Massively parallel classical logic via coherent dynamics of an ensemble of quantum systems with dispersion in size

peer reviewedThere is a worldwide effort toward quantum technology. Information processing, sensing, communication, and related areas are getting much of the attention. The advantages offered by the quantum domain are well recognized and acclaimed. Proposed implementations rely on systems operating at rather low temperatures and on the need to isolate the system from outside sources of noise. We discuss a theoretical scheme that suggests operating with a classical collection of quantum systems. An experimental demonstration of the principle is available. The ensemble is an array of size-disordered quantum dots addressed and probed by laser pulses. The algebraic approach encodes information in the coherences between quantum levels of the dots and demonstrates resilience to size disorder.Quantum parallelism can be implemented on a classical ensemble of discrete level quantum systems. The nanosystems are not quite identical, and the ensemble represents their individual variability. An underlying Lie algebraic theory is developed using the closure of the algebra to demonstrate the parallel information processing at the level of the ensemble. The ensemble is addressed by a sequence of laser pulses. In the Heisenberg picture of quantum dynamics the coherence between the N levels of a given quantum system can be handled as an observable. Thereby there are N2 logic variables per N level system. This is how massive parallelism is achieved in that there are N2 potential outputs for a quantum system of N levels. The use of an ensemble allows simultaneous reading of such outputs. Due to size dispersion the expectation values of the observables can differ somewhat from system to system. We show that for a moderate variability of the systems one can average the N2 expectation values over the ensemble while retaining closure and parallelism. This allows directly propagating in time the ensemble averaged values of the observables. Results of simulations of electronic excitonic dynamics in an ensemble of quantum dot (QD) dimers are presented. The QD size and interdot distance in the dimer are used to parametrize the Hamiltonian. The dimer N levels include local and charge transfer excitons within each dimer. The well-studied physics of semiconducting QDs suggests that the dimer coherences can be probed at room temperature.There are no data underlying this work.MONACOM