Lecturer: Mr. Shlomi Matityahu
Affiliation: Ben-Gurion University of the Negev
Abstract:
The low-temperature physics of amorphous
and disordered solids has been a subject of
great interest for more than four decades.
Below about 1K the acoustic and
thermodynamic properties of a large variety of
glasses are not only qualitatively different
compared to their crystalline counterparts, but
also show a remarkable degree of universality.
This universal behavior was explained by the
existence of low-energy excitations with two-
level structure, known as tunneling two-level
systems (TLSs).
Recent progress with microfabricated quantum
devices has revealed that an ubiquitous source
of noise originates in such TLSs.
In this talk I will describe how individual TLSs
in the Jospehson junction of a superconducting
qubit can be probed and manipulated, and
discuss a recent experiment in which Ramsey
and spin-echo dephasing rates of individual
TLSs were measured. I will show that most
features of the Ramsey dephasing can be
understood within the standard model of
tunneling TLSs, whereas the spin-echo
dephasing rate suggests the existence of some
white noise environment. I will discuss a two-
TLS model as a possible explanation for such
an environment.