Communications of the ACM
Quantum Computers Check Each Other’s Work
A new strategy utilizes quantum computers to verify solutions reached by other quantum computers.
Credit: Equinox Graphics
University of Vienna physicists have developed a strategy for verifying the solutions of quantum computers that relies on a blind quantum computing technique.
Quantum computers receive qubits and use them to perform tasks, although they are blind to input, output, and computations executed. The researchers used traps to test a computer's accuracy, involving short intermediate calculations for which the user already knows the solution.
"In case the quantum computer does not do its job properly, the trap delivers a result that differs from the expected one," says Vienna physicist Philip Walther, explaining that the traps enable users to determine when the quantum computer is inaccurate. He says their technique shows experimentally that quantum computers can verify one another's solutions, and theoretically that any size of quantum computer can be used to check another. Users can better ensure quantum computer accuracy by adding more traps to the system.
"The test is designed in such a way that the quantum computer cannot distinguish the trap from its normal tasks," Walther says. Although the experiments are currently in the proof of concept phase, "they're necessary first steps if we're ever going to have useful quantum computers," says Massachusetts Institute of Technology professor Scott Aaronson.
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