Friday, August 2, 2019

Quantum Darwinism Could Explain What Makes Reality Real

Contrary to popular belief, says physicist Adán Cabello,
“quantum theory perfectly describes the emergence of
the classical world.” Olena Shmahalo/Quanta Magazine

It’s not surprising that quantum physics has a reputation for being weird and counterintuitive. The process by which “quantumness” disappears into the environment is called decoherence. It’s a crucial part of the quantum-classical transition, explaining why quantum behavior becomes hard to see in large systems with many interacting particles.

To explain the emergence of objective, classical reality, it’s not enough to say that decoherence washes away quantum behavior and thereby makes it appear classical to an observer. Somehow, it’s possible for multiple observers to agree about the properties of quantum systems. Zurek, who works at Los Alamos National Laboratory in New Mexico, argues that two things must therefore be true.

First, quantum systems must have states that are especially robust in the face of disruptive decoherence by the environment. Zurek calls these “pointer states,” because they can be encoded in the possible states of a pointer on the dial of a measuring instrument. A particular location of a particle, for instance, or its speed, the value of its quantum spin, or its polarization direction can be registered as the position of a pointer on a measuring device. Zurek argues that classical behavior—the existence of well-defined, stable, objective properties—is possible only because pointer states of quantum objects exist. (Full story)

California earthquake: Scientists closer to predicting when the Big One will strike

California is a hotspot for seismic activity, and experts have been warning of a theoretical ‘Big One’ for some time. When the Big One strikes, it will devastate the Golden State – but scientists previously had no way of predicting when it will come. However, a new study has yielded some major results and it could be the key to forecasting a major earthquake in California.
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Scientists from the Los Alamos National Laboratory have analyzed a staggering 1.8 million minor earthquakes in California – many of which were below a magnitude one on the Richter scale.

The team found that a series of minor tremors preceded a “mainshock” in 72 percent of cases. (Full story)

Quantum computers to clarify the connection between the quantum and classical worlds

Los Alamos National Laboratory scientists have developed a new quantum computing algorithm that offers a clearer understanding of the quantum-to-classical transition, which could help model systems on the cusp of quantum and classical worlds, such as biological proteins, and also resolve questions about how quantum mechanics applies to large-scale objects.

"The quantum-to-classical transition occurs when you add more and more particles to a quantum system," said Patrick Coles of the Physics of Condensed Matter and Complex Systems group at Los Alamos National Laboratory, "such that the weird quantum effects go away and the system starts to behave more classically. For these systems, it's essentially impossible to use a classical computer to study the quantum-to-classical transition. We could study this with our algorithm and a quantum computer consisting of several hundred qubits, which we anticipate will be available in the next few years based on the current progress in the field." (Full story)

Melting ice may change shape of Arctic river deltas

Kolyma Delta, Russia. Landsat natural color
satellite image. May 30, 2013. Credit: USGS

Thawing ice cover and easily erodible permafrost may destabilize Arctic river deltas, according to new research. A new study in the AGU journal Geophysical Research Letters finds sea ice and permafrost both act to stabilize channels on Arctic river deltas.

"Your channels tend to stay in one place when you have really thick ice or when you have permafrost that's really hard to erode," said Rebecca Lauzon, environmental educator at the Rochester Museum and Science Center's Cumming Nature Center in New York and the lead author of the new study.

Lauzon, who was working an internship at Los Alamos National Laboratory during the time of the research, and her co-authors, created two versions of a model: One to predict the effects that ice thickness might have on Arctic river deltas and another to predict the effects of permafrost strength. (Full story)

Numerical Model Pinpoints Source of Pre-Cursor to Seismic Signals

Numerical simulations have pinpointed the source of acoustic signals emitted by stressed faults in laboratory earthquake machines. The work further unpacks the physics driving geologic faults, knowledge that could one day enable accurately predicting earthquakes.

“Previous machine-learning studies found that the acoustic signals detected from an earthquake fault can be used to predict when the next earthquake will occur,” said Ke Gao, a computational geophysicist in the Geophysics group at Los Alamos National Laboratory. “This new modeling work shows us that the collapse of stress chains inside the earthquake gouge emits that signal in the lab, pointing to mechanisms that may also be important in Earth.”

Stress chains are bridges composed of grains that transmit stresses from one side of a fault block to the other. (Full story)