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Quantum entanglement of electrons using heat

Entanglement of electrons with heat

Image of a fake electron microscope on the sample, the green layers are graphene on the gray superconductor. Blue metal electrodes are used to extract entangled electrons. Credit: Aalto University

Quantum entanglement is key to next-generation computing and communication technology, and Aalto researchers can now produce it using temperature differences.

A joint group of scientists from Finland, Russia, China and the United States has demonstrated that the temperature difference can be used to entangle electron pairs in superconducting structures. The experimental discovery, published in Nature Communications, promises powerful applications in quantum devices, which brings us one step closer to the applications of the second quantum revolution.

The team, led by Professor Perth Hakonen of Aalto University, showed that the thermoelectric effect provides a new method for producing entangled electrons in a new device. “Quantum entanglement is the cornerstone of new quantum technologies. However, this concept has puzzled many physicists over the years, including Albert Einstein, who was very concerned about the ghostly distance interactions it caused, ”says Prof. Hakonen.

IN quantum calculations, entanglement is used to merge individual quantum systems into one, which exponentially increases their total computational capacity. “Entanglement can also be used in quantum cryptography, which allows secure exchange of information over long distances,”

; explains Prof. Gordey Lesovik of the Moscow Institute of Physics and Technology, who has served several times as a visiting professor at Aalto Nauka University School. Given the importance of entanglement for quantum technology, the ability to easily and controlledly create entanglement is an important goal for researchers.

Researchers have designed a device where a superconductor is layered graphene and metal electrodes. “Superconductivity is caused by tangled pairs of electrons called Cooper pairs.” Using a temperature difference, we make them separate, and each electron then moves to a different normal metal electrode, ”explains PhD student Nikita Kirsanov from Aalto University. “The resulting electrons remain entangled, although they are separated by fairly large distances.”

Along with the practical consequences, the work is of considerable fundamental importance. The experiment showed that the Cooper pair separation process works as a mechanism for converting the temperature difference into correlated electrical signals into superconducting structures. The developed experimental scheme can also become a platform for original quantum thermodynamic experiments.

Reference: “Thermoelectric current in a graphene cooper splitter” by ZB Tan, A. Laitinen, NS Kirsanov, A. Galda, VM Vinokur, M. Haque, A. Savin, DS Golubev, GB Lesovik and PJ Hakonen, 8 January 2021, Nature Communications.
DOI: 10.1038 / s41467-020-20476-7

The work was carried out with the help of the OtaNano research infrastructure. OtaNano provides a modern working environment and equipment for nanosciences and technologies and quantum technology research in Finland. OtaNano is managed by Aalto University and VTT and is available to academic and commercial users internationally. To learn more, visit their website. The work was supported by QTF-funded (Academy of Finland CoE). Gordey Lesovik’s visiting faculty funding comes from Aalto University School of Science, and Jenbin Tan’s postgraduate scholarship from the Finnish Academy.

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