Speaker
Prof.
Per Delsing
(Chalmers University of Technology, Sweden)
Description
Abstract: Mechanical movement can be quantized in the
same way as light, into particles of vibration known as
phonons. Recent experiments have shown that quantum
information generated in qubits can be converted to
vibrations in mechanical resonators, which resemble
miniature drum skins or piano strings. Such resonators
restrict motion to their discrete and stationary modes, and
thus serve as local storage units for phonons. Here, we
demonstrate the use of phonons as propagating carriers of
quantum information, by coupling them strongly to a
superconducting qubit. The phonons thus serve the same
role as itinerant photons have in the field of quantum
optics. Three different experiments are presented: i)
Exciting the qubit with an electromagnetic signal we can
“listen” to the SAW phonons emitted by the qubit. The low
speed of sound also allows us to observe the emission of the
qubit in the time domain, giving clear proof that the
dominant coupling is acoustic. ii) Reflecting a SAW wave off
the qubit, we observe a nonlinear reflection with strong
reflection at low power and low reflection at high power. iii)
Exciting the qubit with both an electromagnetic signal and
with a SAW signal, we can do two tone spectroscopy on the
qubit. Due to the low speed of sound and a potential for
very strong coupling, the use of propagating phonons as
quantum carriers allows regimes to be explored, which are
difficult or impossible to reach with photons. This work was
done in collaboration with M.V. Gustafsson, T. Aref, A. Frisk-
Kockum, M.K. Ekström, and G. Johansson.
