18 March 2013, 4 pm
Will talk on two topics: 'The dynamical Casimir effect & Local probing of propagating acoustic waves in a gigahertz echo chamber.'
Powell Lecture Theatre, H H Wills Physics Laboratory.
Dynamical Casimir effect: We have been able to observe the Dynamical Casimir Effect (DCE) in a superconducting circuit consisting of a coplanar transmission line with a tunable electrical length . The rate of change of the electrical length can be made very fast (a substantial fraction of the speed of light) by modulating the inductance of a superconducting quantum interference device at high frequencies (~10 GHz). In addition to observing the creation of real photons, we detect two-mode squeezing in the emitted radiation, which is a signature of the quantum character of the generation process. This phenomenon was predicted 40 years ago and has not been observed until now.
 C.M. Wilson et al. Nature, 479, 376 (2011).
Local probing of propagating acoustic waves in a gigahertz echo chamber: In the same way that micro-mechanical resonators resemble guitar strings and drums, surface acoustic waves resemble the sound these instruments produce, but moving over a solid surface rather than through air. In contrast with oscillations in suspended resonators, such propagating mechanical waves have not before been studied near the quantum mechanical limits. In a recent paper , we have demonstrated local probing of surface acoustic waves with a displacement sensitivity of 30 am_RMS/√Hz and detection sensitivity on the single-phonon level after averaging, at a frequency of 932 MHz. Our probe is a piezoelectrically coupled single-electron transistor, which is sufficiently fast, non-destructive and localized to enable us to track pulses echoing back and forth in a long acoustic cavity, self-interfering and ringing the cavity up and down. Prospects include quantum investigations of phonon–phonon interactions, and acoustic coupling to superconducting qubits
 M.V. Gustafsson et al. Nature Physics, 8, 338 (2012)
Open to members of UoB only.
The Physics Colloquia are organised byand Rachel Holley.