Molecular arrays for dipole-based quantum information processing

University Of Connecticut, Storrs CT

Investigators

Abstract

As the field of quantum information processing (QIP) matures, so do its goals. In particular, we are looking for more realistic and better scalable systems, for novel areas of application and stronger crossfertilization with other areas in physics. In this proposal, we are addressing all of these goals. We propose to deepen and expand our investigation of polar molecules for QIP, specifically with a view towards feasibility, scalability, and connection with novel solid state and hybrid systems. We want to explore similar setups for efficient deterministic optical quantum computing systems that also could be used for efficient switches and transistors. First, we want to expand the idea of using single polar molecules for qubits. Polar molecules are ideal because of both recent fast progress in cooling and trapping promising similar densities as neutral atoms and of ion-like ease of manipulation. We described a deterministic and robust scheme where we can switch molecular dipole moments on and off using the rich level hierarchies in molecules. Here, we want to suggest, (i) generalized criteria for polar molecule-based QIP, (ii) the use of solid state rare gas matrices as an ideal and novel architecture in which molecules can be stored very close and with nearly no relative distance uncertainties, thus maximizing the potential of the dipole-dipole interaction even beyond nearest-neighbor interactions, (iii) a hybrid-type nano-fiber/molecular trap design to both trap and couple the molecules, potentially on a so-called ?molecular chip. The objective of the second part of the proposal is to introduce dipolar arrays as tools for deterministic optical quantum computation. The idea of this is to treat photons as qubits. Since photons do not interact directly, a non-linearity has to be introduced in order to create a two-qubit gate. We propose to create singlephoton nonlinearities by sending dark-state polaritons, photon molecule coupled excitations, through a dipolar medium subject to dipole-dipole interactions. While propagating, the photons thus accumulate a nonlinear phase shift that can be interpreted as a phase gate. We propose to (i) describe in detail the process including interrelation between density, propagation length, coupling, and dipole-dipole interaction strength in order to create an efficient phase gate; (ii) to give an overview over the most important decoherence sources, such as non-symmetric excitations and phonons and their typical strengths for particular setups; (iii) in order to battle decoherence to investigate the possibility of using so-called ?many-body protected manifolds? which introduce a bias between symmetric and non-symmetric state manifolds and thus mitigate phonon decay; (iv) to study optimal dimensionality and geometry and connect these with similar architectures as suggested in the first part of the proposal; and (v) to give an outlook to novel solid state setups such as Si surface quantum dots and semiconductor bound excitons in connection with the proposed idea.