How to force photons to never bounce back

Date:
October 13, 2021
Source:
Ecole Polytechnique Fe'de'rale de Lausanne
Summary:
Scientists have developed a topology-based method that forces
microwave photons to travel along on way path, despite unprecedented
levels of disorder and obstacles on their way. This discovery
paves the way to a new generation of high-frequency circuits and
extremely robust, compact communication devices.



FULL STORY ========================================================================== Topological insulators are materials whose structure forces photons
and electrons to move only along the material's boundary and only in
one direction.

These particles experience very little resistance and travel freely
past obstacles such as impurities, fabrication defects, a change of
signal's trajectory within a circuit, or objects placed intentionally in
the particles' path. That's because these particles, instead of being
reflected by the obstacle, go around it "like river-water flowing past
a rock," says Prof.

Romain Fleury, head of EPFL's Laboratory of Wave Engineering, within
the School of Engineering.


========================================================================== Until now, these particles' exceptional resilience to obstacles applied
only to limited perturbations in the material, meaning this property
couldn't be exploited widely in photonics-based applications. However,
that could soon change thanks to research being conducted by Prof. Fleury
along with his PhD student Zhe Zhang and Pierre Delplace from the ENS
Lyon Physics Laboratory.

Their study, appearing in the journal Nature, introduces a topological insulator in which the transmission of microwave photons can survive unprecedented levels of disorder.

"We were able to create a rare topological phase that can be characterized
as an anomalous topological insulator. This phase arises from the
mathematical properties of unitary groups and gives the material unique --
and unexpected - - transmission properties," says Zhang.

This discovery holds great promise for new advances in science and
technology.

"When engineers design hyperfrequency circuits, they have to be very
careful to make sure that waves are not reflected but rather guided along
a given path and through a series of components. That's the first thing
I teach my electrical engineering students," says Prof. Fleury. "This
intrinsic constraint, known as impedance matching, limits our ability
to manipulate wave signals. However, with our discovery, we can take
a completely different approach, by using topology to build circuits
and devices without having to worry about impedance matching --
a factor that currently restricts the scope of modern technology."
Prof. Fleury's lab is now working on concrete applications for their
new topological insulator. "These types of topological circuits could be extremely useful for developing next-generation communication systems,"
he says. "Such systems require circuits that are highly reliable and
easily reconfigurable." His research group is also looking at how the discovery could be used for developing new kinds of photonic processors
and quantum computers.

========================================================================== Story Source: Materials provided by
Ecole_Polytechnique_Fe'de'rale_de_Lausanne. Original written by Florent
Hiard. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zhe Zhang, Pierre Delplace and Romain Fleury. Superior robustness of
anomalous non-reciprocal topological edge states. Nature, 2021 DOI:
10.1038/s41586-021-03868-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211013114012.htm

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