On Hot Entanglement….

Quantum Entanglement of 15 Trillion Atoms at 450 Kelvin With “Surprising Results”

Cloud of Atoms with Pairs of Entangled Particles

Artistic illustration of a cloud of atoms with pairs of particles entangled between each other, represented by the yellow-blue lines. Credit: © ICFO

Quantum entanglement is a process by which microscopic objects like electrons or atoms lose their individuality to become better coordinated with each other. Entanglement is at the heart of quantum technologies that promise large advances in computing, communications and sensing, for example detecting gravitational waves.

Entangled states are famously fragile: in most cases even a tiny disturbance will undo the entanglement. For this reason, current quantum technologies take great pains to isolate the microscopic systems they work with, and typically operate at temperatures close to absolute zero. The ICFO team, in contrast, heated a collection of atoms to 450 Kelvin, millions of times hotter than most atoms used for quantum technology. Moreover, the individual atoms were anything but isolated; they collided with each other every few microseconds, and each collision set their electrons spinning in random directions.

The researchers used a laser to monitor the magnetization of this hot, chaotic gas. The magnetization is caused by the spinning electrons in the atoms, and provides a way to study the effect of the collisions and to detect entanglement. What the researchers observed was an enormous number of entangled atoms — about 100 times more than ever before observed. They also saw that the entanglement is non-local — it involves atoms that are not close to each other. Between any two entangled atoms there are thousands of other atoms, many of which are entangled with still other atoms, in a giant, hot and messy entangled state.

Glass Cell Rubidium Metal

Picture of the glass cell that where the rubidium metal is mixed with nitrogen gas and heated up to 450 degrees Kelvin. At that high temperature, the metal vaporizes, creating free rubidium atoms that diffuse around inside the cell. Credit: © ICFO

What they also saw, as Jia Kong, first author of the study, recalls, “is that if we stop the measurement, the entanglement remains for about 1 millisecond, which means that 1000 times per second a new batch of 15 trillion atoms is being entangled. And you must think that 1 ms is a very long time for the atoms, long enough for about fifty random collisions to occur. This clearly shows that the entanglement is not destroyed by these random events. This is maybe the most surprising result of the work.”

The observation of this hot and messy entangled state paves the way for ultra-sensitive magnetic field detection. For example, in magnetoencephalography (magnetic brain imaging), a new generation of sensors uses these same hot, high-density atomic gases to detect the magnetic fields produced by brain activity. The new results show that entanglement can improve the sensitivity of this technique, which has applications in fundamental brain science and neurosurgery.

As ICREA Prof. at ICFO Morgan Mitchell states, “this result is surprising, a real departure from what everyone expects of entanglement.” He adds “we hope that this kind of giant entangled state will lead to better sensor performance in applications ranging from brain imaging to self-driving cars to searches for dark matter.”

A Spin Singlet and QND

A spin singlet is one form of entanglement where the multiple particles’ spins–their intrinsic angular momentum–add up to 0, meaning the system has zero total angular momentum. In this study, the researchers applied quantum non-demolition (QND) measurement to extract the information of the spin of trillions of atoms. The technique passes laser photons with a specific energy through the gas of atoms. These photons with this precise energy do not excite the atoms but they themselves are affected by the encounter. The atoms’ spins act as magnets to rotate the polarization of the light. By measuring how much the photons’ polarization has changed after passing through the cloud, the researchers are able to determine the total spin of the gas of atoms.

The SERF regime

Current magnetometers operate in a regime that is called SERF, far away from the near absolute zero temperatures that researchers typically employ to study entangled atoms. In this regime, any atom experiences many random collisions with other neighboring atoms, making collisions the most important effect on the state of the atom. In addition, because they are in a hot medium rather than an ultracold one, the collisions rapidly randomize the spin of the electrons in any given atom. The experiment shows, surprisingly, that this kind of disturbance does not break the entangled states, it merely passes the entanglement from one atom to another.

Reference:”Measurement-induced, spatially-extended entanglement in a hot, strongly-interacting atomic system” by Jia Kong, Ricardo Jiménez-Martínez, Charikleia Troullinou, Vito Giovanni Lucivero, Géza Tóth and Morgan W. Mitchell, 15 May 2020, Nature Communications.
DOI: 10.1038/s41467-020-15899-1

from:    https://scitechdaily.com/quantum-entanglement-of-15-trillion-atoms-at-450-kelvin-with-surprising-results/

Dealing With the Plastic Problem

New Studies Raise Hopes for Making Plastic Safer

Plastic debris in the stomach of an albatross chick. (Chris Jordan, USFWS / Wikimedia Commons)

The good news is that safe plastic is not an impossible dream: novel ways to tackle the tide of discarded material engulfing the planet are under development.

One scheme absorbing US chemists will turn natural waste into natural polymers. Some day the crabmeat sandwiches in your packed lunch could be safely wrapped in transparent packaging fashioned from crushed crab shells and discarded wood chippings.

The protective wrapping would have all the strength of the polyethylene-based packaging that comes with millions of supermarket products, with one big difference. It will decompose naturally. Polyethylene is the most common form of plastic, with global demand expected to reach almost 100m tonnes in 2018.

Plastic polymer compounds are products of the petroleum industry and have changed lives the world over. But because plastic polymers are all but indestructible, they also promise to change lives everywhere for the worse, as empty plastic cups, soft drinks bottles and supermarket shopping bags amass in the oceans, along shorelines, and in what would otherwise be natural wilderness.

Researchers have already warned that long after humanity becomes extinct, a geological stratum rich in fragmented plastic toys, drinking straws and yoghurt pots could bear witness to the brief tenure of Homo sapiens.

Plastic detritus threatens to swamp the entire planet. Particles have been found in the Arctic ice, and plastic flotsam could carry dangerous infections to the most distant coral reefs.

But as the world’s nations falteringly begin to address the challenges of global warming and climate change, driven by profligate human use of fossil fuels, laboratories around the world have been working on possible solutions, both by finding ways to use energy more efficiently, and by exploiting natural wastes.

The latest study in ingenuity is described in the American Chemical Society’s journal ACS Sustainable Chemistry and Engineering.

Soil Additive

Researchers sprayed layers of the natural polymer chitin – the substance that provides the exoskeleton of the lobster or the locust – and the plant polymer cellulose to make a thin, flexible, transparent material that could one day replace PET, or polyethylene terephthalate. Cellulose is by far the most common natural polymer – unlike money, it really does grow on trees. Chitin may be the second most common: it is made by shellfish, insects and fungi.

But in the form of alternating layers, made by nanotechnologists – scientists who work in scales of a billionth of a metre – and then dried, the new product becomes strong, flexible and transparent, and something you could throw into the compost heap and watch turn back into nourishing soil.

Such a product is a long way from any commercial manufacture: a lot more needs to be achieved, and many hurdles have to be cleared. But such studies are once again evidence that the chemists and engineers are thinking hard.

“We have been looking at cellulose nanocrystals for several years and exploring ways to improve those for use in lightweight composites as well as food packaging, because of the huge market opportunity for renewable and compostable packaging, and how important food packaging overall is going to be as the population continues to grow,” said Carson Meredith, of Georgia Institute of Technology’s school of chemical and biomolecular engineering.

“Our material showed up a 67% reduction in oxygen permeability over some forms of PET, which means it could in theory keep foods fresher, longer.”

Tim Radford / Climate News Network

from:    https://www.truthdig.com/articles/there-is-a-way-to-make-plastic-safe/