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Category: particle physics

Fifty-five years ago, Yuri Gagarin rocketed into orbit and began to break our bonds to our planet. To mark the occasion, the nonprofit Breakthrough Institute just announced plans to free us from an even more formidable set of bonds and send a fleet of small spacecraft beyond our solar system, off to the stars. News of the ‘Breakthrough Starshot’ plan was met with great enthusiasm, but also with more than a little skepticism. The distance between stars is vast. Our closest neighbour, the Alpha Centauri system, is 4.4 light years away – roughly 25 trillion miles. The Voyager 1 spacecraft, the fastest object ever created by humans, would take 70,000 years to travel that far. Many reporters greeted the Breakthrough Starshot as an idea grounded more in fantasy than in reality.

The reaction was understandable. All previous plans for interstellar flight relied on non-existent or impractical technologies such as antimatter, wormholes and warp drives. But now we have a concrete path forward, which I have published in detail. It is possible to begin the journey to the stars today.

Drawing on recent advances in photonics and electronics, we could use arrays of lasers to accelerate miniature probes (the size and mass of a semiconductor wafer, weighing less than one ounce) to unprecedented velocities. Particles of light, or photons, have no rest mass but they carry energy and momentum. Just as a sailboat can be propelled by the wind, light sails can ride the momentum of photons by reflecting a wind of intense laser light. We call such focused beams of light ‘directed energy’.

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Nice.

Sandia National Laboratories has taken a first step toward creating a practical quantum computer, able to handle huge numbers of computations instantaneously.

Here’s the recipe:

A “donor” atom propelled by an is inserted very precisely in microseconds into an industry-standard silicon substrate.

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The collapse of a trapped ultracold magnetic gas is arrested by quantum fluctuations, creating quantum droplets of superfluid atoms.

Macroscopic implosions of quantum matter waves have now been halted by quantum fluctuations. The quantum wave in question is an atomic Bose-Einstein condensate (BEC), a quantum state with thousands to tens of millions of atoms in an ultracold gas all sharing the same macroscopic wave function. Attractive atomic interactions can cause BECs to collapse in spectacular ways, in what’s been termed a “bosenova,” a lighthearted allusion to a supernova explosion [1]. Tilman Pfau and colleagues from the University of Stuttgart, Germany, have shown that for BECs made of dysprosium, whose bosonic isotopes are among the most magnetic atoms in the periodic table, long-range dipole-dipole interactions between these neutral atoms create a totally new phenomenon: the arrested collapse of a quantum magnetic fluid, called a quantum ferrofluid [2, 3]. Such a ferrofluid relies crucially on the strong dipolar interactions in the dysprosium gas.

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Finally, some well deserved recogonition to Argonne Natl. Labs in their efforts on QC with the Univ. Of Chicago.

If biochemists had access to a quantum computer, they could perfectly simulate the properties of new molecules to develop novel drugs in ways that would take the fastest existing computers decades.

Electrons represent an ideal quantum bit, with a “spin” that when pointing up can represent a 0 and down can represent a 1. Such bits are small—even smaller than an atom—and because they do not interact strongly, they can remain quantum for long periods. However, exploiting electrons as qubits also poses a challenge because they must be trapped and manipulated. Which is exactly what David Schuster, assistant professor of physics, and his collaborators at UChicago, Argonne National Laboratory and Yale University have done.

“A key aspect of this experiment is that we have integrated trapped electrons with more well-developed superconducting quantum circuits,” said graduate student Ge Yang, lead author of the Physical Review X paper that reported the group’s findings. The team captured the electrons by coaxing them to float above the surface of liquid helium at extremely low temperatures.

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Princeton’s answer to Quantum friction.

Abstract: Theoretical chemists at Princeton University have pioneered a strategy for modeling quantum friction, or how a particle’s environment drags on it, a vexing problem in quantum mechanics since the birth of the field. The study was published in the Journal of Physical Chemistry Letters.

“It was truly a most challenging research project in terms of technical details and the need to draw upon new ideas,” said Denys Bondar, a research scholar in the Rabitz lab and corresponding author on the work.

Quantum friction may operate at the smallest scale, but its consequences can be observed in everyday life. For example, when fluorescent molecules are excited by light, it’s because of quantum friction that the atoms are returned to rest, releasing photons that we see as fluorescence. Realistically modeling this phenomenon has stumped scientists for almost a century and recently has gained even more attention due to its relevance to quantum computing.

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(Phys.org)—A team of researchers with members from several institutions in the U.S. and one in Germany has proposed the idea of using an extremely small compass needle to build an ultrasensitive magnetometer. In their paper published in Physical Review Letters, the team describes their idea and the possibility of such a device actually being built.

Current magnetometers are very sensitive, able to detect levels of magnetism that are approximately a trillion times less than that of the Earth’s magnetic field. They achieve this feat by taking advantage of the wobble that occurs when an atom is placed in a magnetic field—such magnetometers are made by placing cells of atomic gas in a magnetic field, the wobbles of the are averaged to arrive at a single measurement. In this new effort, the researchers suggest that a new way to measure magnetic fields could be perhaps as much as 1000 times more sensitive.

The idea behind the still theoretically magnetometer comes from the way a compass needle works—instead of wobbling when exposed to a magnetic field, it simply lines up—at least when viewed from a distance. The researchers have shown that such needles do actually wobble like atoms, when they are very small and placed in a very weak magnetic field. They envision a very tiny needle made of cobalt with all of its atoms aligned in a single direction. When the needed is placed in a weak magnetic field, the angular momentum of the rotation of the needle would be a lot smaller than its intrinsic , which means it would precess, very much like single atoms do. Measuring the precess then would offer a means of measuring the level of magnetism.

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A tool able to generate remote forces would allow us to handle dangerous or fragile materials without contact or occlusions. Acoustic levitation is a suitable technology since it can trap particles in air or water. However, no approach has tried to endow humans with an intertwined way of controlling it. Previously, the acoustic elements were static, had to surround the particles and only translation was possible. Here, we present the basic manoeuvres that can be performed when levitators are attached to our moving hands. A Gauntlet of Levitation and a Sonic Screwdriver are presented with their manoeuvres for capturing, moving, transferring and combining particles. Manoeuvres can be performed manually or assisted by a computer for repeating patterns, stabilization and enhanced accuracy or speed. The presented prototypes still have limited forces but symbolize a milestone in our expectations of future technology.

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Theoretical chemists at Princeton University have pioneered a strategy for modeling quantum friction, or how a particle’s environment drags on it, a vexing problem in quantum mechanics since the birth of the field. The study was published in the Journal of Physical Chemistry Letters (“Wigner–Lindblad Equations for Quantum Friction”). “It was truly a most challenging research project in terms of technical details and the need to draw upon new ideas,” said Denys Bondar, a research scholar in the Rabitz lab and corresponding author on the work.

Researchers construct a quantum counterpart of classical friction, a velocity-dependent force acting against the direction of motion

Researchers construct a quantum counterpart of classical friction, a velocity-dependent force acting against the direction of motion. In particular, a translationary invariant Lindblad equation is derived satisfying the appropriate dynamical relations for the coordinate and momentum (i.e., the Ehrenfest equations). Numerical simulations establish that the model approximately equilibrates. (© ACS)

Quantum friction may operate at the smallest scale, but its consequences can be observed in everyday life. For example, when fluorescent molecules are excited by light, it’s because of quantum friction that the atoms are returned to rest, releasing photons that we see as fluorescence. Realistically modeling this phenomenon has stumped scientists for almost a century and recently has gained even more attention due to its relevance to quantum computing.

Read more