Reverse Checking of Quantum Algorithm Execution

Verification of quantum computation is critical because undesirable interference and noise are major technical hurdles in quantum computing. We propose an approach for reverse checking of computation results that takes advantage of quantum teleportation and reversibility of unitary quantum gates. The main idea is to preserve the quantum state after the computation ends and before the result is measured, so that quantum teleportation can be performed to “save” the quantum state before the readout. After that, the computation is reversely performed in the reverse order of gate operations. The end result should match the original input. Any discrepancy would be proof of errors during computation or verification. The advantage of this approach is that the reverse computation circuit can be automatically generated and performed and that the error rate obtained reflects what happened during the actual computation. In addition, this approach leads to a potential way to reduce error rates in the future by discarding results from individual shots of the execution with detected errors.