APS Physics Tip Sheet – May 6, 2014
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Lasers That Mimic Nerve Cells
Researchers have engineered semiconductor lasers that behave like nerve cells and that could be used to build computing structures based on neural circuits.
The brain’s information processing ability has inspired researchers to build computing architectures from building blocks that behave like neurons. To accurately mimic neural behavior, these individual units should exhibit similar characteristics: neurons respond to small stimuli with small, linear responses, and to large stimuli—above a critical threshold—with large, nonlinear responses. Essential to their operation is a so-called “refractory period” following the nonlinear events, during which any response is temporarily inhibited. Researchers from France have now engineered micropillar semiconductor lasers that can reproduce such refractory behavior and thus could form the basis of neuron-like optical computing architectures.
* F. Selmi, Sylvain Barbay (contact author), et al., “Relative refractory period in an excitable semiconductor laser,” Physical Review Letters(expected publication date: May 07)
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The Dark Side of the Higgs
The decay of the Higgs boson into “invisible particles” delivers no evidence of physics beyond the standard model, putting new limits on dark matter theories.
The recently discovered Higgs boson may act as a link between particles we are familiar with and particles that have so far avoided detection, such as dark matter. To investigate this possibility, the ATLAS collaboration (one of the two groups that discovered the Higgs) has searched through data from the Large Hadron Collider (LHC) for events where a Higgs boson decays into “invisible particles,” like neutrinos or dark matter particles. Such particles would leave no trace in the LHC’s detectors, but their presence could be inferred by analyzing the collision products. The researchers found that the frequency of these invisible decays does not exceed values predicted by the standard model of particle physics. They use this result to place the strongest limits to date on the strength with which Higgs bosons may interact with dark matter particles.
* ATLAS Collaboration (contact: atlas.publications@cern.ch), “Search for invisible decays of a Higgs boson produced in association with a Z boson in ATLAS,” Physical Review Letters (expected publication date: May 8)
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An Entanglement Laser Pointer
One of the main challenges for future quantum information technologies is the miniaturization and integration of components such as sources of entangled photon pairs. A research team in France has now built the first electrically powered semiconductor source of photon pairs. The scheme is much more compact than existing schemes and may be easily integrated into a fiber-optic communications network.
* F. Boitier, Sara Ducci (contact author) et al., “An electrically injected photon-pair source at room temperature,” Physical Review Letters(expected publication date: May 7)
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Journal articles and preprints are available to journalists on request.
Matteo Rini, PhD
Deputy Editor, Physics
