Poor Schrödinger’s cat: Entangled particles can now be in 103 states at once

Quantum computers, which could bring about a new age of ultra-fast, low-power computing, draw their power from networks of particles. Like transistors in a modern computer, scientists have focused on working with more and more particles to boost their speed. But researchers at the Autonomous University of Barcelona asked a different question: What if they pushed each particle to do more, instead of relying on more particles?

The result is a system that relies on just two particles, but each of the particles can assume 103 different states. Generally, particles in quantum computers can be in three different states, such as “up,” “down” or “both.” It’s like Schrödinger’s cat, a thought experiment that poses a cat locked in a box with poison is both alive and dead until an observer opens the box.

“We have two Schrödinger cats which could be alive, dead, or in 101 other states simultaneously” UAB researcher Marcus Huber said in a release. “The discovery could facilitate the experimental development of quantum computers, since this would be an easier way of obtaining high dimensions of entanglement with few particles.”

Entanglement refers to the unique state particles enter in a quantum system. If you alter one particle, it affects the others, even if they are physically separated. Scientists have been able to entangle up to 14 particles at a time. But the more particles they add, the more unstable and difficult to maintain the system becomes.

Using particles that can be in more than three states means researchers can get the same amount of computing power out of fewer particles. Previously, researchers had measured particles in up to 11 states. Reaching 103 just meant measuring more of a particle’s characteristics, such as speed and direction.

The Autonomous University of Barcelona team is now working on controlling which state the particles enter, which is a necessary step before the system could be used in a quantum computer.