Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Instantaneous Quantum Channel Estimation during Quantum Information
  Processing   We present a nonintrusive method for reliably estimating the noise level
during quantum computation and quantum communication protected by quantum
error-correcting codes. As preprocessing of quantum error correction, our
scheme estimates the current noise level through a negligible amount of
classical computation using error syndromes and updates the decoder's knowledge
on the spot before inferring the locations of errors. This preprocessing
requires no additional quantum interaction or modification in the system. The
estimate can be of higher quality than the maximum likelihood estimate based on
perfect knowledge of channel parameters, thereby eliminating the need of the
unrealistic assumption that the decoder accurately knows channel parameters a
priori. Simulations demonstrate that not only can the decoder pick up on a
change of channel parameters, but even if the channel stays the same, a quantum
low-density parity-check code can perform better when the decoder exploits the
on-the-spot estimates instead of the true error probabilities of the quantum
channel.

4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int