Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Concentration of measure for quantum states with a fixed expectation
  value   Given some observable H of a finite-dimensional quantum system, we
investigate the typical properties of random quantum state vectors that have a
fixed expectation value with respect to H. Under some some conditions on the
spectrum, we prove that this manifold of quantum states shows a concentration
of measure phenomenon: any continuous function on this set is almost everywhere
close to its mean. We also give a method to estimate the corresponding
expectation values analytically, and we prove a formula for the typical reduced
density matrix in the case that H is a sum of local observables. We discuss the
implications of our results as new proof tools in quantum information theory
and to study phenomena in quantum statistical mechanics. As a by-product, we
derive a method to sample the resulting distribution numerically, which
generalizes the well-known Gaussian method to draw random states from the
sphere.

24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
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
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph