Yin-Yang Entanglement, Biofriendly Viscosity, and LHC Trouble (Patreon)

A Yin-Yang-Shaped Photon Source Creates Confusion

A reconstructed signal with a Yin-Yang-shaped filter. Image credit: Zia et al., Nature Photonics, 2023.

It can be difficult to figure out the properties of a laser beam, and yet you need to know those properties if your experiments require high precision. Physicists from Canada and Spain have recently published a paper that makes the beam analysis easier, added a pretty image, and created a lot of confusion with this.

Their method works by overlaying an unknown signal with a known signal and then sending both into several optical components, notably a non-linear crystal and a beam splitter. This creates two outputs that can be analysed for interference. From this combined signal, one can then reconstruct the properties of the wave-function in the unknown beam. The method can effectively amplify details in the unknown signal so it has some advantages over a direct beam analysis.

As an example, they put a Yin-Yang-shaped filter on the laser beam they tried to reconstruct and demonstrated that the reconstruction worked. This is what is shown in the above image that you might have seen on social media last week. It does not show a single photon (but a reconstruction from many photons) and while the photons are also entangled, for the interference you just need them to be coherent. Press release here, paper here.

Viscosity is Bio-friendly…Who Knew?

A scientist at the Queen Mary University of London has shown that our universe is bio-friendly in a surprising way. For life to be possible, liquids should neither flow too easily nor too slowly, and in our universe, they do it just the right way. The flowing behaviour of liquids is quantified with the “viscosity” of a liquid. Honey has high viscosity. Superfluids (technically) have a viscosity of zero.

According to the new paper, a proper viscosity level is necessary for vital cell processes. For example, if the viscosity of water is too high, cellular processes such as protein folding and enzyme activity stop working. If it’s too low, cell membranes become useless. And while life on earth is based on water in particular, the paper's author claims these viscosity bounds need to be fulfilled by whatever liquid on which life elsewhere is based.

Viscosity is, of course, not a fundamental quantity, but ultimately derives from other, more fundamental constants – such as the masses of elementary particles and the strengths of their interactions – so any bound on the viscosity of water implicitly provides another constraint on the fundamental constants. Paper here.

Tree Falls on Power Line, Causes LHC Problems

Photo Credit: Romande Energie and CERN.

Early on July 17, a tree collapsed on power lines about 55 kilometres from CERN. It led to a chain reaction that resulted in the unplanned shut-down of the Large Hadron Collider (LHC).

After the power interruption, a safety system at CERN shut off the LHC beams. The magnets that guide the beam are cooled with liquid helium, and uncontrolled warming can greatly damage them. This is why the LHC has a “quench protection system” that, in the case of power supply problems, induces a controlled homogeneous warming. Unfortunately, in one instance, this didn’t work as desired, and mechanical stress created a leak between the cooling system and the magnet’s insulation. The damage is currently being repaired. Collisions are expected to start back up in early September. Read more about the event here and the repair process here.