Thrifty shadow estimation: Reusing quantum circuits and bounding tails
Physical Review Letters , Volume 131 - Issue 24 p. 240602
Shadow estimation is a recent protocol that allows estimating exponentially many expectation values of a quantum state from "classical shadows,"obtained by applying random quantum circuits and computational basis measurements. In this Letter we study the statistical efficiency of this approach in light of near-term quantum computing. We propose a more practical variant of the protocol, thrifty shadow estimation, in which quantum circuits are reused many times instead of having to be freshly generated for each measurement. We show that reuse is maximally effective when sampling Haar random unitaries, and maximally ineffective when sampling from the Clifford group, i.e., one should not reuse circuits when performing shadow estimation with the Clifford group. We provide an efficiently simulable family of quantum circuits that interpolates between these extremes, which we believe should be used instead of the Clifford group. Finally, we consider tail bounds for shadow estimation and discuss when median-of-means estimation can be replaced with standard mean estimation.
|Physical Review Letters
|Quantum Software Consortium
|Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands
Helsen, J., & Walter, M. (2023). Thrifty shadow estimation: Reusing quantum circuits and bounding tails. Physical Review Letters, 131(24). doi:10.1103/PhysRevLett.131.240602