16,980 research outputs found
Abating exhaust noises in jet engines
A noise abating improvement for jet engines including turbojets, turbofans, turboprops, ramjets, scramjets, and hybrid jets is introduced. A provision is made for an apparatus in the primary and/or secondary flow streams of the engines; the apparatus imparts to the exhaust gases a component rotation or swirl about the engine's longitudinal axis. The rotary component in the exhaust gases causes a substantial suppression of sound energy build up normally produced by an axial flow exhaust system
Third Conference on Sonic Boom Research
Prediction methods for sonic boom generation and propagation with overpressure minimization in supersonic transport design and operatio
All-Optical Depletion of Dark Excitons from a Semiconductor Quantum Dot
Semiconductor quantum dots are considered to be the leading venue for
fabricating on-demand sources of single photons. However, the generation of
long-lived dark excitons imposes significant limits on the efficiency of these
sources. We demonstrate a technique that optically pumps the dark exciton
population and converts it to a bright exciton population, using intermediate
excited biexciton states. We show experimentally that our method considerably
reduces the DE population while doubling the triggered bright exciton emission,
approaching thereby near-unit fidelity of quantum dot depletion.Comment: 5 pages, 3 figure
Determinisitic Writing and Control of the Dark Exciton Spin using Short Single Optical Pulses
We demonstrate that the quantum dot-confined dark exciton forms a long-lived
integer spin solid state qubit which can be deterministically on-demand
initiated in a pure state by one optical pulse. Moreover, we show that this
qubit can be fully controlled using short optical pulses, which are several
orders of magnitude shorter than the life and coherence times of the qubit. Our
demonstrations do not require an externally applied magnetic field and they
establish that the quantum dot-confined dark exciton forms an excellent solid
state matter qubit with some advantages over the half-integer spin qubits such
as the confined electron and hole, separately. Since quantum dots are
semiconductor nanostructures that allow integration of electronic and photonic
components, the dark exciton may have important implications on implementations
of quantum technologies consisting of semiconductor qubits.Comment: Added two authors, minor edits to figure captions, expanded
discussion of dark exciton eigenstate
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