Quantum Computer Works Better Shut Off

waimate writes "A New Scientist article relates how its possible to get answers from a quantum computer even when your program isn't running." From the article: "With the right set-up, the theory suggested, the computer would sometimes get an answer out of the computer even though the program did not run. And now researchers from the University of Illinois at Urbana-Champaign have improved on the original design and built a non-running quantum computer that really works."

Comments

This is an old result

[Expert Determination]

I remember swapping a few emails with the author of a paper on this about ten years ago. Essentially you can get the result of the computation and yet the computer that runs destructively interferes with itself so that it essentially it remains unchanged at the end of the computation.

But this doesn't buy you anything. Quantum computers are reversible meaning they use no energy. And the computer has to spend just as long "doing nothing" as it would have spent doing the computation. And your computer is still tied up "doing nothing". So it's basically useless.