PIRSA:25110098

Bipartite quantum states admitting a causal explanation

Song, M. (2025). Bipartite quantum states admitting a causal explanation. Perimeter Institute. https://pirsa.org/25110098

Song, Minjeong. Bipartite quantum states admitting a causal explanation. Perimeter Institute, Nov. 10, 2025, https://pirsa.org/25110098 

          @misc{ pirsa_PIRSA:25110098,
            doi = {10.48660/25110098},
            url = {https://pirsa.org/25110098},
            author = {Song, Minjeong},
            keywords = {Quantum Foundations},
            language = {en},
            title = {Bipartite quantum states admitting a causal explanation},
            publisher = {Perimeter Institute},
            year = {2025},
            month = {nov},
            note = {PIRSA:25110098 see, \url{https://pirsa.org}}
          }

Minjeong Song National University of Singapore

Talk numberPIRSA:25110098
DOI10.48660/25110098
Collection
Talk Type Scientific Series
Subject

Abstract

Abstract: In this talk, I will present our recent results in https://arxiv.org/abs/2507.14278: The statistics of local measurements of joint quantum systems can sometimes be used to distinguish the spatiotemporal structure in which they were measured.
We first prove that every bipartite separable density matrix is temporally compatible with direct causal influence for arbitrary finite-dimensional quantum systems and measurements of a tomographically-complete class of observables, which includes all Pauli observables in the case of multi-qubit systems. Equivalently, if a bipartite density matrix is not temporally compatible with direct causal influence, then it must be entangled. We also provide an operational meaning for the temporal evolution consistent with such correlations in terms of a generalized dephasing channel and a pretty good measurement. The two temporal evolutions are Bayesian inverses of each other, which is different from them being Petz recovery maps of each other. Finally, we prove necessary and sufficient conditions for an arbitrary bipartite quantum state to be temporally compatible, thereby providing a temporal analogue of the positive partial transpose criterion valid for quantum systems of any dimension. If time permits, I will also introduce other works that I currently am working on, which is the implementation of Petz recovery maps.