“Can one be convinced of the correctness of the computation of every quantum circuit, namely, every quantum experiment that can be conducted in the laboratory?” ask Dorit Aharonov and colleagues from the Hebrew University of Jerusalem in Israel.

That’s an interesting question of quantum computer science. If you can’t simulate the answer to calculation on a classical computer, how do you know the answer that a quantum computer arrives at is correct.

There’s a clue, says Aharanov, in Shor’s algorithm, which factors large numbers on a quantum computer. There is no way of knowing in advance whether the factors Shor’s algorithm finds are correct because that would be tantamount to the seemingly impossible task of  factoring numbers in polynomial time. But you can determine the veracity of the answer in retrospect simply by multiplying the factors together, which can be done easily on a classica lcomputer.

Aharanov and co use this as the model  for a new type of quantum proof that is analogous to the interactive proof systems used in classical computer science.

The group says the approach could be used to tackle a number of interesting problems in quantum computer science such as proving the performance of a quantum computer for a customer wishing to buy one for their own tasks.

That’ll be handy since clock cycles aren’t going to make the grade in the quantum computing age.

Ref: arxiv.org/abs/0810.5375: Interactive Proofs For Quantum Computations

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