Super quick quantum random number generators enable “spooky action at a distance” between superconducting quantum bits

By May 16, 2023ICFO

The study, which relied on random number generators developed by the ICFO spin-off company Quside Technologies in collaboration with ICREA Professor at ICFO Morgan W. Mitchell, is published this month in Nature

ETHZ experimental setup in the lab at Zurich

Random number generators, developed by Quside Technologies in collaboration with ICREA Professor at ICFO Morgan W. Mitchell, have made possible a ground-breaking experiment published on May 10, 2023 in Nature. The experiment, in the laboratories of Andreas Wallraff at ETH Zurich, performed a “loophole-free Bell test,” similar to experiments that won the Nobel Prize in Physics last year. For the first time, the ETHZ experiment was able to perform this kind of experiment with superconducting quantum bits, the basis for today’s most advanced quantum computers. The results show “spooky action at a distance,” in which objects in different places behave as if they were a single system.

As described by the group at ETHZ, the ETHZ experiment first “entangled” two superconducting qubits at temperatures near absolute zero and separated by 30 meters of distance. The team then measured the state of the qubits simultaneously, and observed that the state of one qubit usually agreed with the state of the other qubit, a coordinated response consistent with “spooky action at a distance.” To be sure this coordination was not due to ordinary signals traveling from one qubit to the other, the ETHZ team chose randomly which type of measurements to make on the qubits, and they made the measurements so quickly that not even a signal at the speed of light could reach the other qubit in time.

This feat required extremely fast random number generators, and for this the ETHZ team turned to Quside and Prof. Mitchell’s research group at ICFO to develop a random number generator with unprecedented speed. Quside adapted their patented quantum random number generation technology, combining a novel parallel architecture with an extremely fast “randomness extraction” stage. In this way, the QRNG devices delivered pure random bits in 17 nanoseconds, the time it takes light to travel five meters. “ETHZ asked us to go beyond the state of the art in random number generation. Never before has an experiment required such good random numbers in such a short time. The Quside team did an amazing job to engineer the solution and integrate it with the ETHZ experiment.” Says Carlos Abellán, CEO of Quside and a co-author of the ETHZ study.

The experiment confirms that quantum mechanics allows for non-local correlations, which means that superconducting circuits can be entangled over a comparatively large distance. This may enable new methods of secure communications.

For the Quside/ICFO team, the participation in the ETHZ experiment is not just a chance to contribute to fundamental physics. As Prof. Mitchell says, “This experiment pushed us to develop technologies that we now apply to communications security and high-performance computing, which also require fast, high-quality random numbers.”

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