Abstract
We use a correlation function analysis of the field quadratures to characterize both the blackbody radiation emitted by a 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.
- Received 16 March 2010
DOI:https://doi.org/10.1103/PhysRevLett.105.133601
© 2010 The American Physical Society