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Category: quantum physics – Page 818

Dynamic DNA material with emergent locomotion behavior powered by artificial metabolism

Interesting research paper on a new nanobot technology. I’m watching for ways in which suitable substrates for mind uploading can be constructed, and DNA self-guided assembly has potential.

Here are some excerpts and a weblink to the paper:

“…Chemical approaches have opened synthetic routes to build dynamic materials from scratch using chemical reactions, ultimately allowing flexibility in design…”

… As a realization of this concept, we engineered a mechanism termed DASH—DNA-based Assembly and Synthesis of Hierarchical materials—providing a mesoscale approach to create dynamic materials from biomolecular building blocks using artificial metabolism. DASH was developed on the basis of nanotechnology that uses DNA as a generic material ranging from nanostructures to hydrogels, for enzymatic substrates, and as linkers between nanoparticles…”

“…Next, to illustrate the potential uses of self-generated materials, we created various hybrid functional materials from the DASH patterns. The DASH patterns served as a versatile mesoscale scaffold for a diverse range of functional nanomaterials beyond DNA, ranging from proteins to inorganic nanoparticles, such as avidin, quantum dots, and DNA-conjugated gold nanoparticles (AuNPs) (Fig. 4D, figs. S37 and S38, and Supplementary Text). The generated patterns were also rendered functional with catalytic activity when conjugated with enzymes (figs. S39 and S40 and Supplementary Text). We also showed that the DNA molecules within the DASH patterns retained the DNA’s genetic properties and that, in a cell-free fashion, the materials themselves successfully produced green fluorescent proteins (GFPs) by incorporating a reporter gene for sfGFP (Fig. 4E and figs. S9 and S41) (40). The protein production capability of the materials established the foundation for future cell-free production of proteins, including enzymes, in a spatiotemporally controlled manner.

…” Our implementation of the concept, DASH, successfully demonstrated various applications of the material. We succeeded in constructing machines from this novel dynamic biomaterial with emergent regeneration, locomotion, and racing behaviors by programming them as a series of FSAs. Bottom-up design based on bioengineering foundations without restrictions of life fundamentally allowed these active and programmable behaviors. It is not difficult to envision that the material could be integrated as a locomotive ele-ment in biomolecular machines and robots. The DASH patterns could be easily recognized by naked eyes or smartphones, which may lead to better detection technologies that are more feasible in point-of-care settings. DASH may also be used as a template for other materials, for example, to create dynamic waves of protein expression or nanoparticle assemblies. In addition, we envision that further expansion of artificial metabolism may be used for self-sustaining structural components and self-adapting substrates for chemical production pathways. Ultimately, our material may allow the construction of self-reproducing machines through the production of enzymes from generated materials that, in turn, reproduce the material. Our biomaterial powered by artificial metabolism is an important step toward the creation of “artificial” biological systems with dynamic, life-like capabilities.”…

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Satellite test shows objects in space fall at a rate to within two-trillionths of a percent of each other

A team of researchers affiliated with several institutions in France and one in the U.S. has found that objects of different mass dropped in space fall at a rate within two-trillionths of a percent of each other. In their paper published in the journal Physical Review Letters, the group describes their satellite-based physics study and what they learned from it.

Most everyone has heard the story of Galileo dropping two different sized cannon balls from the Tower of Pisa in the 17th century to demonstrate his theory that in the absence of air resistance, two objects will fall at the same rate. Einstein later refined the theory and added it to his Theory of General Relativity. Since that time, many people have tested the theory, and it has always been confirmed. Still, some physicists believe that there are bound to be exceptions to the because of the disconnect between general relativity and quantum mechanics. In this new effort, the team in France devised an experiment to measure two objects dropping together for two years—specifically, two chunks of metal in a satellite—to see if they could spot an exception.

The two chunks of a platinum-rhodium alloy and a mass of titanium-aluminum-vanadium alloy were installed in a device the team called the Twin-Space Accelerometer for Gravity Experiment (T-SAGE), which was on board a satellite with the acronym MICROSCOPE. The was launched into space aboard a Soyuz rocket from the Guiana Space Centre ELS.

IBM Doubles Its Quantum Volume to 32

IBM announced a new 28-qubit quantum system backend, Raleigh and achieved a system demonstrating Quantum Volume of 32. This is double the quantum volume of 16 of a prior IBM system.

Quantum Volume (QV) is a hardware-agnostic metric that we defined to measure the performance of a real quantum computer. Each system IBM develop brings us along a path where complex problems will be more efficiently addressed by quantum computing; therefore, the need for system benchmarks is crucial, and simply counting qubits is not enough. Quantum Volume takes into account the number of qubits, connectivity, and gate and measurement errors. Material improvements to underlying physical hardware, such as increases in coherence times, reduction of device crosstalk, and software circuit compiler efficiency, can point to measurable progress in Quantum Volume, as long as all improvements happen at a similar pace.

Synopsis: Levitated Nanoparticle Goes Quantum

Optically levitated nanosphere shows definitive signature of its quantum ground state of motion.

Picture a marble rolling around inside a bowl. The motion of the marble represents its center-of-mass temperature, a quantity distinct from the object’s physical temperature. Now replace the marble with a levitated nanosphere and the bowl with an optical trap, and you have the experiment used by Felix Tebbenjohanns and colleagues at the Swiss Federal Institute of Technology (ETH), Zurich, to reduce a levitated nanoparticle’s center-of-mass temperature to close to its quantum ground state. The experimental signature showing that the nanosphere had entered the quantum regime had, until now, been seen only in mechanically clamped systems coupled to optical cavities.

False Alarm: The So-Called ‘Angel Particle’ Is Still a Mystery

A 2017 report of the discovery of a particular kind of Majorana fermion — the chiral Majorana fermion, referred to as the “angel particle” — is likely a false alarm, according to new research. Majorana fermions are enigmatic particles that act as their own antiparticle and were first hypothesized to exist in 1937. They are of immense interest to physicists because their unique properties could allow them to be used in the construction of a topological quantum computer.

A team of physicists at Penn State and the University of Wurzburg in Germany led by Cui-Zu Chang, an assistant professor of physics at Penn State studied over three dozen devices similar to the one used to produce the angel particle in the 2017 report. They found that the feature that was claimed to be the manifestation of the angel particle was unlikely to be induced by the existence of the angel particle. A paper describing the research appears on January 3, 2020 in the journal Science.

“When the Italian physicist Ettore Majorana predicted the possibility of a new fundamental particle which is its own antiparticle, little could he have envisioned the long-lasting implications of his imaginative idea.”

Scientists Find Evidence a Strange Group of Quantum Particles Are Basically Immortal

Nothing lasts forever. Humans, planets, stars, galaxies, maybe even the Universe itself, everything has an expiration date. But things in the quantum realm don’t always follow the rules. Scientists have found that quasiparticles in quantum systems could be effectively immortal.

That doesn’t mean they don’t decay, which is reassuring. But once these quasiparticles have decayed, they are able to reorganise themselves back into existence, possibly ad infinitum.

This seemingly flies right in the face of the second law of thermodynamics, which asserts that entropy in an isolated system can only move in an increasing direction: things can only break down, not build back up again.

Clusters of gold atoms form peculiar pyramidal shape

Clusters composed of a few atoms tend to be spherical. They are usually organized in shells of atoms around a central atom. This is the case for many elements, but not for gold! Experiments and advanced computations have shown that freestanding clusters of twenty gold atoms take on a pyramidal shape. They have a triangular ground plane made up of ten neatly arranged atoms, with additional triangles of six and three atoms, topped by a single atom.

The remarkable tetrahedral structure has now been imaged for the first time with a scanning tunnelling microscope. This high-tech microscope can visualise single atoms. It operates at extremely low temperatures (269 degrees below zero) and uses quantum tunnelling of an electrical current from a sharp scanning metallic tip through the cluster and into the support. Quantum tunnelling is a process where electrical current flows between two conductors without any physical contact between them.

The researchers used intense plasmas in a complex vacuum chamber setup to sputter gold atoms from a macroscopic piece of gold. “Part of the sputtered atoms grow together to small particles of a few up to a few tens of atoms, due to a process comparable with condensation of water molecules to droplets,” says Zhe Li, the main author of the paper, currently at the Harbin Institute of Technology, Shenzhen. “We selected a beam of clusters consisting of exactly twenty gold atoms. We landed these species with one of the triangular facets onto a substrate covered with a very thin layer of kitchen salt (NaCl), precisely three atom layers thick.”

The study also revealed the peculiar electronic structure of the small gold pyramid. Similar to noble gas atoms or aromatic molecules, the cluster only has completely filled electron orbitals, which makes them much less reactive than clusters with one or a few atoms more or less.

Gold clusters ranging from a few to several dozens of atoms in size are known to possess remarkable properties.

Freestanding clusters of twenty gold atoms take the shape of a pyramid, researchers discovered. This is in contrast with most elements, which organize themselves by forming shells around one central atom.

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