Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Entanglement, joint measurement, and state reduction   Entanglement is perhaps the most important new feature of the quantum world.
It is expressed in quantum theory by the joint measurement formula. We prove
the formula for self-adjoint observables from a plausible assumption, which for
spacelike separated measurements is an expression of relativistic causality.
State reduction is simply a way to express the JMF after one measurement has
been made, and its result known.

16
The categories of this paper are: stat
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The categories of this paper are: eess
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
3
The categories of this paper are: physics