Detecting Temporal Correlation via Quantum Random Number Generation
This addresses a critical issue for quantum computing reliability, as temporal correlation can undermine the randomness and correctness of quantum computations, though it is incremental in identifying a specific error source.
The researchers tackled the problem of temporal correlation in outputs from a 20-qubit superconducting quantum computer, finding that some sequences exhibited such correlation unrelated to qubit relaxation times, indicating a potential systematic error.
All computing devices, including quantum computers, must exhibit that for a given input, an output is produced in accordance with the program. The outputs generated by quantum computers that fulfill these requirements are not temporally correlated, however. In a quantum-computing device comprising solid-state qubits such as superconducting qubits, any operation to rest the qubits to their initial state faces a practical problem. We applied a statistical analysis to a collection of random numbers output from a 20-qubit superconducting-qubit cloud quantum computer using the simplest random number generation scheme. The analysis indicates temporal correlation in the output of some sequences obtained from the 20 qubits. This temporal correlation is not related to the relaxation time of each qubit. We conclude that the correlation could be a result of a systematic error.