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CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1465
DTSTART:20090323T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260506T181228Z
LAST-MODIFIED:20090325T124021Z
LOCATION:5310 Chamberlin
SUMMARY:Circuit QED<sup>2</sup>: Two amplifiers\, two resonators\, and
  two photons\, R. G. Herb Condensed Matter Seminar\, Matteo Mariantoni
 \, Walther-Meissner-Institut and Technical University
DESCRIPTION:In order to better understand the fundamental properties o
 f quantum  electrodynamics (QED)\, studying the zero-point fluctuation
 s of microwave  radiation represents an important task. In the first p
 art of this talk\, I present a full experimental characterization of t
 he microwave vacuum fluctuations via the Planck distribution of noise 
 at very low temperatures.  I show a detailed study of the cross-over f
 rom thermal noise to vacuum  quantum noise and quantify the vacuum flu
 ctuations level for a narrow frequency band centered around 6 GHz. I a
 lso demonstrate the change of the vacuum fluctuations level with the c
 arrier frequency. In addition\, I present a new type of heterodyne det
 ection particularly suitable for circuit QED systems. It is based on a
  microwave beam splitter and cross-correlation measurements and allows
  for a reconstruction of the entire covariance matrix of the vacuum fl
 uctuations. Finally\, I show that such a cross-correlation setup can b
 e used for detecting entanglement in a two-resonator circuit QED syste
 m.<br>
\n<br>
\nIn the second part of the talk\, I report on the obser
 vation of key signatures of a two-photon driven Jaynes-Cummings model\
 , which unveils the upconversion dynamics of a superconducting flux qu
 bit coupled to an on-chip resonator. The experimental results show a c
 lear evidence for the coexistence of one- and two-photon driven level 
 anticrossings of the qubit-resonator system. This results from the sym
 metry breaking of the system Hamiltonian\, when parity becomes a not w
 ell-defined property. This experiment provides deep insight into the i
 nterplay of multiphoton processes and symmetries in a qubit-resonator 
 system.
URL:https://www.physics.wisc.edu/events/?id=1465
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