Speaker
Description
Quantum process tomography provides complete information about the dynamics of a quantum system, but its practical use is severely limited by the exponential resources required to characterize generic quantum channels. This challenge is particularly relevant for the characterization of noise in quantum devices, where understanding coherent and correlated errors is essential for benchmarking, error mitigation, and fault-tolerant quantum computing.
In this work, we introduce an efficient and experimentally feasible protocol for the complete reconstruction of low-degree noise channels. Our approach assumes access only to single-qubit state preparation and measurement, making it directly compatible with current quantum hardware. The protocol builds on the framework of shadow tomography, but departs from standard constructions by exploiting the non-uniqueness of the reconstruction function. By tailoring this reconstruction map to the low-degree structure of the noise, we obtain a rigorous reduction of the sample complexity from exponential to polynomial in the system size.
We further show how to isolate the noise associated with a layer of quantum gates without averaging away coherent information, enabling the characterization of both coherent and correlated errors. The resulting method provides complete tomography of a broad class of physically relevant noise processes while retaining the scalability and experimental simplicity of randomized-measurement protocols.
Our results establish low-degree channels as a tractable regime for quantum process tomography and provide a practical framework for noise diagnostics in near-term quantum devices.
| Topic | Quantum state reconstruction from data |
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