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Description
The two-state vector formalism is a time-symmetrised approach to quantum theory. Although its predictions can be derived from the principles of standard quantum mechanics, recent developments in constructing a covariant quantum field theory of particles with negative squared mass suggest that it may constitute a preferred interpretation. In our work, we identify an overlooked aspect of the formalism, which motivates the introduction of the concept of a story — a compatible pair consisting of a two-state vector and an ideal measurement. This notion carries fundamental physical significance within the formalism and provides a tool for examining the structure of the space of all two-state vectors. We analyze the problem of distinguishability and confirm that some pairs of two-state vectors or their statistical mixtures cannot be physically distinguished. This leads us to formulate the definition of a strictly non-separable two-state vector as a genuine manifestation of entanglement between the past and the future.