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By coupling magnetic behavior to a superconducting circuit, Argonne scientists are opening the way to quantum information systems.
Quantum computing promises to revolutionize the way scientists can process and manipulate information. The physical and material foundations of quantum technologies are still under study and researchers continue to search for new ways to manipulate and exchange information at the quantum level.
In a recent study, scientists at the Argonne National Laboratory of the US Department of Energy created a superconducting circuit based on miniaturized chips that couples the quantum waves of magnetic spins called magnons to photons of equivalent energy. Through the development of this "on-chip" approach that combines magnetism and superconductivity for the manipulation of quantum information, this fundamental discovery could help lay the foundation for future progress in quantum computing.
"By associating the good length of resonator with the good energy of our magnons and photons, we are essentially creating a kind of echo chamber for energy and quantum information," said Valentine Novosad. scientist in materials from the Argonne.
The magnons emerge in ordered magnetic systems in the form of excitations in a magnetic material that cause oscillation of the magnetization directions at each atom in the material – a phenomenon called a spin wave. "You can think of this as a set of compass needles that are all magnetically related," said Valentine Novosad, a materials scientist from Argonne, author of the study. "If you kick in one direction, it will cause a wave that spreads through the rest."
Light photons can be considered as both waves and particles, but magnons too. "The electromagnetic wave represented by a photon is equivalent to the spin wave represented by a magnon – both are analogues of one another," said the postdoctoral researcher. Argonne, Yi Li, another author of the study.
Since photons and magnons are very close to each other and both contain a magnetic field component, Argonne scientists have sought a way to couple the two. Magnons and photons "talk to each other" through a microwave superconducting cavity, which carries microwave photons of the same energy as magnons in magnetic systems. can be coupled.
The use of a superconducting resonator with coplanar geometry has been shown to be effective as it allowed researchers to transmit a microwave current with a low loss. In addition, it also allowed them to easily define the frequency of the photons to be coupled to the magnons.
"By associating the right length of resonator with the good energy of our magnons and photons, we are essentially creating a kind of echo chamber for energy and quantum information," Novosad said. "The excitations stay in the resonator for a much longer time, and when it comes to doing quantum computing, these are the precious moments during which we can perform operations."
Since the resonator dimensions determine the frequency of the microwave photon, magnetic fields are needed to tune the magnon accordingly.
"You can think of it as tuning a guitar or a violin," Novosad said. "The length of your chain – in this case, our photon resonator – is fixed. Regardless, for magnons, we can tune the instrument by adjusting the applied magnetic field, which amounts to altering the intensity of the tension on the string. "
In the end, the binding of a superconducting system and a magnetic system allows a precise coupling and decoupling of the magnon and the photon, thus offering possibilities of manipulation of the quantum information.
The Argonne Center for Materials at the Nanometer Scale, a user facility from DOE 's Office of Science, was used to process the resonator by lithography.
An article based on the study entitled "Strong coupling of microwave photons and microwave photons in ferromagnetic-superconducting thin film devices on chips" was published in the September 3, 2019 issue: Letters of physical examination and was also highlighted in the editors' suggestion. DOI: 10.1103 / PhysRevLett.123.107701
Yong-Lei Wang from Argonne, Jing Xu, Sergi Lendinez, Zhizhi Zhang, Junjia Ding, Trupti Khaire, Hilal Saglam, Ralu Divan, John Pearson, Wai-Kwong Kwok, Zhili Xiao, Axel Hoffmann, and Wei Zhang. Yi Li and Wei Zhang are also affiliated with the University of Oakland.
The research was funded by the DOE Bureau of Science (Office of Basic Energy Science).
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