Here’s another short overview of the most eye-catching news from last week. This time, the news titles include another big test for Einstein’s theory or general relativity and another closure of one of Bell loopholes. If you would like to receive these news straight to your email, please register to our email newsletter.
1. Another “Bell” Loophole Closed for Photons (April 23)
The famous Bell inequalities concern measurements and their effects on a pair of entangled particles. The inequalities assume that each quantum object has a well-defined state that accounts for all its measurable properties and that distant objects do not exchange information faster than the speed of light. By investigating the implications of these inequalities, experimental physicists can test the realism and locality in quantum mechanics. However, in the experimental tests of Bell’s theorem, there may be problems of experimental design or set-up that affect the validity of the experimental findings. These problems are often referred to as “loopholes”.
This week, the third and final loophole in an important test of the quantum nature of photons has been closed by an international team of physicists. The “fair sampling” loophole, which says that classical effects could be responsible for the measured correlations between entangled pairs of photons, was closed by Anton Zeilinger, Marissa Giustina and colleagues at the University of Vienna. Read the full report here.
Another Bell “loophole” closed
2. A New Matter-Antimatter Difference Observed at the LHC (April 24)
A new paper was submitted this week to Physical Review Letters on the first observation of matter-antimatter asymmetry in the decays of the particle known as the B0s — only the fourth subatomic particle known to exhibit such behaviour. The importance of this discovery comes from the fact that by studying subtle differences in the behaviour of particles and antiparticles, experiments at the LHC are seeking to cast light on the dominance of matter over antimatter in our universe. Read the full report here.
3. Einstein’s Theory of Gravity Overcomes Another Challenge (April 25)
Einstein’s theory of general relativity, which describes the interactions of masses and energy with space-time, is expected to break down under extreme conditions. Such conditions could manifest close to a massive black hole or, as scientists believed, between two massive stars orbiting each other. Such a system of stars has recently been studied by the scientists at the Max Planck institute in Germany. A massive stellar pair of stars nearly 7,000 light-years away from Earth has provided physicists an opportunity to study the nature of gravity. In such a system of stars, the orbits decay and gravitational waves are emitted, carrying energy from the system. By very precisely measuring the time of arrival of the pulsar’s radio pulses, astronomers can determine the amount of gravitational radiation emitted. And this data can then be used to test both Einstein’s theory and some alternative theories of gravity.
“We thought this system might be extreme enough to show a breakdown in General Relativity, but instead, Einstein’s predictions held up quite well,” said Paulo Freire, of the Max Planck Institute for Radioastronomy in Germany. Read the full report here.
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