Unification of spatiotemporal quantum formalisms: mapping between process and pseudo-density matrices via multiple-time states

• DOI: 10.1088/1367-2630/ad264c
• Publication Date: 2024-02-05T22:27:36Z
• Authors: Xiangjing Liu; Zhian Jia; Yixian Qiu; Fei Li; Oscar Dahlsten
• Keywords: Unification; Density matrix; Matrix (chemical analysis)

Abstract We consider the relation between three different approaches to defining quantum states across several times and locations: pseudo-density matrix (PDM), process matrix, multiple-time state approaches. Previous studies have shown that bipartite two-time can reproduce statistics of matrices. Here, we show operational scenarios underlying be represented as PDMs, thereby construct a mapping from matrices with measurements PDMs. The existence this implies PDMs can, like model processes indefinite causal orders. results contribute unification models spatiotemporal states.