In the quantum realm, not even time flows as you might expect

Artistic illustration of a gondolier trapped in a
quantum superposition of time flows.
Credit: Aloop Visual and Science, University of Vienna

A team of physicists at the Universities of Bristol, Vienna, the Balearic Islands and the Institute for Quantum Optics and Quantum Information (IQOQI-Vienna) has shown how quantum systems can simultaneously evolve along two opposite time arrows - both forward and backward in time.

The study, published in the latest issue of Communications Physics, necessitates a rethink of how the flow of time is understood and represented in contexts where quantum laws play a crucial role.

For centuries, philosophers and physicists have been pondering the existence of time. Yet, in the classical world, our experience seems to extinguish any doubt that time exists and goes on. Indeed, in nature, processes tend to evolve spontaneously from states with less disorder to states with more disorder and this propensity can be used to identify an arrow of time. In physics, this is described in terms of ‘entropy’, which is the physical quantity defining the amount of disorder in a system.

Dr Giulia Rubino from the University of Bristol’s Quantum Engineering Technology Labs (QET labs) and lead-author of the publication, said: “If a phenomenon produces a large amount of entropy, observing its time-reversal is so improbable as to become essentially impossible. However, when the entropy produced is small enough, there is a non-negligible probability of seeing the time-reversal of a phenomenon occur naturally.

“We can take the sequence of things we do in our morning routine as an example. If we were shown our toothpaste moving from the toothbrush back into its tube, we would be in no doubt it was a rewinded recording of our day. However, if we squeezed the tube gently so only a small part of the toothpaste came out, it would not be so unlikely to observe it re-entering the tube, sucked in by the tube’s decompression.”

The authors of the study, under the lead of Professor Caslav Brukner of the University of Vienna and the IQOQI-Vienna, applied this idea to the quantum realm, one of whose peculiarities is the principle of quantum superposition, according to which if two states of a quantum system are both possible, then that system can also be in both states at the same time.

Dr Rubino said: “Extending this principle to time’s arrows, it results that quantum systems evolving in one or the other temporal direction (the toothpaste coming out of or going back into the tube), can also find themselves evolving simultaneously along both temporal directions.

“Although this idea seems rather nonsensical when applied to our day-to-day experience, at its most fundamental level, the laws of the universe are based on quantum-mechanical principles. This begs the question of why we never encounter these superpositions of time flows in nature."

Dr Gonzalo Manzano, co-author from the University of the Balearic Islands, said: “In our work, we quantified the entropy produced by a system evolving in quantum superposition of processes with opposite time arrows. We found this most often results in projecting the system onto a well-defined time’s direction, corresponding to the most likely process of the two. And yet, when small amounts of entropy are involved (for instance, when there is so little toothpaste spilled that one could see it being reabsorbed into the tube), then one can physically observe the consequences of the system having evolved along the forward and backward temporal directions at the same time.”

Aside from the fundamental feature that time itself might not be well-defined, the work also has practical implications in quantum thermodynamics. Placing a quantum system in a superposition of alternative time’s arrows could offer advantages in the performance of thermal machines and refrigerators.

Dr Rubino said: “Although time is often treated as a continuously increasing parameter, our study shows the laws governing its flow in quantum mechanical contexts are much more complex. This may suggest that we need to rethink the way we represent this quantity in all those contexts where quantum laws play a crucial role.”

Source/Credit: University of Bristol

phy112621_01

Extraordinary Roman mosaic and villa discovered beneath farmer's field in Rutland

Archaeologists have unearthed the first Roman mosaic of its kind in the UK. Today (Thursday), a rare Roman mosaic and surrounding villa complex have been protected as a Scheduled Monument by DCMS on the advice of Historic England. The decision follows archaeological work undertaken by a team from University of Leicester Archaeological Services (ULAS), working in partnership with Historic England and in liaison with Rutland County Council.

The initial discovery of the mosaic was made during the 2020 lockdown by Jim Irvine, son of landowner Brian Naylor, who contacted the archaeological team at Leicestershire County Council, heritage advisors to the local authority. Given the exceptional nature of this discovery, Historic England was able to secure funding for urgent archaeological investigations of the site by ULAS in August 2020. Further excavation involving staff and students from the University of Leicester’s School of Archaeology and Ancient History examined more of the site in September 2021. The remains of the mosaic measure 11m by almost 7m and depict part of the story of the Greek hero Achilles.

The artwork forms the floor of what’s thought to be a large dining or entertaining area. Mosaics were used in a variety of private and public buildings across the Roman Empire, and often featured famous figures from history and mythology. However, the Rutland mosaic is unique in the UK in that it features Achilles and his battle with Hector at the conclusion of the Trojan War and is one of only a handful of examples from across Europe.

Super jelly’ can survive being run over by a car

The soft-yet-strong material, developed by a team at the University of Cambridge, looks and feels like a squishy jelly, but acts like an ultra-hard, shatterproof glass when compressed, despite its high water content.

The non-water portion of the material is a network of polymers held together by reversible on/off interactions that control the material’s mechanical properties. This is the first time that such significant resistance to compression has been incorporated into a soft material.

The ‘super jelly’ could be used for a wide range of potential applications, including soft robotics, bioelectronics or even as a cartilage replacement for biomedical use. The results are reported in the journal Nature Materials.

The way materials behave – whether they’re soft or firm, brittle or strong – is dependent upon their molecular structure. Stretchy, rubber-like hydrogels have lots of interesting properties that make them a popular subject of research – such as their toughness and self-healing capabilities – but making hydrogels that can withstand being compressed without getting crushed is a challenge.

“In order to make materials with the mechanical properties we want, we use crosslinkers, where two molecules are joined through a chemical bond,” said Dr Zehuan Huang from the Yusuf Hamied Department of Chemistry, the study’s first author. “We use reversible crosslinkers to make soft and stretchy hydrogels, but making a hard and compressible hydrogel is difficult and designing a material with these properties is completely counterintuitive.”

Working in the lab of Professor Oren A. Scherman, who led the research, the team used barrel-shaped molecules called cucurbiturils to make a hydrogel that can withstand compression. The cucurbituril is the crosslinking molecule that holds two guest molecules in its cavity – like a molecular handcuff. The researchers designed guest molecules that prefer to stay inside the cavity for longer than normal, which keeps the polymer network tightly linked, allowing for it to withstand compression.

Super jelly  Credit: Zehuan Huang

“At 80% water content, you’d think it would burst apart like a water balloon, but it doesn’t: it stays intact and withstands huge compressive forces,” said Scherman, Director of the University’s Melville Laboratory for Polymer Synthesis. “The properties of the hydrogel are seemingly at o
dds with each other.”

“The way the hydrogel can withstand compression was surprising, it wasn’t like anything we’ve seen in hydrogels,” said co-author Dr Jade McCune, also from the Department of Chemistry. “We also found that the compressive strength could be easily controlled through simply changing the chemical structure of the guest molecule inside the handcuff.”

To make their glass-like hydrogels, the team chose specific guest molecules for the handcuff. Altering the molecular structure of guest molecules within the handcuff allowed the dynamics of the material to ‘slow down’ considerably, with the mechanical performance of the final hydrogel ranging from rubber-like to glass-like states.

“People have spent years making rubber-like hydrogels, but that’s just half of the picture,” said Scherman. “We’ve revisited traditional polymer physics and created a new class of materials that span the whole range of material properties from rubber-like to glass-like, completing the full picture.”

The researchers used the material to make a hydrogel pressure sensor for real-time monitoring of human motions, including standing, walking and jumping.

“To the best of our knowledge, this is the first time that glass-like hydrogels have been made. We’re not just writing something new into the textbooks, which is really exciting, but we’re opening a new chapter in the area of high-performance soft materials,” said Huang.

Researchers from the Scherman lab are currently working to further develop these glass-like materials towards biomedical and bioelectronic applications in collaboration with experts from engineering and materials science. The research was funded in part by the Leverhulme Trust and a Marie Skłodowska-Curie Fellowship. Oren Scherman is a Fellow of Jesus College.

Source/Credit: University of Cambridge

tn112521_01

Electrons Set the Stage for Neutrino Experiments

Neutrinos may be the key to finally solving a mystery of the origins of our matter-dominated universe, and preparations for two major, billion-dollar experiments are underway to reveal the particles’ secrets. Now, a team of nuclear physicists have turned to the humble electron to provide insight for how these experiments can better prepare to capture critical information. Their research, which was carried out at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility and recently published in Nature, reveals that major updates to neutrino models are needed for the experiments to achieve high-precision results.

Neutrinos are ubiquitous, generated in copious numbers by stars throughout our universe. Though prevalent, these shy particles rarely interact with matter, making them very difficult to study.

“There is this phenomenon of neutrinos changing from one type to another, and this phenomenon is called neutrino oscillation. It’s interesting to study this phenomenon, because it is not well understood,” said Mariana Khachatryan, a co-lead author on the study who was a graduate student at Old Dominion University in Professor and Eminent Scholar Larry Weinstein’s research group when she contributed to the research. She is now a postdoctoral research associate at Florida International University.

One way to study neutrino oscillation is to build gigantic, ultra-sensitive detectors to measure neutrinos deep underground. The detectors typically contain dense materials with large nuclei, so neutrinos are more likely to interact with them. Such interactions trigger a cascade of other particles that are recorded by the detectors. Physicists can use that data to tease out information about the neutrinos.

Misinformation about COVID-19 spreads faster on social media

New research has found that the amount of misinformation related to COVID-19 is disproportionately higher than content produced by fact-checkers on Twitter. COVID misinformation also maintains attention and engagement for longer online than fact-based content.

The research, led by Open University academics, aimed to examine misinformation about COVID-19 online as a means of improving the effectiveness of the response to the pandemic.

Over 350,000 tweets that shared misinforming or fact-checking content related to COVID-19 between December 2019 to January 2021 were studied.

It was found that fact-checking may not be as successful as expected in reducing misinformation spread on Twitter. The amount of misinformation on COVID-19 was shared on Twitter around 3.5 times more than content trying to correct misinformation.

This highlighted the importance of fact-checkers making their content attractive and eye-catching to social media users – thereby more shareable and likely to gain traction on platforms.

Misinformation is also more often re-published or re-shared after some time than fact-checking. This is particularly observable in relation to conspiracy theories and COVID origins or causes as these are often much harder to debunk based on known facts (i.e. conspiracy theories are ‘beyond’ factual content and COVID causes still remain unclear).

Himalayan bats are functionally less diverse at high than at lower elevations, but show the same evolutionary diversity

Rohit Charkararty during fieldwork in the Himalayas
Credit: Emily Stanford

Million years of evolution have produced a dazzling variety of species, each uniquely adapted to its environment. A straightforward way to measuring biodiversity is by the number of species (taxonomic diversity). Recently, there is growing emphasis to quantify diversity also in other ways: a) functional diversity, which is the diversity of phenotypic traits that allow organisms to perform their ecological functions and b) phylogenetic diversity, meaning the variation in the branches in the tree of life. In a paper published recently in the journal “Scientific Reports” a team of scientists led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) compares these approaches: They found that species richness and functional diversity of Himalayan bat communities decline at high elevation without the loss of phylogenetic diversity. Their findings provide insights on the diversity of bats in the Himalayas and serve as an important baseline in assessing this diversity in the context of environmental changes.

Lead author Rohit Chakravarty from the Leibniz-IZW and his colleagues evaluated three different diversity approaches to identifying biodiversity patterns in bats in the Himalayas. Mountain regions provide ideal settings for these kinds of analyses as they encompass a high number of different climate and vegetation zones along elevational gradients over short spatial scales. “It is quite well known how species richness responds to these elevational gradients, but in order to understand the evolutionary processes that lead to this distribution of species, we need to analyze the diversity of traits and diversity in evolutionary history”, explains Chakravarty. The team caught bats at elevations between 1500 and 3500 meters in the western Himalayas and measured phenotypic traits related to their wing shape and echolocation calls – both important traits that determine foraging style. They compared this information with phylogenetic data of Himalayan bat species from the literature. “Phylogenetic diversity indicates the number of steps or evolutionary adaptations that differentiate species from each other”, says Chakravarty. “It is interesting from an evolutionary standpoint. Three species that sit on the same branch of the evolutionary tree have a shared history of evolution, that is, they evolved from a common ancestor and may hence show similar adaptations to environmental conditions.”

Collapse of ancient Liangzhu culture caused by climate change

Stalagmites in caves located southwest of the excavation site show
a climatic cause for the collapse of the ancient chinese Liangzhu culture.
Credit: Haiwei Zhang

"China's Venice of the Stone Age": The Liangzhu excavation site in eastern China is one of the most significant testimonies of Chinese civilization. More than 5000 years ago, the city had an elaborate water management system. Massive flooding triggered by anomalously intense monsoon rains caused a sudden collapse, as a team with geologist Christoph Spötl shows in Science Advances.

In the Yangtze Delta, about 160 kilometers southwest of Shanghai, the archeological ruins of Liangzhu City are located. There, a highly advanced culture blossomed about 5300 years ago, which is considered to be one of the earliest proofs of monumental water culture. The oldest evidence of large hydraulic engineering structures in China originates from this late Neolithic cultural site. 

The walled city had a complex system of navigable canals, dams and water reservoirs. This system made it possible to cultivate very large agricultural areas throughout the year. In the history of human civilization, this is one of the first examples of highly developed communities based on a water infrastructure. Metals, however, were still unknown in this culture. 

Thousands of elaborately crafted jade burial objects were found during excavations. Long undiscovered and underestimated in its historical significance, the archaeological site is now considered a well-preserved record of Chinese civilization dating back more than 5000 years. Liangzhu was declared a UNESCO World Heritage Site in 2019. However, the advanced civilization of this city, which was inhabited for almost 1000 years, came to an abrupt end. 

Secrets of planet formation take researchers on quest near and far

Students visit Bin Chen’s high pressure mineral
physics laboratory, learn from Robert Rapp.

From laboratory experiments to observations of young star systems, University of Hawaiʻi at Mānoa researchers are on a quest to understand how rocky planets like Earth form.

Planets form from disks of gas and dust that surround young stars. Previous research has shown that nearly all stars are born with such disks, and revealed hints of planet formation within them. Surveys for planets around other stars, termed “exoplanets,” have discovered that Earth-size and presumably rocky planets are common, and many stars have planets orbiting much closer to their host star than the Earth-Sun distance. But most of the steps between dust and planets are poorly understood, in part because they are obscured within the inner region of these proto-planetary disks.

The National Science Foundation (NSF) and NASA recently awarded a total of $1.3 million in three separate grants to teams of UH Mānoa scientists from the Department of Earth Sciences and Hawaiʻi Institute of Geophysics and Planetology in the School of Ocean and Earth Science and Technology (SOEST), the Institute for Astronomy (IfA), and the Information and Computer Science Department (ICS) to explore this inner realm around other stars—and our Sun—in search of the secrets to planet formation.

SOEST Earth Sciences professor Eric Gaidos, lead investigator on two of the grants, explained, “the story of planet formation is like an epic movie, where we could watch only the dramatic opening scene and the happy ending, but missed everything between, leaving us guessing about the main characters, their roles and most of the plot.”

Water disinfection byproduct disrupts reproductive hormones, damages pituitary in female mice

A byproduct formed during water disinfection disrupts hormones
that regulate reproduction in female mice, found Illinois
professor Lori Raetzman (left) and graduate student Rachel Gonzalez. 
Photo by L. Brian Stauffer

Chemical disinfection makes water from both natural sources and wastewater streams drinkable; however, the process also creates byproducts, not all of which are understood or regulated. A new study from University of Illinois Urbana-Champaign researchers has found that one byproduct disrupts hormones in the brain that regulate the female reproductive cycle in mice and also damages cells in the pituitary gland.

Iodoacetic acid, or IAA, is created when an oxidizing disinfectant such as chlorine reacts with the iodide naturally present in water, said study leader Lori Raetzman, a professor of molecular and integrative physiology. The new study’s findings of IAA’s effects on reproductive regulation in the brain complement previous work by study co-author Jodi Flaws, a professor of comparative biosciences, which found that IAA also disrupts function in and causes damage to ovary cells, indicating that the chemical could impact the entire reproductive system.

“We know we need to disinfect water, but the water that’s coming out of our taps isn’t pure – regulators only screen for the things they know about. Water regulatory bodies have not been looking for IAA,” Raetzman said. “This study is contributing to the growing body of evidence that suggests that IAA may impact reproduction, so it might be reasonable to have screening for this too, and to establish a safe level for it.”

Robust approach needed to reduce risk of disease transmission between humans and wild animals

Credit: Pixabay

The threat of disease transmission from conservationists moving wild animals between habitats or back into the wild needs to be urgently assessed to minimize risk. Experts at the University of Birmingham are calling on local and national health authorities and wildlife managers to adopt a robust approach.

In a new paper, published in Frontiers in Veterinary Science, researchers in the University’s College of Life and Environmental Sciences, collaborating with Wildlife Impact and other sector partners, have highlighted the issues using the example of translocated orangutans in Indonesia.

All three species of orangutans in Indonesia are listed as Critically Endangered, and moving animals between habitats is a fairly common practice as demands for agriculture, mining, and other natural resource use puts pressure on the forests they inhabit. Interactions and conflict between humans and orangutans sharing the same habitats also contributes to the complex problems facing these rare species across their range.

During the covid 19 pandemic, the team identified instances of orangutans being released who had been in direct contact or proximity to humans without any protective equipment. In some cases, formerly captive orangutans were released after long periods of contact and potential exposure to human diseases.

The team’s results suggest that there is a potential problem of pathogen transmission between humans and animals which needs to be properly understood and managed.