5 papers
Optimal lower bound for quantum channel tomography in away-from-boundary regime
Kean Chen, Zhicheng Zhang, Nengkun Yu
Consider quantum channels with input dimension , output dimension and Kraus rank at most . Any such channel must satisfy the constraint , and the parame…
Quantum channel tomography and estimation by local test
Kean Chen, Nengkun Yu, Zhicheng Zhang
We study the estimation of an unknown quantum channel with input dimension , output dimension and Kraus rank at most . We establish a connection between…
A List of Complexity Bounds for Property Testing by Quantum Sample-to-Query Lifting
Kean Chen, Qisheng Wang, Zhicheng Zhang
Quantum sample-to-query lifting, a relation between quantum sample complexity and quantum query complexity presented in Wang and Zhang (SIAM J. Comput. 2025), was significantly str…
Inverse-free quantum state estimation with Heisenberg scaling
Kean Chen
In this paper, we present an inverse-free pure quantum state estimation protocol that achieves Heisenberg scaling. Specifically, let be a -dimens…
Simultaneous Estimation of Nonlinear Functionals of a Quantum State
Kean Chen, Qisheng Wang, Zhan Yu +1
We consider a fundamental task in quantum information theory, estimating the values of , , ..., for an obs…