3,269 research outputs found
Cryogenic spectroscopy of ultra-low density colloidal lead chalcogenide quantum dots on chip-scale optical cavities towards single quantum dot near-infrared cavity QED
We present evidence of cavity quantum electrodynamics from a sparse density
of strongly quantum-confined Pb-chalcogenide nanocrystals (between 1 and 10)
approaching single-dot levels on moderately high-Q mesoscopic silicon optical
cavities. Operating at important near-infrared (1500-nm) wavelengths, large
enhancements are observed from devices and strong modifications of the QD
emission are achieved. Saturation spectroscopy of coupled QDs is observed at
77K, highlighting the modified nanocrystal dynamics for quantum information
processing.Comment: * new additional figures and text * 10 pages, 5 figure
Patching Neural Barrier Functions Using Hamilton-Jacobi Reachability
Learning-based control algorithms have led to major advances in robotics at
the cost of decreased safety guarantees. Recently, neural networks have also
been used to characterize safety through the use of barrier functions for
complex nonlinear systems. Learned barrier functions approximately encode and
enforce a desired safety constraint through a value function, but do not
provide any formal guarantees. In this paper, we propose a local dynamic
programming (DP) based approach to "patch" an almost-safe learned barrier at
potentially unsafe points in the state space. This algorithm, HJ-Patch, obtains
a novel barrier that provides formal safety guarantees, yet retains the global
structure of the learned barrier. Our local DP based reachability algorithm,
HJ-Patch, updates the barrier function "minimally" at points that both (a)
neighbor the barrier safety boundary and (b) do not satisfy the safety
condition. We view this as a key step to bridging the gap between
learning-based barrier functions and Hamilton-Jacobi reachability analysis,
providing a framework for further integration of these approaches. We
demonstrate that for well-trained barriers we reduce the computational load by
2 orders of magnitude with respect to standard DP-based reachability, and
demonstrate scalability to a 6-dimensional system, which is at the limit of
standard DP-based reachability.Comment: 8 pages, submitted to IEEE Conference on Decision and Control (CDC),
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