Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optimal control theory for quantum electrodynamics: an initial state
  problem   In conventional quantum optimal control theory, the parameters that determine
an external field are optimised to maximise some predefined function of the
trajectory, or of the final state, of a matter system. The situation changes in
the case of quantum electrodynamics, where the degrees of freedom of the
radiation field are now part of the system. In consequence, instead of
optimising an external field, the optimal control question turns into a
optimisation problem for the many-body initial state of the combined
matter-photon system. In the present work, we develop such a optimal control
theory for quantum electrodynamics. We derive the equation that provides the
gradient of the target function, which is often the occupation of some given
state or subspace, with respect to the control variables that define the
initial state. We choose the well-known Dicke model to study the possibilities
of this technique. In the weak coupling regime, we find that Dicke states are
the optimal matter states to reach Fock number states of the cavity mode with
large fidelity, and vice versa, that Fock number states of the photon modes are
the optimal states to reach the Dicke states. This picture does not prevail in
the strong coupling regime. We have also considered the extended case with more
than one mode. In this case, we find that increasing the number of two-level
systems allows to reach a larger occupation of entangled photon targets.

2
The categories of this paper are: math
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex