Paper published in npj Quantum Information!

Paper on Hamiltonian recognition is published in npj Quantum Information 🎉

Content (Leave links as citations and fill them below) Our paper Optimal Hamiltonian recognition of unknown quantum dynamics by Chengkai Zhu, Shuyu He, Yu-Ao Chen, Lei Zhang and Xin Wang is published in npj Quantum Information!

For npj Quantum Information: npj Quantum Information is a Nature Portfolio journal that publishes high-quality research on all aspects of quantum information science, including quantum computing, quantum communication, quantum metrology, and quantum foundations. As part of the Nature Partner Journals initiative, it aims to bridge the gap between fundamental quantum physics and practical quantum technologies.

For the paper Optimal Hamiltonian recognition of unknown quantum dynamics: Identifying unknown Hamiltonians from their quantum dynamics is a pivotal challenge in quantum technologies. We introduce Hamiltonian recognition, a framework that bridges quantum hypothesis testing and quantum metrology, aiming to identify the Hamiltonian governing quantum dynamics from a known set of Hamiltonians. For binary recognition of orthogonal single-qubit Hamiltonians, we develop a quantum algorithm based on quantum signal processing (QSP) that achieves an optimal average error of O(1/k) with k queries to the unknown unitary transformation, a scaling proven optimal via semidefinite programming and group representation theory. We also develop an optimal quantum algorithm for ternary recognition of three orthogonal Hamiltonians. Remarkably, our results reveal that two disjoint sets of unitary operations can be perfectly discriminated with finite adaptive queries without entanglement. We validate our protocol on a superconducting quantum processor and provide numerical evidence for effective multi-qubit Hamiltonian recognition on Heisenberg-type models. This work presents an efficient method to recognize Hamiltonians from limited queries of the dynamics, opening new avenues in composite channel discrimination and quantum metrology.