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Scientists Just Set A New Qubit Entanglement Record For Quantum Computers


Jonathan O'Callaghan

Senior Staff Writer

An arist's impression of the 20 entangled atoms in pairs (blue), triplets (pink), quadruplets (red), quintuplets (yellow). IQOQI Innsbruck/Harald Ritsch

Scientists say they have achieved a new record for quantum entanglement that could be a big boon for quantum computing.

Carried out by the Institute of Quantum Optics and Quantum Information (IQOQI) in Austria and published in Physical Review X, the research is based around something called qubits. These are quantum bits, which are the quantum equivalent of information bits used in computers.


Now, for the first time, the team has created a multi-particle entangled system that involves 20 qubits, which is a new record. What does that mean?

In this research, the team used laser light to entangle 20 calcium atoms in an ion trap experiment. This was done by first entangling the particles in pairs, and then observing the spread of entanglement to particle triplets, quadruplets, and quintuplets.

"We have chosen a MacGyver approach," the study’s lead author, Nicolai Friis from the IQOQI, said in a statement. "We had to find a way to detect multi-particle entanglement with a small number of feasible measurement settings."

Entanglement is the odd quirk of quantum mechanics in which two particles share a quantum state, even if they are separated by large distances. Although it’s usually used to describe pairs of particles, it can apply to groups as well.


The importance here is that the team were able to individually “see” each qubit, and they hope that the method could eventually lead to 50 entangled particles at once. This brings us closer to universal quantum communication, as it allows for more powerful quantum computation to take place.

“Since this is a good result showing that their 20 qubits actually do the things that qubits should do, it is really good to see,” Dr James Wootton, a quantum computation researcher from the University of Basel in Switzerland, told IFLScience.

“Generating large entangled states requires a fairly complex process, and it can be hard to do. So building and verifying ever bigger and fancier entangled states is an important way for us to benchmark progress in developing quantum hardware.”

Also noted is that this method uses trapped ions, a popular method for building quantum computers but one that’s seen as lagging behind superconducting qubits. Showing that this method works for high numbers will be a boon for trapped ion proponents, although there’s still a long way to go of course.


"We want to push the boundaries of our methods even further," the researchers noted in the statement. "By exploiting symmetries and focusing on certain observables, we can further optimize these methods to detect even more extensive multi-particle entanglement.”


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