Speaker: Marcus Motzkus (University of Marburg)

Title: Spectroscopy of biological molecules using coherent control

Coherent control as a field of current research has expanded significantly in recent years. In chemistry the core competence remains the steering of photo-induced processes into a desired channel while suppressing unwanted pathways. Also in biology it has been experimentally demonstrated in natural occurring complexes [1,2] as well as in artificial dyads [3] that the ratio between reaction pathways can be influenced by phase and amplitude shaped laser pulses.

In addition to this pure optimization process, the concept of coherent control offers also a novel approach for the study of general light-mater interaction and in particular for the application of optical spectroscopy. Not only new insight into the complex dynamics in large molecules is obtained by comparison of shaped and unshaped laser pulses but also robust and simplified implementations of powerful nonlinear optical techniques are easily realized. This idea forms the conceptual basis of Quantum Control Spectroscopy (QCS) and has already yielded important results on molecular vibrational dynamics and biological function unattainable by conventional spectroscopic techniques.[1,3-5]

In this contribution we employ QCS to unravel the ultrafast dynamics near a conical intersection between the two electronicly excited states S2 and S1 in ß-carotene[5-7] and new developments will be presented which cover different directions of coherent control from medical applications to the development of multiphoton microscopy.[8]

[1] J. L. Herek et al., Nature 417, 533 (2002).

[2] V.I. Prokhorenko et al., Science 313, 1257 (2006)

[3] J. Savolainen et al., PNAS 105, 7641 (2008).

[4] T. Buckup et al., Journal of Photochemistry and Photobiology A 180, 314 (2006).

[5] J. Hauer et al., Chem Phys 350, 220 (2008)

[6] J. Hauer et al., Journal of Physical Chemistry A 111, 10517 (2007).

[7] J. Hauer et al., Chem. Phys. Lett. 421, 523 (2006)

[8] B. von Vacano and M. Motzkus, PCCP 10, 186 (2008).

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Speaker: Evgeny Shapiro (The University of British Columbia)

Title: "Piecewise'' vs. ``Coherently controlled'' adiabatic passage

Coauthors: Moshe Shapiro, Valery Milner

We develop a technique for executing robust and selective transfer of populations between pre-selected superpositions of energy eigenstates. Viewed in the frequency domain, our methods stem from the idea of Coherently Controlled Adiabatic Passage [1], in which several adiabatic passage pathways coherently add up to provide the desired population transfer. Viewed in the time domain, the methods work by piecewise accumulation of the wavefunction in the target wave packet, applying the Piecewise Adiabatic Passage technique [2] in the multi-state regime. The presentation will introduce the basic concepts behind the technique and will discuss its recent theoretical and experimental developments.

[1] P. Kral, I. Thanopulos, M. Shapiro, Rev. Mod. Phys. 79, 53 (2007). [2] E.A. Shapiro et.al., Phys. Rev. Lett. 99, 033002 (2007).

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Speaker: Nathan Wiebe (University of Calgary)

Title: Quantum Computer Simulations of Time Dependent Hamiltonians

Coauthors: Dominic Berry, Peter Hoyer, Barry Sanders

Feynman's original motivation for the quantum computer resulted from a conjecture that quantum computers could efficiently simulate any quantum system, whereas classical computers cannot. Since then many quantum simulation schemes have verified his conjecture for sparse time independent Hamiltonians. However all proposals that have been put forward so far for simulating time dependent Hamiltonians only address sparse Hamiltonians and have complexity that scales as O(t^{3/2}). We address these issues by presenting a quantum computer simulation scheme that can simulate many non-sparse time-dependent Hamiltonians that uses arbitrary-order decomposition formulae to achieve complexity of O(t^{1+epsilon)) for arbitrary epsilon>0, provided the time dependence is suitably smooth. Since O(t) complexity has been proven to be optimal, our simulation scheme demonstrates near optimal performance for the broadest class of Hamiltonians considered so far.