Near-Optimal Parallel Unitary Process Tomography in Diamond Distance

Abstract:Unitary process tomography is the act of learning how an unknown unitary gate acts on a quantum system. It is an essential procedure for realizing a functioning quantum computer. As quantum technologies develop, it is important to understand the computational resources needed to conduct unitary process tomography using a variety of types of circuits. In particular, when measuring error in diamond distance, it is known how to achieve optimal query complexity using a sequential circuit architecture, but it had not been known whether a parallel circuit architecture could achieve the same optimal query complexity. In this work, we prove that unitary process tomography with near-optimal query complexity is indeed possible using a parallel circuit by introducing an explicit, novel parallel procedure. This closes the gap between sequential and parallel circuits up to a logarithmic factor, showing that parallel and sequential strategies are nearly equally capable for this task.

arXiv:2609.36127 [quant-ph]

(or arXiv:2609.36127v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.36127 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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