# physics: SQUID, a probe at the boundary between 'quantum' and 'classic' worlds

<< A new device that relies on flowing clouds of ultracold atoms promises potential tests of the intersection between the weirdness of the quantum world and the familiarity of the macroscopic world we experience every day. The atomtronic Superconducting QUantum Interference Device (SQUID) is also potentially useful for ultrasensitive rotation measurements and as a component in quantum computers. >>

AA << created the device by trapping cold atoms in a sheet of laser light. A second laser intersecting the sheet "painted" patterns that guided the atoms into two semicircles separated by small gaps known as Josephson Junctions. When the SQUID is rotated and the Josephson Junctions are moved toward each other, the populations of atoms in the semicircles change as a result of quantum mechanical interference of currents through Josephson Junctions. By counting the atoms in each section of the semicircle, the researchers can very precisely determine the rate the system is rotating.>>

James Riordon. Atomtronic device could probe boundary between quantum, everyday worlds. Los Alamos National Laboratory. July 17, 2020.

https://phys.org/news/2020-07-atomtronic-device-probe-boundary-quantum.html

C. Ryu, E. C. Samson, M. G. Boshier. Quantum interference of currents in an atomtronic SQUID. Nat Commun 11, 3338. doi: 10.1038/ s41467-020-17185-6. Jul 3, 2020.

https://www.nature.com/articles/s41467-020-17185-6

# phys: bizarre, cosmic mysteries, when spin particles bump up from 1/2 to 3/2 and more

<< spin is essential when delving into virtually any topic governed by quantum mechanics (..) Yet after almost a century of playing a central role in quantum research, questions about spin remain. For example, why do all the elementary particles that we know about only have spin values of 0, 1/2, or 1? And what new behaviors might exist for particles with spin values greater than 1? The first question may remain a cosmic mystery, but there are opportunities to explore the second. (..)  In the past couple years, researchers have discovered materials in which electrons behave like their spin has been bumped up, from 1/2 to 3/2. (..)  (recently, AA) explored the new behaviors these spins might produce .>>

Bailey Bedford. Peeking into a world of spin-3/2 materials. Joint Quantum Institute. Apr 16, 2020.

https://phys.org/news/2020-04-peeking-world-spin-materials.html

AA << study, for the first time, the effects of strong short-range electron-electron interactions (..) (they) combine symmetry considerations and a perturbative renormalization group analysis to discern three interacting phases that are prone to emerge in the strongly correlated regime (..) (AA) find that symmetry breaking occurs at weaker coupling if the total monopole charge remains constant across the transition. >>

Igor Boettcher. Interplay of Topology and Electron-Electron Interactions in Rarita-Schwinger-Weyl semimetals. 

Phys. Rev. Lett. 124, 127602. Mar 27, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.127602