Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Forcing a unitary transformation by an external field: comparing two
  approaches based on optimal control theory   A quantum gate is realized by specific unitary transformations operating on
states representing qubits. Considering a quantum system employed as an element
in a quantum computing scheme, the task is therefore to enforce the
pre-specified unitary transformation. This task is carried out by an external
time dependent field. Optimal control theory has been suggested as a method to
compute the external field which alters the evolution of the system such that
it performs the desire unitary transformation. This study compares two recent
implementations of optimal control theory to find the field that induces a
quantum gate. The first approach is based on the equation of motion of the
unitary transformation. The second approach generalizes the state to state
formulation of optimal control theory. This work highlight the formal relation
between the two approaches.

30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex