The latest in Ph-word: January 2020

Starting with short space news, a second exoplanet seems to have been discovered orbiting Alpha Centauri. And another one at a hundred light-years away is the first exoplanet found to have similar conditions to earth’s (similar size and such a distance from its star that permits liquid water). Meanwhile, just outside the solar system Voyager 2 had a malfunction that led to high electricity consumption and to its scientific instruments shutting down; NASA has started dealing with the issue, in an effort to make power from the craft’s radioactive source last as long as possible, but faces the fact that each command now needs 17 hours to reach it.

Entanglement in space

The University of Science and Technology in Hefei, China, created the first portable ground station that can communicate with a “quantum encryption satellite”. And two separate things have shock potential in this sentence.

The first is clearly the quantum encryption part. Q-encryption relies on the use of pairs of “entangled photons”. These two chunks of light are produced together in a way that makes their characteristics connected with each other’s. The photons are then transmitted to different labs. Now, the moment that an entangled characteristic of one of them is first measured, its value for the other photon is automatically fixed. This means that both labs can know the measured value and that none else can.

If this is repeated with a few more pairs each lab has a sequence of numbers that taken together form a “key”, a “sentence” that can be used in cryptography to encode and decode messages, leading to the most secure communications known to humankind.

(Incidentally, if you were confused by how measuring one photon fixed the other one automatically, be assured that you are in good company – that is, if you happen to think that every physicist is good company.)

For the record, please note that contrary to what is often written, all this has nothing to do with either quantum computing or, god forbid, teleportation. Also, note that this process has already taken place in several labs in the last years, with the record for distance held by the satellite Mozi which transmitted entangled pairs to labs separated by 1,200 kilometers in 2017. It’s actually the same satellite that the new portable station will be using.

Going to the second source of shock potential in this piece of news, it’s actually future-shock potential: the development of the station was motivated by two chinese banks which are already using quantum key cryptography and want to make it more accessible regardless of a branch’s place on the map.

Violation under ground

In the last six years or so, only one of the experiments using the Large Hadron Collider has been making serious headlines from time to time. This is the LHCb experiment and the reason is that it is built for dealing with one of particle physics’ open mysteries: CP-violation.

The Ph-word has written about CP-violation before, so allow me to just link to that old piece (uploaded recently as a blog post). The news is that LHCb remeasured it in the activity of B-meson particles, five years after the previous result, with all the added benefits of loads of data gathered in the meantime.

The update is, like always, compatible with the theory of the Standard Model. But the abundance of data reduced one annoying thing: the uncertainty surrounding the mathematical models of what really happens between the quarks making up the B-mesons.

What’s the problem with these models? It’s that the strong nuclear force (holding quarks together in protons, neutrons, B-mesons and others) is hard to work out mathematically, as compared say to electromagnetism or to the weak nuclear force. Its models are rather baroque and always “under construction”, as they keep getting pimped by newer experiments like in the case at hand.

All in all, LHCb added precision to the previous results and improved the modeling of the strong force which will benefit future calculations and measurements. By the way, expect many of those, as people always hope to pinpoint for good the CP-violation inherent to the Standard Model and, one day, find some extra one coming from yet-unknown physics.

It wasn’t a spectacular month but it wasn’t a bad one either. So, which of the news attracted your attention more? (Personally, that would be the Voyager and the q-station pieces.)

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