Ansatz-Free Learning of Lindbladian Dynamics In Situ

Characterizing the dynamics of open quantum systems at the level of microscopic interactions and error mechanisms is essential for calibrating quantum hardware, designing robust simulation protocols, and developing tailored error-correction methods. Under Markovian noise/dissipation, a natural characterization approach is to identify the full Lindbladian generator that gives rise to both coherent (Hamiltonian) and dissipative dynamics. Prior protocols for learning Lindbladians from dynamical data assumed pre-specified interaction structure, which can be restrictive when the relevant noise channels or control imperfections are not known in advance. In this paper, we present the first sample-efficient protocol for learning sparse Lindbladians without assuming any a priori structure or locality. Our protocol is ancilla-free, uses only product-state preparations and Pauli-basis measurements, and achieves near-optimal time resolution, making it compatible with near-term experimental capabilities. The final sample complexity depends on linear-system conditioning, which we find empirically to be moderate for a broad class of physically motivated models. Together, this provides a systematic route to scalable characterization of open-system quantum dynamics, especially in settings where the error mechanisms of interest are unknown.

💡 Research Summary

The paper tackles the problem of learning the full Lindblad generator of a Markovian open‑quantum system without assuming any prior structure such as locality or a specific set of noise channels. Existing methods either focus on Hamiltonian learning under idealized conditions or require knowledge of the Lindbladian’s sparsity pattern, which limits their applicability to realistic devices where error mechanisms can be complex and non‑local.

The authors model an n‑qubit Lindbladian as a sparse sum of Pauli operators: a Hamiltonian part (−i∑_{P_i∈S_H} h_i