Interactions with cosmic rays could make low-mass dark matter particles detectable by neutrino observatories. But an analysis of two decades’ worth of data shows no signs of the particles.
As buzz grows ever louder over the future of quantum, researchers everywhere are working overtime to discover how best to unlock the promise of super-positioned, entangled, tunneling or otherwise ready-for-primetime quantum particles, the ability of which to occur in two states at once could vastly expand power and efficiency in many applications.
Developmentally, however, quantum devices today are “about where the computer was in the 1950s,” which it is to say, the very beginning. That’s according to Kamyar Parto, a sixth-year Ph.D. student in the UC Santa Barbara lab of Galan Moody, an expert in quantum photonics and an assistant professor of electrical and computer engineering.
Parto is co-lead author of a paper published in the journal Nano Letters, describing a key advance: the development of a kind of on-chip “factory” for producing a steady, fast stream of single photons, essential to enabling photonic-based quantum technologies.
Plasma is matter that is so hot that the electrons are separated from atoms. The electrons float freely and the atoms become ions. This creates an ionized gas—plasma—that makes up nearly all of the visible universe. Recent research shows that magnetic fields can spontaneously emerge in a plasma. This can happen if the plasma has a temperature anisotropy—temperature that is different along different spatial directions.
This mechanism is known as the Weibel instability. It was predicted by plasma theorist Eric Weibel more than six decades ago but only now has been unambiguously observed in the laboratory. New research, now published in Proceedings of the National Academy of Sciences, finds that this process can convert a significant fraction of the energy stored in the temperature anisotropy into magnetic field energy. It also finds that the Weibel instability could be a source of magnetic fields that permeate throughout the cosmos.
The matter in our observable universe is plasma state and it is magnetized. Magnetic fields at the micro-gauss level (about a millionth of the Earth’s magnetic fields) permeate the galaxies. These magnetic fields are thought to be amplified from weak seed fields by the spiral motion of the galaxies, known as the galactic dynamo. How the seed magnetic fields are created is a longstanding question in astrophysics.
Bosons, one of the two fundamental classes of particles, have been the focus of countless physics studies. When bosonic particles are transitioning into an already occupied final quantum state, the rate of this transition is enhanced by its so-called “occupation number,” an effect known as bosonic stimulation. The appearance of bosonic stimulation in light scattering processes was first predicted over three decades ago, yet directly observing it in experimental settings has so far proved challenging.
Researchers at the MIT-Harvard Center for Ultracold Atoms have recently observed bosonic enhanced light scattering in an ultracold gas for the first time. Their findings, published in Nature Physics, could open new exciting possibilities for the study of bosonic systems.
“For bosons, the transition rate into an already occupied quantum state is enhanced by its occupation number: the effect of bosonic stimulation,” Yu-Kun Lu, one of the researchers who carried out the study, told Phys.org.
Powered by supermassive black holes swallowing matter in the centers of galaxies, active galactic nuclei are the most powerful compact steady sources of energy in the universe. The brightest active galactic nuclei have long been known to far outshine the combined light of the billions of stars in their host galaxies.
A new study indicates that scientists have substantially underestimated the energy output of these objects by not recognizing the extent to which their light is dimmed by dust.
“When there are intervening small particles along our line of sight, this makes things behind them look dimmer. We see this at sunset on any clear day when the sun looks fainter,” said Martin Gaskell, a research associate in astronomy and astrophysics at UC Santa Cruz.
Just over a decade ago, physicist and Nobel laureate Frank Wilczek from MIT wrote a paper musing about the potential properties of a theoretical object he called quantum time crystal. To the surprise of many, over the last few years, those time crystals have been found aplenty both in specific lab experiments and inside common things like children’s toys.
As is often the case, the exact nature of these objects is not widely understood. So let’s tackle this question together: what is a time crystal? First and foremost, let’s define what a crystal is. Let’s consider empty space like a blank sheet of paper extending as far as the eye can see. There is no special point to it because every point is the same.
That’s where the translational symmetry comes in. No point is special – but now let’s imagine that the paper is graphed, like sheets you might have used in math lessons. Now you will have a lot of empty space, but every little while you have lines and corners, etc. That is a repeating regular structure. In your regular crystal, from diamonds to snowflakes, their atoms are organized in repeating patterns like that.
A quantum harmonic oscillator—a structure that can control the location and energy of quantum particles that could, in the future, be used to develop new technologies including OLEDs and miniature lasers—has been made at room temperature by researchers led by the University of St Andrews.
The research, conducted in collaboration with scientists at Nanyang Technological University in Singapore and published in Nature Communications recently, used an organic semiconductor to produce polaritons, which show quantum states even at room temperature.
Polaritons are quantum mixtures of light and matter that are made by combining excitations in a semiconductor material with photons, the fundamental particles that form light. To create polaritons, the researchers trapped light in a thin layer of an organic semiconductor (the kind of light-emitting material used in OLED smartphone displays) 100 times thinner than a single human hair, sandwiched between two highly reflective mirrors.
The meteorite and explosion-site quasicrystals were both uncovered by a team that includes Luca Bindi of the University of Florence, Italy, and Paul Steinhardt of Princeton University. In those previous cases, the materials were subjected to extremely high-pressure, high-temperature shock events—analysis of the meteorite sample revealed the temperature reached at least 1,200 °C and the pressure 5 GPa, while the New Mexico sample reached 1,500 °C and closer to 8 GPa. These transient, intense conditions contorted the materials’ atoms, forcing them to arrange into patterns unseen for usual laboratory conditions.
The explosion-site sample was found in a rock-like substance made of sand that had been fused together with copper wires from a measurement device that had been set up to monitor the atom-bomb test. As a trained geologist, Bindi was aware that similar substances—so-called fulgurites—are created when lightning strikes a beach or a sand dune. He wondered if lightning-fused samples might also contain quasicrystals, so he and the team set about collecting and analyzing the structures of as many fulgurites as they could lay their hands on.
Luck was on their side. In a fragment of a storm-created fulgurite from the Nebraskan Sand Hills—grass-stabilized sand dunes in northern Nebraska—the team found a micron-sized fragment of a quasicrystal with a previously unseen composition and pattern. Specifically, the newly discovered quasicrystal has a dodecagonal—12-fold symmetric—atomic structure. Such ordering is impossible in ordinary crystals, Bindi says, and is unusual even for quasicrystals (both the meteorite and explosion-site quasicrystals, as well as most lab-made ones, have fivefold symmetric patterns). “This was all more than [we] could have hoped for in such a long-shot search,” Steinhardt says.
Japan says it will release more than a million tonnes of water into the sea from the destroyed Fukushima nuclear power plant this year.
After treatment the levels of most radioactive particles meet the national standard, the operator said.
The International Atomic Energy Agency (IAEA) says the proposal is safe, but neighbouring countries have voiced concern.
Researchers have developed a way to use laser light to pull a macroscopic object. Although microscopic optical tractor beams have been demonstrated before, this is one of the first times that laser pulling has been used on larger objects.
Light contains both energy and momentum that can be used for various types of optical manipulation such as levitation and rotation. Optical tweezers, for example, are commonly used scientific instruments that use laser light to hold and manipulate tiny objects such as atoms or cells. For the last ten years, scientists have been working on a new type of optical manipulation: using laser light to create an optical tractor beam that could pull objects.
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