, Germany. matmar@physics.ucsb.edu
authors.forename: M
authors.initials: M
authors.lastname: Mariantoni
authors.forename: E P
authors.initials: EP
authors.lastname: Menzel
authors.forename: F
authors.initials: F
authors.lastname: Deppe
authors.forename: M A
authors.initials: MA
authors.lastname: Araque Caballero
authors.forename: A
authors.initials: A
authors.lastname: Baust
authors.forename: T
authors.initials: T
authors.lastname: Niemczyk
authors.forename: E
authors.initials: E
authors.lastname: Hoffmann
authors.forename: E
authors.initials: E
authors.lastname: Solano
authors.forename: A
authors.initials: A
authors.lastname: Marx
authors.forename: R
authors.initials: R
authors.lastname: Gross