Quantum entanglement of electrons using heat

False-color electron microscope image of the sample, the green layers being graphene on top of the gray superconductor. Blue metal electrodes are used to extract entangled electrons. Credit: Aalto University

Quantum entanglement is key to the next generation of computing and communications technology, and Aalto researchers can now reproduce it using temperature differences.

A joint group of scientists from Finland, Russia, China and the USA demonstrated that temperature differences can be used to intertwine pairs of electrons in superconducting structures. An experimental discovery published in Nature CommunicationsIt promises powerful applications in quantum devices, bringing us one step closer to applications of the second quantum revolution.

The team, led by Professor Bertie Haakonen of Aalto University, showed that the thermoelectric effect provides a new way to produce 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 frightening interaction it causes,” says Professor Haakonen.

at Quantitative Statistics, Entanglement is used to combine individual quantum systems into a single system, which greatly increases their overall computational capacity. “Entanglement can also be used in quantum coding, enabling the secure exchange of information over long distances,” explains Professor Gordy Lesovik of the Moscow Institute of Physics and Technology, who has worked several times as a visiting professor at Aalto University College. Given the importance of entanglement in quantum technology, the ability to create easily and manageable entanglement is an important goal for researchers.

The researchers designed a device in which the superconductor layer is separated Graphene And metal electrodes. “Superconductivity is the result of entangled pairs of electrons called“ Cooper pairs. ”PhD candidate Nikita Kirsanov, from Aalto University, explains,“ By using different temperatures, we cause them to split, as each electron then moves to a different normal metal electrode. ”They remain. The resulting electrons are entangled despite being separated over very long distances. ”

Besides the practical implications, the work is of great fundamental importance. Experience has shown that the Cooper pair splitting process acts as a mechanism for converting temperature differences into interconnected electrical signals in superconducting structures. The developed experimental scheme could also become the platform for original quantum thermodynamic experiments.

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

The work was carried out using the OtaNano research infrastructure. OtaNano provides a modern working environment and equipment for research in nanoscience and nanotechnology and quantum technologies in Finland. OtaNano is powered by Aalto University and VTT, and is available to both academic and business users internationally. To find out more, visit their website. The work was supported by funding from QTF (CoE Academy of Finland). The funding for the visiting professor for Jordi Lesovic came from Aalto University’s Faculty of Science, and the Zhenbing Tan Postdoctoral Scholarship came from the Academy of Finland.