Enhanced measurements on quantum computers via the simultaneous probing of non-commuting Pauli operators

Abstract: Measuring the state of quantum computers is a highly non-trivial task, with implications for virtually all quantum algorithms. We propose a novel scheme where identical copies of a quantum state are measured jointly so that all Pauli operators within the considered observable can be simultaneously assessed. We use Bayesian statistics to accurately estimate the average and error, and develop an adaptive shot-allocation algorithm that preferentially samples the most uncertain Pauli terms. In regimes with many non-commuting Pauli operators, our ``double'' scheme can outperform the state-of-the-art measurement protocol in minimizing total shots for a given precision.