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A New Card up Graphene’s Sleeve

Graphene is found to exhibit a magnetoresistance dwarfing that of all known materials at room temperature—a behavior that may lead to new magnetic sensors and help decipher the physics of strange metals.

One might expect that, two decades after its discovery, graphene would have exhausted its potential for surprises. But the thinnest, strongest, most conductive of all materials has now added another record to its tally. A collaboration that includes graphene’s codiscoverer and Nobel laureate Andre Geim of the University of Manchester, UK, reports that graphene can have a room-temperature magnetoresistance—a magnetic-field-induced change in electrical resistivity—that’s 100 times larger than that of any known material [1]. Graphene’s giant magnetoresistance could lead to novel magnetic-field sensors but also offer an experimental window into exotic quantum regimes of electrical conduction that might be related to the mysterious “strange metals.”

Magnetoresistance, which occurs both in bulk materials and multilayer structures, found a killer app in magnetic-field sensors such as those used to read data from magnetic memories. Researchers have long been interested in the limits of this phenomenon, which has led to discoveries of “giant,” “colossal,” and “extraordinary” forms of magnetoresistance. The associated materials exhibit resistivity changes of up to 1,000,000% when exposed to magnetic fields of several teslas (T). The largest effects, however, require extremely low temperatures that can only be reached with impractical liquid-helium cooling systems.

Heaviest Schrödinger cat achieved by putting a small crystal into a superposition of two oscillation states

Even if you are not a quantum physicist, you will most likely have heard of Schrödinger’s famous cat. Erwin Schrödinger came up with the feline that can be alive and dead at the same time in a thought experiment in 1935. The obvious contradiction—after all, in everyday life we only ever see cats that are either alive or dead—has prompted scientists to try to realize analogous situations in the laboratory. So far, they have managed to do so using, for instance, atoms or molecules in quantum mechanical superposition states of being in two places at the same time.

At ETH, a team of researchers led by Yiwen Chu, professor at the Laboratory for Solid State Physics, has now created a substantially heavier Schrödinger cat by putting a small crystal into a of two oscillation states. Their results, which have been published this week in the journal Science, could lead to more robust quantum bits and shed light on the mystery of why quantum superpositions are not observed in the macroscopic world.

In Schrödinger’s original , a cat is locked up inside a metal box together with a radioactive substance, a Geiger counter and a flask of poison. In a certain time-frame—an hour, say—an atom in the substance may or may not decay through a quantum mechanical process with a certain probability, and the decay products might cause the Geiger counter to go off and trigger a mechanism that smashes the flask containing the poison, which would eventually kill the cat.

Long-distance quantum teleportation enabled by multiplexed quantum memories

Quantum teleportation is a technique allowing the transfer of quantum information between two distant quantum objects, a sender and a receiver, using a phenomenon called quantum entanglement as a resource.

The unique feature of this process is that the actual information is not transferred by sending quantum bits (qubits) through a connecting the two parties; instead, the information is destroyed at one location and appears at the other one without physically traveling between the two. This surprising property is enabled by , accompanied by the transmission of classical bits.

There is a deep interest in quantum teleportation nowadays within the field of quantum communications and quantum networks because it would allow the transfer of between network nodes over very long distances, using previously shared entanglement.

Embracing variations: Physicists first to analyze noise in Lambda-type quantum memory

In the future, communications networks and computers will use information stored in objects governed by the microscopic laws of quantum mechanics. This capability can potentially underpin communication with greatly enhanced security and computers with unprecedented power. A vital component of these technologies will be memory devices capable of storing quantum information to be retrieved at will.

Virginia Lorenz, a professor of physics at the University of Illinois Urbana-Champaign, studies Lambda-type optical quantum , a promising technology that relies on light interacting with a large group of atoms. She is developing a device based on hot metallic vapor with graduate student Kai Shinbrough.

As the researchers work towards a practical device, they are also providing some of the first theoretical analyses of Lambda-type devices. Most recently, they reported the first variance-based sensitivity analysis describing the effects of experimental noise and imperfections in Physical Review A.

Experiments show that edges are not needed to realize an unusual quantum effect

RIKEN physicists have created an exotic quantum state in a device with a disk-like geometry for the first time, showing that edges are not required. This demonstration opens the way for realizing other novel electronic behavior. Their findings are published in Nature Physics.

Physics has long moved on from the three classic states of matter: solid, liquid and gas. A better theoretical understanding of quantum effects in crystals and the development of advanced experimental tools to probe and measure them has revealed a whole host of exotic states of matter.

A prominent example of this is the : a kind of crystalline solid that exhibits wildly different properties on their surfaces than in the rest of the material. The best-known manifestation of this is that conduct electricity on their surfaces but are insulating in their interiors.

Could Aluminum Nitride Produce Quantum Bits?

Quantum computers have the potential to break common cryptography techniques, search huge datasets and simulate quantum systems in a fraction of the time it would take today’s computers. But before this can happen, engineers need to be able to harness the properties of quantum bits or qubits.

Currently, one of the leading methods for creating qubits in materials involves exploiting the structural atomic defects in diamond. But several researchers at the University of Chicago and Argonne National Laboratory believe that if an analogue defect could be engineered into a less expensive material, the cost of manufacturing quantum technologies could be significantly reduced. Using supercomputers at the National Energy Research Scientific Computing Center (NERSC), which is located at the Lawrence Berkeley National Laboratory (Berkeley Lab), these researchers have identified a possible candidate in aluminum nitride. Their findings were published in Nature Scientific Reports.

“Silicon semiconductors are reaching their physical limits—it’ll probably happen within the next five to 10 years—but if we can implement qubits into semiconductors, we will be able to move beyond silicon,” says Hosung Seo, University of Chicago Postdoctoral Researcher and a first author of the paper.

Is Time Travel Possible In Our Universe?

The first 100 people to use code UNIVERSE at the link below will get 60% off of Incogni: https://incogni.com/universe.

Researched and Written by Colin Stuart.
Check out his superb Astrophysics for Beginners course here: https://www.colinstuart.net/astrophysics-course-for-beginner…on-online/

Edited by Manuel Rubio.
Narrated and Script Edited by David Kelly.
Thumbnail art by Ettore Mazza, the GOAT: https://www.instagram.com/ettore.mazza/?hl=en.
Animations by Jero Squartini https://fiverr.com/freelancers/jerosq.
Stock footage taken from Videoblocks and Artgrid, music from Epidemic Sound, Artlist, Silver Maple and Yehezkel Raz.
Space imagery also used from NASA and ESO.

Specific image credits:
AT Service via Wikimedia for images of Kip Thorne and Bryce DeWitt.
Massachusetts Institute of Technology, via Wikimedia Commons for the image of Bruno Rossi.

00:00 Introduction.
06:00 The Block Universe.
16:25 Visiting The Future.
27:00 Visiting The Past.
37:59 Time Streams.

#wormhole #quantum

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