CAPÍTULO III.MATERIALES Y MÉTODOS
2.3 P ROCEDIMIENTO
2.3.3.2.11 Consideraciones legislativas en cuanto al cifrado de datos
When a moleule is exposed to a shaped, intense laser pulse the optimiza-
tion has to aomplish two things. First, the optimization has to reate a
wavepaketonsistingofalargenumberofrotationalstatesthatanserveto
align the moleule. Seond,theoptimization hasto preparethewavepaket
withtheorretphaserelationshipbetweentheomponentwavefuntions,so
thatduringitseld-freeevolutiontheseomponentswouldoherentlyadd-up
to generate an optimally aligned wavefuntion. While thereis no riterium
available that allows us to asertain whether the algorithm has optimized
the populationdistribution, itis possible to investigate the phaserelation-
ship ofthe omponent wavefuntionsinthe optimized solutions. Maximum
alignmentoursifatsomepointintimethe phasesofall omponentwave-
funtionsdierfrom eahother by 0(modulo
2π
). Expliitly,given awavefuntion,ψ=X
j
a(jt)· |ji ·exp
−iEjt
~
,
the oeientsa
(t)
j
are omplex numbers, and assuh an be expressed in their polar representation:a(jt)=r(jt)·expiϕ(jt).
(9.9) Wethusquestionwhethergivenaertainpopulation-doestheoptimizationroutine produe the optimal set of phases
ϕ
(t)
j
? In order to answer this question,asimpleoptimization proedurewasimplementedinthefollowingmanner: It aeptsthe
a
(t)
j
asinput, andaimsat optimizingthephasesϕ
(t)
Figure 9.15: TOP: The distribution of the maximal and the best opti-
mized wavepakets over the rotational states. Stars represent the maximal
wavepaket inthe nite rotational basis(i.e., orrespondingto thehighest-
ranked eigenvetor of the observable matrix). Diamonds represent the
1
st
optimized setof solutions (CMA-Hermite/ DR2-Plain),and Squaresrepre-
sentthe
2
nd
optimizedsetofsolutions(CMA-Plain/DR2-Hermite);Cirles
represent alulations with doubled bandwidth and the same uene (
50fs
pulse withΩge
= 226
×10
12s−1
), optimized by the DR2 subjet to plain
parameterization. Thegure learlyshows thatthelimitedeldbandwidth
uts othe rotational statesfor theoptimized solutions after
J
= 10
,when the original bandwidthis used,or afterJ
= 12
whenthebandwidthis dou- bled. Furthermore,thisplotillustratesthedistintionbetweenthetwofamilies of solutions for the original bandwidth (i.e., Diamonds ver-
sus Squares) arising from the dierent algorithmi approahes. BOTTOM:
Thealignment asafuntionoftheoverlapoftheoptimizedwavepakets
|Ψi
with the maximal eigenvetor|Vi
. Note that the overlap for the original bandwidth never exeeds0.8
in magnitude. Also note the three lustersFigure9.16: Leftaxis: Normalizedangular probabilitydistributionfuntion
for the maximal ase
|ψmax(θ)|
2sin (θ)
, and theoptimized ontrol funtion
|ψopt(θ)|2sin (θ)
. Right axis: The value ofcos
2(θ)
. The onstraints pro-
hibit theevolutionaryalgorithmfromattaining theabsolutemaximalangu-
lar probability distribution funtion; However, theexpetation value of the
observable
cos2(θ)
opt
= 0.9621
when using theoriginal bandwidth orre- sponding to a100fs
Fourier-limited pulse is within0.025
of the maximum attainablevaluecos2(θ)
max
= 0.9863
. Whendoublingthebandwidth(i.e., basing the shaped laser pulse on a50fs
Fourier-limited pulse)cos2(θ)
opt
inreases to
0.975
,whihis only0.0113
away fromthemaximumattainable value.suh that the osine-squaredalignment is maximized. Pratially, it uses a
subroutine from the general alignment ode for the evaluation, and applies
the CMA algorithm for the tuning of the
10
relevant phases. Note that a single funtionevaluationhasthe duration of≈0.5s
.Weonsidered
50
dierentasesofhigh-qualitysolutionstothealignment problem(allsolutions haveosine-squared-alignment valuesintheregimeof0.95
) -for eahtestase100
independent optimizationswererun,aimingto tune the phases.Theexperimentalresultsarelearandsharp. Theyarepresentedattwo
levels:
1. In all
100
runs for all50
test-ases - the best solution has always synhronized phases. There are dierent phasevalues per run, butitdoesnot make adierenefor theosine-squaredalignment,aslong
as the populated levels hold that same phase value. Expliitly, the
Sigma-RMSof the phases wasalulated:
2. The
50
test-ases, as originally obtained by the original optimization prior to this optimization proedure, held phases whih were not farfrom beingsynhronized,
∆ϕDR2= 0.0566,
andindeed,theoptimizationsdidnotimprovetheosine-squaredalign-
ment dramatially: Alwayslessthan 1%improvement wasreorded.
We onsiderthisaverystrongresult-theevolutionaryoptimization routine
managed to takle the ne-tuning of the quantum ontrol problem, behind
theomplex transformationsand theso-alled Shrödingerblak-box.
To summarize, while we annot establish whether the optimization has
distributed the populationinthe best possible way, we do observe that the
algorithm hasproperlyphased-upallomponent wavefuntionswithrespet
to eah other. Thistype of oherent alignment of phases was also observed
to be optimal in the mehanisti analysis of another state-to-state ontrol
appliation [163 ℄.