In this issue: Planet Search Finds No Dark-Matter Black Holes, Secure Quantum Commitment, A Single-Atom Switch, and More
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Planet Search Finds No Dark-Matter Black Holes
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(Image credit: NASA/Kepler mission/Wendy Stenzel)
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Using data from a planet-hunting mission, scientists place new limits on a supposed population of moon-sized black holes that could act as dark matter in our galaxy
According to recent theoretical studies, small, primordial black holes (PBHs) formed during the universe’s early expansion could be responsible for the gravitational effects attributed to dark matter. A team of researchers from the US and Taiwan has searched for PBHs using observations by Kepler - a NASA satellite designed to look for Earth-like planets orbiting other stars. Over 4 years, Kepler monitored ~150,000 stars in the Milky Way. If a primordial black hole passed in front of one of these stars, the star would become temporarily brighter due to the hole’s gravitational lensing. The analysis revealed no black-hole lensing events, ruling out the possibility that primordial black holes could account for a major fraction of the dark matter that is known to exist in our galaxy.
* Kim Griest (contact author), AM Cieplak, and MJ Lehner, “New limits on primordial black-hole dark matter from an analysis of Kepler source microlensing data”, Physical Review Letters (expected publication date: Oct 31)
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Secure Quantum Commitment
Researchers have demonstrated a secure quantum commitment scheme - a cryptographic protocol that allows one to commit to a chosen value, while keeping it secret until the value is revealed.
Secure commitment schemes could find use in bidding or voting systems, in which no one should learn anyone else's intent before an appointed time. Inspired by the success of quantum cryptography techniques like Quantum Key Distribution, researchers have turned to quantum mechanics to develop inherently secure commitment protocols. Some theoretical work seemed to demonstrate that a secure quantum commitment scheme was impossible, but according to a 2012 proposal, a solution could be found if relativistic effects were present. Now, a group of researchers from Switzerland, Singapore, the UK and Canada has experimentally realized this proposal. In an optical fiber link between Geneva and Singapore, the team showed that a committed bit could be kept secret for up to 15 milliseconds - a time that may be sufficient for high-speed applications such as stock trading.
* T Lunghi, Felix Bussières (contact author) et al, “Experimental bit commitment based on quantum communication and special relativity”, Physical Review Letters (expected publication date: Nov 1)
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A Single-Atom Switch
A research team at the Vienna Center for Quantum Science and Technology has demonstrated an optical switch made of a single rubidium atom placed in a microscopic cavity. Controlled by the atom position, the switch can be used to reroute optical signals from an optical fiber to different output fiber ports.
* D O’Shea, C Junge, J Volz, Arno Rauschenbeutel (contact author), “Fiber-optical switch controlled by a single atom”, Physical Review Letters (expected publication date: Nov 4)
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More from the APS Physics News Ticker:
- Twisting Ribbons: Researchers have developed a model that can be used to design devices made of elastic materials likegraphene sheets, semiconductor nanoribbons and biomaterials.
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Journal articles and preprints are available to journalists on request.
