Southwest Quantum Information and Technology

Hyper-Accurate Gate Set Tomography

Kenneth Rudinger, Sandia National Laboratories

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Standard quantum tomography is limited by its reliance on precalibrated states/measurements/operations, which are unavailable in many physical qubit systems. Gate set tomography (GST) is a tomographic framework introduced to solve this problem of self-referential calibration. Previous work demonstrated that GST can successfully reconstruct quantum states and processes with reasonable accuracy, using closed-form linear inversion of data obtained from short sequences of quantum operations. In this talk, we demonstrate algorithms for "long-sequence GST", which enable efficient analysis of data from experiments involving long sequences of gates. We also show how to choose long sequences that amplify every possible error in the gate set. Together, these techniques produce GST estimates whose accuracy is limited not by 1/sqrt(N) (where N is the number of measurements), but by 1/L, where L is the length of the longest gate sequence. We show simulations and experimental results (including trapped-ion, neutral atom, and semiconductor qubits) that confirm accuracy better than 1e-4 in the gate elements. This work was supported in part by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.