Demonstration of a Tunable Coupler Suitable for Investigating Ultra-strong Coupling Light-matter Interactions in Superconducting Devices
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Date
2022-05-02
Authors
Janzen, Noah
Journal Title
Journal ISSN
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Publisher
University of Waterloo
Abstract
One of the most ubiquitous processes in nature is the interaction of matter and an
electromagnetic field which is well described using the spin-boson model. These light-
matter interactions are specified by an interaction strength which is nominally fixed by
nature. However, superconducting circuits are able to devise systems using microfabricated
quantum devices to increase the dimensionless coupling strength α. The coupling strength
is defined as α = Γ01/π∆ where Γ01 is the decay rate and ∆ is the transition frequency of
the system. As the strength increases and the rate of interaction approaches the frequency
of the system, the light-matter interactions enter the ultra-strong coupling (USC) regime
where α ∼ 0.1. Approximations that are often made to simplify the spin-boson model begin
to break down in the USC regime making the analysis of these systems challenging. We
demonstrate a flux tunable coupler with potential to explore these dynamics by coupling
a persistent current qubit (PCQ) as artificial atom to an open transmission line (TL)
as source of continuous bosonic modes. The tunable coupler is able to both decouple
the PCQ from the TL as well as enable the USC regime of interactions with a coupling
range spanning from αmin = 2.4 × 10−4 to αmax = 1.2 × 10−1. The future objective is to
directly explore the time-domain properties of the USC regime and to open new research
approaches to relativistic quantum information (RQI) by using the tunable coupler as a
switching function.
Description
Keywords
ultra-strong coupling, relativistic quantum information, light-matter interaction, flux qubit, superconducting circuit, tunable coupler