Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The power of being positive: Robust state estimation made possible by
  quantum mechanics   We study the problem of quantum-state tomography under the assumption that
the state of the system is close to pure. In this context, an efficient
measurements that one typically formulates uniquely identify a pure state from
within the set of other pure states. In general such measurements are not
robust in the presence of measurement noise and other imperfections, and
therefore are less practical for tomography. We argue here that state
tomography experiments should instead be done using measurements that can
distinguish a pure state from {\em any} other quantum state, of any rank. We
show that such nontrivial measurements follows from the physical constraint
that the density matrix is positive semidefinite and prove that these
measurements yield a robust estimation of the state. We assert that one can
implement such tomography relatively simply by measuring only a few random
orthonormal bases; our conjecture is supported by numerical evidence. These
results are generalized for estimation of states close to bounded-rank.

17
The categories of this paper are: q-fin
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat