Search

A source of triggered entangled photon pairs is a key component in quantum information science (1); it is needed to implement functions such as linear quantum computation (2), entanglement swapping (3) and quantum teleportation (4). Generation of polarization entangled photon pairs can be obtained through parametric conversion in nonlinear optical media (5-7) or by making use of the radiative decay of two electron-hole pairs trapped in a semiconductor quantum dot (8-11). Today, these sources operate at a very low rate, below 0.01 photon pairs per excitation pulse, which strongly limits their applications. For systems based on parametric conversion, this low rate is intrinsically due to the Poissonian statistics of the source (12). Conversely, a quantum dot can emit a single pair of entangled photons with a probability near unity but suffers from a naturally very low extraction efficiency. Here we show that this drawback can be overcome by coupling an optical cavity in the form of a 'photonic molecule' (13) to a single quantum dot. Two coupled identical pillars--the photonic molecule--were etched in a semiconductor planar microcavity, using an optical lithography method (14) that ensures a deterministic coupling to the biexciton and exciton energy states of a pre-selected quantum dot. The Purcell effect ensures that most entangled photon pairs are emitted into two cavity modes, while improving the indistinguish ability of the two optical recombination paths (15,16). A polarization entangled photon pair rate of 0.12 per excitation pulse (with a concurrence of 0.34) is collected in the first lens. Our results open the way towards the fabrication of solid state triggered sources of entangled photon pairs, with an overall (creation and collection) efficiency of 80%., To date, most quantum information and communication protocols necessitating entangled photon pairs have been realized using sources based on parametric down-conversion (2-7). These sources present Poissonian statistics: the probability that [...]

A brief theory and simulation overview for the purpose of design is presented with examples applies to modeling the physical properties, behavior, and phenomena of nanomaterial. This review paper constructs perspectives that consider coupling traditional domains of simulation by novel pathways to produce accurate representations of nanomaterial properties, behavior and phenomena. It is all about size scaling and how different approaches are able to simulate, integrate or simply pass the baton to the next level of complexity. In macroscopic world, the atomic or molecular information alone may not be directly useful. Nor is the bulk information useful in the microscopic world without intimate knowledge of molecular makeup. Therefore, when designing Nanomaterials, knowledge of properties spanning the complete range of size is the prerequisite of a recommended self-consistent approach. In fact, regarding applications in both industry and academia, the simulation first approach often can lead to great savings in time. This review paper focuses mostly on optical and electronic properties but a section is added that provides a segue into mechanical properties for future consideration. [ABSTRACT FROM AUTHOR]