
Using OCT to realize a CNOT gate within 2D acetylene
----------------------------------------------------

The input files in this directory can be used to calculate an optimal
pulse for a controlled NOT gate using two modes of acetylene:
the asymmetric stretching (coordinate d) and the cis-bending
(coordinate R} modes.
(See for instance: Phys. Rev. Lett. 89, 157901 (2002))

In this example the qbits |ij> are defined as the ground state 0 and
the first exited state 1 in in the two modes where the first index i
labels the stretching mode and serves as the control bit while
j labels the bending mode. If the stretching mode is in the
first exited state, the bending mode is to be transfered from 0 to 1
or vice versa while leaving the state of the stretching mode unchanged.
In total:

  |00>  ->  |00>
  |01>  ->  |01>
  |10>  ->  |11>
  |11>  ->  |10>


To start the control job create a new empty directory and copy all input files
and directories

   mkdir <newdir>
   cd <newdir>
   cp -r $MCTDH_DIR/inputs/optcntrl/multi_target/acetylene_cnot/* .

First natpot files for the PES and dipole operators have to be created.
cd to the 'natpot' directory and type

   potfit84 -mnd <file>.inp

for all input files. Next type

   cd ../states

and create the qbit states mentioned above by typing

  mctdh84 -mnd <file>.inp

for all input files. This will create the corresponding eigenstates
of the system Hamiltonian using "improved relaxation".
Convergence of the states can be checked with 'showsys84'
in the respetive directories.

Start the control job with

   cd ../
   optcntrl -mnd ac_cnot.inp

This will create a directory 'cnot' where the calculation is
performed (this can take a while).






