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.
Abstract
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 [1]. 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.
[1] 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 [1], 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
[1] M.V. Gustafsson et al. Nature Physics, 8, 338 (2012)
Open to members of UoB only.
The Physics Colloquia are organised by and Rachel Holley.
