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arXiv · 2212.07710

Quantum memory assisted observable estimation

Liubov A. Markovich·Attaallah Almasi·Sina Zeytinoğlu·Johannes Borregaard
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Abstract

The estimation of many-qubit observables is an essential task of quantum information processing. The generally applicable approach is to decompose the observables into weighted sums of multi-qubit Pauli strings, i.e., tensor products of single-qubit Pauli matrices, which can readily be measured with single qubit rotations. The accumulation of shot noise in this approach, however, severely limits the achievable variance for a finite number of measurements. We introduce a novel method, dubbed Coherent Pauli Summation (CPS) that circumvents this limitation by exploiting access to a single-qubit quantum memory in which measurement information can be stored and accumulated. Our algorithm offers a reduction in the required number of measurements for a given variance that scales linearly with the number of Pauli strings of the decomposed observable. Our work demonstrates how a single long-coherence qubit memory can assist the operation of noisy many-qubit quantum devices in a cardinal task.

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Liubov A. Markovich, Attaallah Almasi, Sina Zeytinoğlu, Johannes Borregaard. 2022-12-15. Quantum memory assisted observable estimation. https://doi.org/10.22331/q-2025-03-06-1655

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