Physics News of the Week: Quantum Strangeness

| January 26, 2015 | 0 Comments

Another great week of winter has passed and it’s time to take a look at some of top research done last week. Here are the top 3 news stories, plus some additional links. If you would like to receive these news straight to your email box, register for our email newsletter.

1. Atoms Can be at Two Places at Once (Jan 20)

In the world of quantum mechanics, at least according to certain interpretations, an electron can be at two different positions at the same time. Everybody, who has ever read a popular science book on quantum mechanics knows this. But what about macroscopic objects? Surely a soccer ball does not fly towards the goalkeeper in two different paths simultaneously. But why is it so? Scientists from the University of Bonn have recently taken up this abstract question.

According to Dr. Andrea Alberti from Bonn, in order to answer the posed question we need to look at two different interpretations: “Quantum mechanics allows superposition states of large, macroscopic objects. But these states are very fragile, even following the football with our eyes is enough to destroy the superposition and makes it follow a definite trajectory. But it could also be because footballs obey completely different rules than those applying for single atoms,” Alberti commented. To compare these interpretations experimentally, physicists at Bonn had come up with an experimental scheme. With two optical tweezers they grabbed a single Caesium atom and pulled it in two opposing directions. In the macro-realist’s world the atom would then be at only one of the two final locations.  Quantum-mechanically, the atom would instead occupy a superposition of the two positions. The experiment confirmed that the atom has indeed taken different paths at the same time.2pmVn6bZ4mJY9Mx1VXoRZjl72eJkfbmt4t8yenImKBVvK0kTmF0xjctABnaLJIm9

2. Black Holes in Gravitational Theories with Unbounded Speed of Propagation (Jan 23)

Lorentz invariance (LI) is a cornerstone of modern physics, and strongly supported by all experiments up to date. Nevertheless, there are theoretical reasons why it would be interesting to explore the implications of broken invariance. In particular, our understanding of space-times at Plank scale is still highly limited, and the renomalizability and unitarity of gravity often lead to the violation of LI.

An example of a theory violating LI is the Horava theory of quantum gravity, which can include higher-dimensional spatial derivative operators, so that the ultra-violet (UV) behavior is dramatically improved. However, if LI is broken different species of particles can travel with speeds larger that the speed of light. Such a prediction would lead to a conclusion that black holes cannot form. According to this new report, however, black holes can form under certain circumstances.

3. Physicists Find a New Way to Slow the Speed of Light (Jan 23)

A team of physicists working at the University of Glasgow has found a way to slow the speed of light that does not involve running it through a medium such as glass or water. Instead, as they explain in their paper published in the journal Science, they caused a change in the speed by first running it through a mask, which changed its shape. The results have deep implications in astronomical and lab measurements involving light. To find out more, read the report here.

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