Quantum control mechanism

Fig. 4, An illustration of a Hamiltonian encoding-decoding analysis for revealing quantum control mechanisms. The contributions of the main pathways for the desired transition l) - 3 are shown in (a).

Vogt G, Nuernberger P, SeUe R, EHmler F, Brixner T, Gerber G (2006) Analysis of femtosecond quantum control mechanisms with colored double pulses. Phys Rev A 74 033413... 

The theory discussed in this paper treats the biased superlattices as onedimensional systems in a single particle envelope approximation in which the electrons and holes act independently. Scattering mechanisms, which cause a loss of coherence, have not yet been included in the formalism. Loss of coherence represents a significant obstacle to quantum control in... 

A fundamental issue concerns how to define control mechanism in the context of coherent quantum dynamics. Mechanism will likely be understood in a variety of ways, depending on the particular circumstances and control goals. However, an attractive perspective is to consider mechanism defined in terms of the amplitudes connecting the initial and final states, as depicted... 

In this contribution recent results [13] on the control of the quantum mechanical phase of an atomic state in strong laser fields studied using the Autler-Townes (AT) effect [14] in the photoionization of the K (4p) state are discussed. We demonstrate quantum control beyond (i) population control and (ii) spectral interference, (i) We show, that for suitable combinations of the laser intensity of the first pulse and the time delay the second resonant intense laser pulse leaves the excited state population unchanged. However, the knowledge of the... 

We demonstrate coherent control in strong fields beyond (i) population control and (ii) spectral interference, since (i) control is achieved without altering the population during the second intense laser pulse, i.e., the population during the second laser pulse is frozen, and (ii) the quantum mechanical phase is controlled without changing the spectrum of the pulse sequence. The control mechanism relies on the interplay of the quantum mechanical phase set by the intensity of the first pulse and the phase of the second pulse determined by the time delay. 

An important challenge is to explain the evidently contradictory outcome that quantum control does work and it is easy to find good solutions An analysis of this problem was recently undertaken [30] for various quantum mechanical objectives, with the generally most common case being... 

There are two fundamental questions that a model of chemical reactivity must answer as a prerequisite to becoming a paradigm What is the origin of the barriers And what are the factors that control reaction mechanisms Once a quantum chemical mechanism of barrier formation is formulated, understanding of reactivity patterns is likely to follow, and conceptual means will become available for the generation and solution of new... 

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