Difference between revisions of "Quantum Control"

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[[Image:quantum control.jpg|center|500px]]
 
[[Image:quantum control.jpg|center|500px]]
  
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A shaped ultrafast pulse makes it possible to stir a quantum system and thus control a quantum process via light-matter interaction. Two photon absorption(TPA) process in two-level atoms is one of the good testbed for coherent control. We study coherent control schemes for a TPA process in a strong field. For a optimal coherent scheme to enhance TPA, strong field effects(dynamic Stark shift) have been considered.
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A shaped ultrafast pulse makes it possible to steer a quantum system and thus control a quantum process via light-matter interaction. Two photon absorption (TPA) process in two-level atoms is one of the good testbed for coherent control. We study coherent control schemes for a TPA process in a strong field. For a optimal coherent scheme to enhance TPA, strong field effects (dynamic Stark shift) have been considered.
  
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[[Image:Setup_dazzler.jpg|center|200px]]
 
  
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<center>''Fig.1: schematic diagram of the experimental setup''</center>
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<big>'''Strong-field two-photon absorption in atomic cesium: an analytical control approach</big><br>
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#[[Image:Setup_dazzler.jpg|thumb|''Fig.1: schematic diagram of the experimental setup''|center|200px]]
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[[Image:Strongfield.jpg|left|200px]]
  
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We have considered an analytical control of two-photon absorption
 +
process of atoms in the strong-field interaction regime. The experiment
 +
was performed on gaseous cesium atoms strongly interacting with a
 +
shaped laser-pulse from a femtosecond laser amplifier and a programmable
 +
pulse-shaper. When this shaped laser-pulse transfers the atomic population
 +
from the 6s ground state to the 8s excited state, we have found that both
 +
positively- and negatively-chirped laser pulses, compared with a Gaussian
 +
pulse, enhance this excitation in the strong-field regime of laser-atom
 +
interaction. This unusual phenomena is explained because the temporal
 +
shape of the laser intensity compensates the effect of dynamic Stark shift for
 +
the two-photon resonant condition to be optimally maintained. We provide
 +
analytic calculations using the strong-field phase matching, which show
 +
good agreement with the experiment.
 +
[http://www.opticsinfobase.org/abstract.cfm?uri=oe-17-9-7648 27 April 2009 / Vol. 17, No. 9 / OPTICS EXPRESS 7648]
  
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In weak field reigme, a transform-limited pulse is a optimal pulse to enhance a TPA. But it is not a optimal solution in strong field. The dynamic Stark shift disturbs a TPA process.
 
  
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[[Image:Intensity_total_v4.jpg|center|200px]]
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<big>'''Strong-Field two-photon transition by phase shaping</big><br>
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[[Image:Rb_TPA.jpg|left|150px]]
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We demonstrate the ultrafast coherent control of a non-linear two-photon absorption in a dy-
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namically shifted energy level structure. We use a spectro-temporal laser pulse shaping that is programmed to preserve the resonant absorption condition during the intense laser ¯eld interaction. Experiments carried out in the strong-¯eld regime of two-photon absorption in the ground state of atomic Cesium reveal that the analytically obtained o®set and curvature of a laser spectrum compensate the effect of both static and dynamic energy shifts of the given light-atom interaction.
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Sangkyung Lee, Jongseok Lim, Jaewook Ahn, Vahe Hakobyan, and Stephane Guerin, "Strong-field two-level two-photon transition by phase shaping," Physical Review A 82, 023408 (August 2010). [[Media:SangkyungPRA2010.pdf]]  
  
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<center>''Fig.2: fluoresence as a function of chirp rates and transform-limited intensity of pulses''</center>
 
  
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A linear chirped pulse is more optimal than a transform-limited pulse.  
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<big>'''Coherent Control in 2D-FTES'''</big><br>
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[[Image:2D_FTES-highlight.JPG‎|left|150px]]
  
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We demonstrate the advantage of applying coherent control technique to 2D-FTES spectroscopy. By shaping individual pulses used in 2D-FTES on atomic model system, we selectively turn on and off specific couplings. This advanced 2D-FTES technique may be useful for probing time-dependent coupling paths among multilevel electronic energy states in complex systems
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Jongseok Lim, Han-gyeol Lee, Jae-uk Kim, Sangkyung Lee, and Jaewook Ahn, "Coherent transients mimicked by two-photon coherent control of three-level system," Phys. Rev. A, 83, 053429 (May 2011). [[Media:LimPRA2011.pdf]]
  
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[[Image:Detuning_total_v6.jpg|center|200px]]
 
  
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<center>''Fig.3: fluorescence as a function of detuning and chirp rates''</center>
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<br><br><br><br>

Latest revision as of 04:59, 17 June 2011

Two photon absorption in strong field

Quantum control.jpg

A shaped ultrafast pulse makes it possible to steer a quantum system and thus control a quantum process via light-matter interaction. Two photon absorption (TPA) process in two-level atoms is one of the good testbed for coherent control. We study coherent control schemes for a TPA process in a strong field. For a optimal coherent scheme to enhance TPA, strong field effects (dynamic Stark shift) have been considered.


Strong-field two-photon absorption in atomic cesium: an analytical control approach

Strongfield.jpg

We have considered an analytical control of two-photon absorption process of atoms in the strong-field interaction regime. The experiment was performed on gaseous cesium atoms strongly interacting with a shaped laser-pulse from a femtosecond laser amplifier and a programmable pulse-shaper. When this shaped laser-pulse transfers the atomic population from the 6s ground state to the 8s excited state, we have found that both positively- and negatively-chirped laser pulses, compared with a Gaussian pulse, enhance this excitation in the strong-field regime of laser-atom interaction. This unusual phenomena is explained because the temporal shape of the laser intensity compensates the effect of dynamic Stark shift for the two-photon resonant condition to be optimally maintained. We provide analytic calculations using the strong-field phase matching, which show good agreement with the experiment. 27 April 2009 / Vol. 17, No. 9 / OPTICS EXPRESS 7648


Strong-Field two-photon transition by phase shaping

Rb TPA.jpg

We demonstrate the ultrafast coherent control of a non-linear two-photon absorption in a dy- namically shifted energy level structure. We use a spectro-temporal laser pulse shaping that is programmed to preserve the resonant absorption condition during the intense laser ¯eld interaction. Experiments carried out in the strong-¯eld regime of two-photon absorption in the ground state of atomic Cesium reveal that the analytically obtained o®set and curvature of a laser spectrum compensate the effect of both static and dynamic energy shifts of the given light-atom interaction. Sangkyung Lee, Jongseok Lim, Jaewook Ahn, Vahe Hakobyan, and Stephane Guerin, "Strong-field two-level two-photon transition by phase shaping," Physical Review A 82, 023408 (August 2010). Media:SangkyungPRA2010.pdf


Coherent Control in 2D-FTES

2D FTES-highlight.JPG

We demonstrate the advantage of applying coherent control technique to 2D-FTES spectroscopy. By shaping individual pulses used in 2D-FTES on atomic model system, we selectively turn on and off specific couplings. This advanced 2D-FTES technique may be useful for probing time-dependent coupling paths among multilevel electronic energy states in complex systems Jongseok Lim, Han-gyeol Lee, Jae-uk Kim, Sangkyung Lee, and Jaewook Ahn, "Coherent transients mimicked by two-photon coherent control of three-level system," Phys. Rev. A, 83, 053429 (May 2011). Media:LimPRA2011.pdf






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