An unknown unitary gate, which is secretly chosen from several known ones, can always be distinguished perfectly. In this paper, we implement such a task on IBM’s quantum processor. More precisely, we experimentally demonstrate the discrimination of two qubit unitary gates, the identity gate and the 2 3 π-phase shift gate, using two discrimination schemes — the parallel scheme and the sequential scheme. We program these two schemes on the ibmqx4, a 5-qubit superconducting quantum processor via IBM cloud, with the help of the QSI modules. We report that both discrimination schemes achieve success probabilities at least 85%.
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Science China Information Sciences
Progress in quantum computing:Algorithms, communication, and applications
Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands

Liu, S., Li, Y., & Duan, R. (2019). Distinguishing unitary gates on the IBM quantum processor. Science China Information Sciences, 62. doi:10.1007/s11432-018-9703-y