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(Phys.org)—Ever since the early days of quantum mechanics, the decay dynamics of unstable quantum systems has been thought to follow an exponential decay law, just like the one used to describe radioactive decay and many other natural processes. The exponential law in the quantum domain was originally proposed by George Gamow and later developed by Eugene Wigner and Victor Weisskopf. According to this law, when given a sample of unstable atoms, the number of those that are likely to decay during a brief period of time is proportional to the number of atoms present.

In the years since then, however, physicists have found that deviations from the exponential law can occur in unstable quantum systems, but only in those that are isolated from the external environment. This is because isolated systems are free from environmental decoherence, which makes it possible for the quantum decay products to reconstruct themselves back into their initial, pre-decayed states. Consequently, the decay is initially slower than that predicted by the exponential law, and in the later stages, the decay often exhibits a power-law behavior. Researchers have previously shown that this nonexponential decay can be harnessed for quantum control.

Now in a new study, physicists have theoretically shown that quantum decay processes can deviate from the exponential decay law not only when the system is isolated, but even when it is in contact with the external environment. The results suggest that an unstable quantum system can decay and subsequently return to its original state, even in the presence of environmental decoherence.

Aleksandr Noy has big plans for a very small tool. A senior research scientist at Lawrence Livermore National Laboratory, Noy has devoted a significant part of his career to perfecting the liquid alchemy known as desalination—removing salt from seawater. His stock-in-trade is the carbon nanotube. In 2006, Noy had the audacity to embrace a radical theory: Maybe nanotubes—cylinders so tiny, they can be seen only with an electron microscope—could act as desalination filters. It depended on just how wide the tubes were. The opening needed to be big enough to let water molecules flow through but small enough to block the larger salt particles that make seawater undrinkable. Put enough carbon nanotubes together and you potentially have the world’s most efficient machine for making clean water.

In a classical thermodynamic system, heat current flows from the hotter body to the colder one, or electricity from the higher voltage to the lower one. The same thing happens in quantum systems, but this state can be changed, and the flow of energy and particles can be reversed if a quantum observer is inserted into the system.

This is the main result obtained by the group led by Professor Ángel Rubio of the UPV/EHU and of the Max Planck Institute PMSD, together with collaborators at the BCCMS centre in Bremen. Their study has been published in npj Quantum Materials.

In macroscopic objects such as a current of water, observing the current does not affect the flow of the water and, in accordance with the laws of classical thermodynamics, this flow would take place from the upper to the lower part of the system. However, in quantum systems, “the process of observation changes the state of the system, and this makes it more likely that the current will be made to flow in one direction or another,” says Ángel Rubio, a professor with the Hamburg-based Max Planck Institute for the Structure and Dynamics of Matter.

A thruster that’s being developed for a future NASA mission to Mars broke several records during recent tests, suggesting that the technology is on track to take humans to the Red Planet within the next 20 years, project team members said.

The X3 thruster, which was designed by researchers at the University of Michigan in cooperation with NASA and the U.S. Air Force, is a Hall thruster — a system that propels spacecraft by accelerating a stream of electrically charged atoms, known as ions. In the recent demonstration conducted at NASA’s Glenn Research Center in Ohio, the X3 broke records for the maximum power output, thrust and operating current achieved by a Hall thruster to date, according to the research team at the University of Michigan and representatives from NASA.

“We have shown that X3 can operate at over 100 kW of power,” said Alec Gallimore, who is leading the project, in an interview with Space.com. “It operated at a huge range of power from 5 kW to 102 kW, with electrical current of up to 260 amperes. It generated 5.4 Newtons of thrust, which is the highest level of thrust achieved by any plasma thruster to date,” added Gallimore, who is dean of engineering at the University of Michigan. The previous record was 3.3 Newtons, according to the school.

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Scientists at The University of Manchester have created the world’s first ‘molecular robot’ that is capable of performing basic tasks including building other molecules.

The tiny robots, which are a millionth of a millimetre in size, can be programmed to move and build molecular cargo, using a tiny robotic arm.

Each individual robot is capable of manipulating a single molecule and is made up of just 150 carbon, hydrogen, oxygen and nitrogen atoms. To put that size into context, a pile of a billion billion of these robots would still only be the same size (volume/weight) as a few grains of salt.

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Do you remember all the hoopla last year when the Higgs Boson was confirmed by physicists at the Large Hadron Collider? That’s the one called the ‘God particle’, because it was touted as helping to resolve the forces of nature into one elegant theory. Well—Not so fast, bucko!…

First, some credit where credit is due: The LHC is a 27-kilometer ring of superconducting magnets interspersed by accelerators that boost the energy of the particles as they whip around and smash into each other. For physicists—and anyone who seeks a deeper understanding of what goes into everything—it certainly inspires awe.

Existence of the Higgs Boson (aka, The God Particle) was predicted. Physicists were fairly certain that it would be observed. But its discovery is a ‘worst case’ scenario for the Standard Model of particle physics. It points to shortcomings in our ability to model and predict things. Chemists have long had a master blueprint of atoms in the Periodic Table. It charts all the elements in their basic states. But, physicists are a long way from building something analogous. That’s because we know a lot more about atomic elements than the fundamental building blocks of matter and energy. _{[continue below image]}

Continue reading “Fundamental Particles & Forces: What do we know?” »

Pioneered by Erik Verlinde, the idea is that gravity emerges from a more fundamental phenomenon in the Universe, and that phenomenon is entropy.

“Sound waves emerge from molecular interactions; atoms emerge from quarks, gluons and electrons and the strong and electromagnetic interactions; planetary systems emerge from gravitation in General Relativity. But in the idea of entropic gravity — as well as some other scenarios (like qbits) — gravitation or even space and time themselves might emerge from other entities in a similar fashion. There are well-known, close relationships between the equations that govern thermodynamics and the ones that govern gravitation. It’s known that the laws of thermodynamics emerge from the more fundamental field of statistical mechanics, but is there something out there more fundamental from which gravity emerges? That’s the idea of entropic gravity.”

Continue reading “Are Space, Time, And Gravity All Just Illusions?” »

Every 100 years or so, our Sun gives off a great big belch that sends an intense wave of charged particles towards Earth. This wasn’t a problem in the past, but our high-tech civilization is now disturbingly vulnerable to these solar storms. A new study quantifies the economic risks posed by these extreme solar storms, while also proposing a super-futuristic solution to the problem: an Earth-sized shield built in outer space.

The term “solar storm” is used to identify the various nasties the Sun can hurl our way, including x-rays, charged particles, and magnetized plasma. In 1859, a series of powerful coronal mass ejections (CMEs) hit our planet head on, disrupting telegraph stations and causing widespread communication outages. If we were to be hit by an equally powerful solar storm today, it would knock out satellites and electrical grids, disrupting global communications, transportation, and supply chains. Total worldwide losses could reach up to $10 trillion, with recovery taking many years.

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