45 citations · 120 across the 6 of their papers we have counts for
6 papers
On extrema of the objective functional for short-time generation of single qubit quantum gates
Alexander Pechen, Nikolay Il'in
In the present work the extrema of the objective functional for the problem of generation of quantum gates (logical elements for quantum computations) for two--level systems are in…
Control landscape for ultrafast manipulation by a qubit
Alexander Pechen, Nikolay Il'in
In this work we study extrema of objective functionals for ultrafast manipulation by a qubit. Traps are extrema of the objective functionals which are optimal for manipulation by q…
Squaring parametrization of constrained and unconstrained sets of quantum states
N. Il'in, E. Shpagina, F. Uskov +1
A mixed quantum state is represented by a Hermitian positive semi-definite operator with unit trace. The positivity requirement is responsible for a highly nontrivial geometry…
On critical points of the objective functional for maximization of qubit observables
Alexander Pechen, Nikolay Il'in
We study unconstrained control of a two-level quantum system and analyse critical points of the objective functional which represents quantum average of system observable at some f…
Coherent control of a qubit is trap-free
Alexander Pechen, Nikolay Il'in
There is a strong interest in optimal manipulating of quantum systems by external controls. Traps are controls which are optimal only locally but not globally. If they exist, they…
Trap-free manipulation in the Landau-Zener system
Alexander Pechen, Nikolay Il'in
The analysis of traps, i.e., locally but not globally optimal controls, for quantum control systems has attracted a great interest in recent years. The central problem that has bee…