Quantum-Dot Sources for Single Photons and Entangled Photon Pairs

Quantum dots show excellent promise as triggered sources of both single and polarization entangled photons for quantum information applications. Our recent progress developing nonclassical light sources with single quantum dots is presented in this paper. Following radiative emission of an exciton confined in a quantum dot, there is a finite delay before re-excitation can occur; this results in an anti-bunching of the photons emitted providing a source of single photons. Excitation of a quantum dot with two electrons and two holes leads to the emission of a pair of photons; we show here that, provided the spin splitting of the intermediate exciton state in the decay is erased, the photon pair is emitted in an entangled polarization state. The fidelity of this entangled state is shown to exceed 70%. Using quantum dots to generate quantum light allows contacts for electrical injection to be integrated into a compact and robust device. A cavity may also be integrated into the semiconductor structure to enhance the photon collection efficiency and control the recombination dynamics. We detail a process to form a submicrometer current aperture within an electrical device, allowing individual quantum dots to be addressed electrically in devices.     

Design, control, and energetic characterization of a solenoid-injected monopropellant-powered actuator

This paper describes a direct-injection configuration of a monopropellant-powered actuator that is intended to provide high-energy-density actuation for a self-powered position- or force-controlled human-scale robot. The proposed actuator is pressurized by a pair of solenoid injection valves (each of which control the flow of a monopropellant through a catalyst pack and directly into the respective side of a pneumatic-type cylinder), and depressurized via a three-way hot-gas proportional exhaust valve. A controller is described that coordinates the control of the two solenoid propellant injection valves, together with the control of the proportional hot-gas exhaust valve, in order to provide actuator force tracking. Experimental results are presented that validate the effectiveness of the force-control approach. Finally, energetic performance of the proposed actuator is experimentally assessed and shown to provide an energetic figure of merit, an order of magnitude greater than that of a battery-powered servomotor approach.     

System Level Design for System on a Chip

We present the systems requirements generation and executable specification capture of a single chip LAN Adapter for communicating using the IEEE 1394 Serial Bus Protocol. The requirements generation starts with high level performance simulation and then passes to an executable specification suitable for implementation using a hardware/software co-design tool. The reuse of pre-existing components is supported, as well as synthesis of the system interface, but only after much work is done to program the hardware/software co-design tool. The actual design flow described allows feedback among all design levels, e.g. from implementation up to requirements, throughout the process.