Paper accepted by PRX Quantum!

Paper on estimating high-order quantum information has been accepted for publication in PRX Quantum 🎉

Our paper Retrieving non-linear features from noisy quantum states by Benchi Zhao, Mingrui Jing, Lei Zhang, Yu-Ao Chen, Kun Wang and Xin Wang has been accepted for publication in PRX Quantum 🎉

For PRX Quantum: PRX Quantum is a highly selective, online-only, fully open access journal that publishes research with an emphasis on outstanding and lasting impact. PRX Quantum seeks to publish a select set of papers providing a home for and connection between the numerous research communities that make up quantum information science and technology, spanning from pure science to engineering to computer science and beyond.

For the paper Retrieving non-linear features from noisy quantum states: Accurately estimating high-order moments of quantum states is an elementary precondition for many crucial tasks in quantum computing, such as entanglement spectroscopy, entropy estimation, spectrum estimation, and predicting non-linear features from quantum states. But in reality, inevitable quantum noise prevents us from accessing the desired value. In this paper, we address this issue by systematically analyzing the feasibility and efficiency of extracting high-order moments from noisy states. We first show that there exists a quantum protocol capable of accomplishing this task if and only if the underlying noise channel is invertible. We then establish a method for deriving protocols that attain optimal sample complexity using quantum operations and classical post-processing only. Our protocols, in contrast to conventional ones, incur lower overheads and avoid sampling different quantum operations due to a novel technique called observable shift, making the protocols strong candidates for practical usage on current quantum devices. The proposed method also indicates the power of entangled protocols in retrieving high-order information, whereas in the existing methods, entanglement does not help. We further construct the protocol for large quantum systems to retrieve the depolarizing channels, making the proposed method scalable. Our work contributes to a deeper understanding of how quantum noise could affect high-order information extraction and provides guidance on how to tackle it.