Quantum computers are evolving at a breakneck pace and are already pushing the limits of the world’s most powerful supercomputers.
However, these devices are particularly susceptible to external effects and hence prone to errors that can alter the computation’s outcome.
This is especially difficult for quantum computations that are beyond the capabilities of our trusted classical computers, as we can no longer independently check the findings via simulation.
To overcome this issue, the team devised and implemented a new cross-check technique that enables the results of one device’s calculation to be verified against the results of a related but fundamentally different calculation done on another device.
“We ask different quantum computers to perform different random-looking computations,” explains Martin Ringbauer from the University of Innsbruck.
“What the quantum computers don’t know is that there is a hidden connection between the computations they are doing.”
With the help of an alternative model of quantum computing built on graph structures, they were able to generate many different computations from a common source.
The scientists tested their approach on five existing quantum computers by combining four separate hardware technologies: superconducting circuits, trapped ions, photonics, and nuclear magnetic resonance.
“While the results may appear random and the computations are different, there are certain outputs that must agree if the devices are working correctly.”
This demonstrates that the strategy works on standard hardware without requiring any additional configuration. Additionally, the researchers showed how the technique may be used to validate a single device against itself.
Due to the fact that the two computations are so dissimilar, the two results will coincide only if they are also correct.
Another significant advantage of the new approach is that it eliminates the need for researchers to examine the entire output of the computation, which may be quite time-consuming.
According to the study authors, with the increasing availability of quantum computers, this technique may be critical for ensuring they perform as stated.
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