Reconstructing Quantum States from Local Observation: A Dynamical Viewpoint

We analyze the problem of reconstructing an unknown quantum state of a multipartite system from repeated measurements of local observables. In particular, via a system-theoretic observability analysis, we show that, even when the initial state is not uniquely determined for a static system, this can be reconstructed if we leverage the system’s dynamics. The choice of dynamical generators and the effect of finite samples is discussed, along with an illustrative example.