As a key technology in achieving the next generation of communications and computing technologies, quantum entanglement has been a topic of interest in the scientific community - with the latest efforts detailing how to achieve it through the application of heat.

An international team of researchers from Finland, China, Russia, and the USA - led by Aalto University members - demonstrated the use of temperature difference as a method for entangling pairs of electrons across superconducting materials. Scientists are now a step closer to advancing quantum devices with the new discovery, creating a new method for achieving entanglement. Details of their work are published in the journal Nature Communications, January 8.

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Quantum Entanglement: The Future of Computing

Led by Professor Pertti Hakonen from Aalto University in Finland, the new study demonstrates the use of thermoelectric effect - or the direct conversion of temperature differences to electric potential - in producing entangled electrons using an experimental setup.

"Quantum entanglement is the cornerstone of the novel quantum technologies," Hakonen explains in a statement. "This concept has puzzled many physicists over the years, including Albert Einstein, who worried a lot about the spooky interaction at a distance that it causes."

Entanglement is often described as a phenomenon wherein pairs or even groups of particles interact or get close enough with each other that their respective quantum states can no longer be described separately. This event is used in combining multiple quantum systems into a single one. In a computing context, it exponentially increases the total computational capacity of the system compared to their separate, non-entangled state.

"Entanglement can also be used in quantum cryptography, enabling the secure exchange of information over long distances," notes Professor Gordey Lesovik, a visiting professor at the Aalto University School of Science from the Moscow Institute of Physics in Russia. Methods for achieving entanglement efficiently and controllably is an important goal in quantum computing research.

Entangling Electrons Through the Thermoelectric Effect

In conducting the novel entanglement technique, researchers designed and fabricated an enclosure that contains an aluminum superconductor layered with graphene and superconducting metal electrodes. Superconductivity - or surfaces that allow electrons to pass through with virtually no resistance - is achieved with entangled electrons called "Cooper pairs." Also known as the BCS pair (for Bardeen-Cooper-Schrieffer pair), these electrons are basically bound together, mainly due to extremely low temperatures.

Then, by introducing a temperature difference on the superconductive surface, the electron pair is separated, and each of the electrons moves toward different metal electrodes. Researchers found out that even after the split, the electrons remain entangled despite being physically separated. In testing various materials for the experiment, researchers report that "particularly promising results" were observed using carbon nanotube, graphene, and nanowire materials.

Through this work, the international research team successfully demonstrated the use of thermal gradients (temperature difference) as a "prime mover" for generating entangled electrons in their experimental Cooper pair splitter. They also noted that their method is useful not only in quantum devices where an electrical input is neither desirable nor possible but also as a new platform for "realizing quantum thermodynamical experiments."


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