Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recycling of quantum information: Multiple observations of quantum
  clocks   How much information about the original state preparation can be extracted
from a quantum system which already has been measured? That is, how many
independent (non-communicating) observers can measure the quantum system
sequentially and give a nontrivial estimation of the original unknown state? We
investigate these questions and we show from a simple example that quantum
information is not entirely lost as a result of the measurement-induced
collapse of the quantum state, and that an infinite number of independent
observers who have no prior knowledge about the initial state can gain a
partial information about the original preparation of the quantum system.

23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
1
The categories of this paper are: cs