Long-range quantum entanglement requires three-way interaction

Infographic explaining the experiment. 1 credit

A theoretical study shows that long-range entanglement can indeed survive temperatures above absolute zero, if the correct conditions are met.

Quantum computing has been heralded as the next revolutionary step in computing. However, current systems are only practically stable at temperatures close to absolute zero. A new theorem from a Japanese research collaboration provides insight into which types of long-range quantum entanglement survive non-zero temperatures, revealing a fundamental aspect of macroscopic quantum phenomena and paving the way to a better understanding of quantum systems.

When things get small, down to the scale of a thousandth of the width of a human hair, the laws of classical physics are replaced by those of quantum physics. The quantum world is weird and wonderful, and there’s a lot about it that scientists have yet to figure out. Large-scale or “macroscopic” quantum effects play a key role in extraordinary phenomena such as superconductivity, which may be a game-changer in future energy transport, as well as for the continued development of quantum computers.

It is possible to observe and measure “quantity” at this scale in particular systems using long-range quantum entanglement. Quantum entanglement, which Albert Einstein described as “frightening action at a distance,” occurs when a group of particles cannot be described independently of each other. This means that their properties are linked: if you can completely describe a particle, you will also know everything about the particles with which it is entangled.

Long-range entanglement is at the heart of quantum information theory, and its better understanding could lead to a breakthrough in quantum computing technologies. However, long-range quantum entanglement is stable under specific conditions, such as between three or more parties and at temperatures near absolute zero. What happens to two-part entangled systems at non-zero temperatures? To answer this question, researchers from the RIKEN Center for Advanced Intelligence Project, Tokyo, and Keio University, Yokohama, recently presented a theoretical study on Physical examination X describing long-range entanglement at temperatures above absolute zero in bipartite systems.

“The aim of our study was to identify a limitation of the long-range entanglement structure at arbitrary non-zero temperatures,” says RIKEN Hakubi team leader Tomotaka Kuwahara, one of the authors of the study, who carried out the research while at the RIKEN Center for Advanced Intelligence Project. “We provide simple prohibition theorems that show what types of long-range entanglement can survive non-zero temperatures. At temperatures above absolute zero, particles of a material vibrate and move due to the thermal energy, which acts against quantum entanglement. At arbitrary nonzero temperatures, no long-range entanglement can persist between just two subsystems.”

The researchers’ findings are consistent with previous observations that long-range entanglement only survives at non-zero temperature when more than three subsystems are involved. The results suggest that this is a fundamental aspect of macroscopic quantum phenomena at room temperature, and that quantum devices should be designed to have multipartite entangled states.

“This result has opened the door to a deeper understanding of quantum entanglement over large distances, so this is just the beginning,” says Professor Keijo Saito of Keio University, co-author of the study. . “We aim to deepen our understanding of the relationship between quantum entanglement and temperature in the future. This knowledge will trigger and stimulate the development of future quantum devices that operate at room temperature, making them practical.”

While quantum devices that operate at stable ambient temperatures are still in their infancy, quantum entanglement looks poised to “bind” the future of this field.

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More information:
Tomotaka Kuwahara et al, Exponential clustering of bipartite quantum entanglement at arbitrary temperatures, Physical examination X (2022). DOI: 10.1103/PhysRevX.12.021022

Quote: It Takes Three To Tangle: Long-Range Quantum Entanglement Requires Three-Way Interaction (2022, May 6) Retrieved May 6, 2022, from https://phys.org/news/2022-05-tangle -long-range-quantum-entanglement-three-way.html

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