Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Performing joint measurements and transformations on several qubits by
  operating on a single control qubit   An n-qubit quantum register can in principle be completely controlled by
operating on a single qubit that interacts with the register via an appropriate
fixed interaction. We consider a hypothetical system consisting of n spin-1/2
nuclei that interact with an electron spin via a magnetic interaction. We
describe algorithms that measure non-trivial joint observables on the register
by acting on the control spin only. For large n this is not an efficient model
for universal quantum computation but it can be modified to an efficient one if
one allows n possible positions of the control particle.
  This toy model of measurements illustrates in which way specific interactions
between the register and a probe particle support specific types of joint
measurements in the sense that some joint observables can be measured by simple
sequences of operations on the probe particle.

30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom