Scientists couple magnetization to superconductivity for quantum discoveries

Scientists couple magnetization to superconductivity for quantum discoveries
Researchers at Argonne have demonstrated an on-chip quantum circuit and realized strong coupling between a superconducting resonator and a magnetic device. The results introduce a new platform for investigating on-chip quantum magnonics and quantum information processing. Credit: Ellen Weiss / Argonne National Laboratory

Quantum computing promises to revolutionize the ways in which scientists can process and manipulate information. The physical and material underpinnings for quantum technologies are still being explored, and researchers continue to look for new ways in which information can be manipulated and exchanged at the quantum level.

In a recent study, scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have created a miniaturized chip-based superconducting circuit that couples quantum waves of magnetic spins called magnons to photons of equivalent energy. Through the development of this "on chip" approach that marries magnetism and superconductivity for manipulation of quantum information, this fundamental discovery could help to lay the foundation for future advancements in quantum computing.

Magnons emerge in magnetically ordered systems as excitations within a that cause an oscillation of the magnetization directions at each atom in the material—a phenomenon called a spin wave. "You can think of it like having an array of compass needles that are all magnetically linked together," said Argonne materials scientist Valentine Novosad, an author of the study. "If you kick one in a particular direction, it will cause a wave that propagates through the rest."

Just as photons of light can be thought of as both waves and particles, so too can magnons. "The electromagnetic wave represented by a is equivalent to the spin wave represented by a —the two are analogues of each other," said Argonne postdoctoral researcher Yi Li, another author of the study.

Because photons and magnons share such a close relationship to each other, and both contain a magnetic field component, the Argonne scientists sought a way to couple the two together. The magnons and photons "talk" to each other through a superconducting microwave cavity, which carries microwave photons with an energy identical to the energy of magnons in the magnetic systems that could be paired to it.

Using a superconducting resonator with a coplanar geometry proved effective because it allowed the researchers to transmit a microwave current with low loss. Additionally, it also allowed them to conveniently define the frequency of photons for coupling to the magnons.

"By pairing the right length of resonator with the right energy of our magnons and photons, we are in essence creating a kind of echo chamber for energy and quantum information," Novosad said. "The excitations stay in the resonator for a much longer length of time, and when it comes to doing quantum computing, those are the precious moments during which we can perform operations."

Because the dimensions of the resonator determine the frequency of the microwave photon, magnetic fields are required to tune the magnon to match it.

"You can think of it like tuning a guitar or a violin," Novosad said. "The length of your string—in this case, our resonator of photons—is fixed. Independently, for the magnons, we can tune the instrument by adjusting the applied , which is similar to modifying the amount of tension on the string."

Ultimately, Li said, the combination of a superconducting and a magnetic system allows for precise coupling and decoupling of the magnon and photon, presenting opportunities for manipulating quantum information.

Argonne's Center for Nanoscale Materials, a DOE Office of Science User Facility, was used to lithographically process the resonator.

A paper based on the study, "Strong coupling between magnons and microwave photons in on-chip ferromagnet-superconductor thin-film devices," appeared in the Sept. 3 issue of Physical Review Letters and was also highlighted in the Editors' Suggestion.

Explore further

Studying quantum phenomena in magnetic systems to understand exotic states of matter

More information: Yi Li et al. Strong Coupling between Magnons and Microwave Photons in On-Chip Ferromagnet-Superconductor Thin-Film Devices, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.107701
Journal information: Physical Review Letters

Citation: Scientists couple magnetization to superconductivity for quantum discoveries (2019, September 6) retrieved 19 October 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Sep 06, 2019
Bose–Einstein condensate

but all this research
use's a Bose-Einstein condensate
fore this state of matter
occurs at very low temperatures 0.1 to 0.9Kelvin
fore it will be a while for high temperature superconducting at 1 or 2Kelvin
as to room temperature superconducting....
when it comes, this research will have its use's, as no one is carrying liquid nitrogen tanks around

Sep 06, 2019
Nonce and lo, wherefore art hast thou yon pemmiken larder foresook thee? Wot?

Sep 07, 2019
Quantum Waves of Magnetic Spins called Magnons

Topological Dirac magnons spotted for the first time at zero magnetic field
The discovery of this 2D material
acts as a magnetic topological insulator
in the absence of an external magnetic field
The material is chromium triiodide
its magnetic properties
characterized by analysing spin oscillations that were induced by neutron scattering

When atoms inside a 2D material are arranged in certain patterns
their constituent electrons
can display a fascinating range of behaviours
not usually seen in everyday materials
Within the 2D honeycomb lattice of graphene
for example, so-called "Dirac electrons"
can move at relativistic speed
and behave much like photons with zero mass

A magnon is a quasiparticle
A quasiparticle is a quantum of energy in a crystal lattice
Has momentum, position and regarded as a particle

For a Magnon is a energy

Sep 07, 2019
Magnons and Quasiparticles

An electron travels through a semiconductor
Its motion is disturbed in a complex way
By its interactions with all of the other electrons and nuclei
It approximately behaves like an electron
With a different mass
Travelling unperturbed through free space
This "electron with a different mass"
Is called an "electron quasiparticle"

In this Alice in Wonderland of quantum particles, spin, waves and magnons
All is not what it seems
Fore this energy of waves is massless
Despite these quasiparticle electron effects
Quasiparticles do not actually exist; fore they simply consist of energy!

Sep 07, 2019
This is this Hidden Trail: In this Trail of Descriptives

A particle is an object ascribed several physical properties, chemical, volume, density and mass
A magnon is a quasiparticle
A quasiparticle is a quantum of energy
A quasiparticle is regarded as a particle
A particle is an object of mass

p.s. fore we have just lost this plot yet again, as this quasiparticle, is this massless energy, meaning the descriptive "quasiparticle" is not the quasiparticle it purports to be, as a particle is a massive body!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more