TY - JOUR
T1 - Molecular decision trees realized by ultrafast electronic spectroscopy
JF - Proceedings of the National Academy of Sciences
JO - Proc Natl Acad Sci USA
DO - 10.1073/pnas.1314978110
SP - 201314978
AU - Fresch, Barbara
AU - Hiluf, Dawit
AU - Collini, Elisabetta
AU - Levine, R. D.
AU - Remacle, F.
Y1 - 2013/09/11
UR - http://www.pnas.org/content/early/2013/09/10/1314978110.abstract
N2 - One possible way to reduce the physical dimensions of a computing node is to instruct a molecule to evaluate a complicated logic function. This is even more so if several such functions are processed in parallel. The interaction between light and matter is a suitable route because it is bilinear, depending on both the properties of the laser and of the molecule; the outcome depends on the initial state of the molecule and there can be more than one distinct path leading to the readout signal. Two-dimensional photon spectroscopy is shown to have four paths originating from each interaction, thereby enabling, as shown in SI Text, quaternary logic. In the main text, we discuss the simpler case of binary logic.The outcome of a light–matter interaction depends on both the state of matter and the state of light. It is thus a natural setting for implementing bilinear classical logic. A description of the state of a time-varying system requires measuring an (ideally complete) set of time-dependent observables. Typically, this is prohibitive, but in weak-field spectroscopy we can move toward this goal because only a finite number of levels are accessible. Recent progress in nonlinear spectroscopies means that nontrivial measurements can be implemented and thereby give rise to interesting logic schemes where the outputs are functions of the observables. Lie algebra offers a natural tool for generating the outcome of the bilinear light–matter interaction. We show how to synthesize these ideas by explicitly discussing three-photon spectroscopy of a bichromophoric molecule for which there are four accessible states. Switching logic would use the on–off occupancies of these four states as outcomes. Here, we explore the use of all 16 observables that define the time-evolving state of the bichromophoric system. The bilinear laser–system interaction with the three pulses of the setup of a 2D photon echo spectroscopy experiment can be used to generate a rich parallel logic that corresponds to the implementation of a molecular decision tree. Our simulations allow relaxation by weak coupling to the environment, which adds to the complexity of the logic operations.
ER -