Carlos González-Ballestero (Institute of theoretical physics – U Insbruck)

Despite its tremendous success, microwave-based quantum technology has limitations that could
be solved by a hybrid approach, i. e. by interfacing microwaves with another degree of freedom
with complementary properties. Spin waves in ferromagnets, and their quanta magnons, are ideal
candidates as they show tuneable spectrum and nonlinearity, have sub-micron wavelengths at
microwave frequencies, and couple efficiently to multiple other degrees of freedom. These
properties have resulted in the development of advanced classical spin wave-based nanodevices
for information processing. Bringing these devices to the quantum regime would provide a
flexible & technology-ready complement for microwave quantum technology. So far, however, no
experiment has shown quantum behavior of spin waves in nanodevices. One of the major
bottlenecks is the lack of theoretical models able to describe these complex excitations in
In this talk I will share our approach to this challenge: nanophotonics-inspired magnonics. First, I
will introduce spin waves and the current challenges toward quantum magnonic nanodevices.
Then, I will overview our theoretical work aimed at reaching this goal. I will show how inverse
design enables to engineer coherent classical spin wave pulses in nanostructures, and how the
propagation of spin waves can be coherently and dynamically manipulated using ensembles of
solid-state spins. Our work is the first step toward bridging the gap between classical magnonics
and quantum optics and allow hybrid quantum technologies based on magnons.