Everett's relative-state construction in quantum theory has never been satisfactorily expressed in the Heisenberg picture. What one might have expected to be a straightforward process was impeded by conceptual and technical problems that we solve here. The result is a construction which, unlike Everett's one in the Schrödinger picture, makes manifest the locality of Everettian multiplicity, its inherently approximative nature and its origin in certain kinds of entanglement and locally inaccessible information. (By Everettian, we are referring not only to Everett's own work, but also to versions of quantum theory that elaborate and refine his. The notion of relative states first appeared in Everett (Everett 1973 In The many worlds interpretation of quantum mechanics (eds BS DeWitt, N Graham)). We are proposing a formalism for relative states that is more detailed and more illuminating than Everett's.) Our construction also allows us to give a more precise definition of an Everett ‘universe’, under which it is fully quantum, not quasi-classical, and we compare the Everettian decomposition of a quantum state with the foliation of a space–time.

埃弗雷特在量子理论中的相对态构造从未在海森堡的图景中得到令人满意的表达。我们在这里解决的概念和技术问题阻碍了人们可能期望的简单过程。结果是一种构造，与埃弗雷特在薛定谔的画中的构造不同，它表明了埃弗雷特多重性的局部性、其固有的近似性以及它起源于某些类型的纠缠和局部无法访问的信息。（通过Everettian，我们不仅指的是 Everett 自己的工作，而且还指的是阐述和完善他的量子理论的版本。相对状态的概念首先出现在 Everett 中（Everett 1973 在量子力学的多世界解释中（编辑 BS DeWitt，N Graham））。我们提出了一种相对状态的形式，它比埃弗雷特的更详细和更有启发性。）我们的构造还允许我们对埃弗雷特“宇宙”给出更精确的定义，在这个定义下，它是完全量子的，而不是准经典的，并且我们将量子态的 Everettian 分解与时空的叶状化进行了比较。