Significant new discovery in teleportation research -- Noise can improve the quality of quantum teleportation

In teleportation, the state of a quantum particle, or qubit, is transferred from one location to another without sending the particle itself. This transfer requires quantum resources, such as entanglement between an additional pair of qubits. In an ideal case, the transfer and teleportation of the qubit state can be done perfectly. However, real-world systems are vulnerable to noise and disturbances -- and this reduces and limits the quality of the teleportation.

Researchers from the University of Turku, Finland, and the University of Science and Technology of China, Hefei, have now proposed a theoretical idea and made corresponding experiments to overcome this problem. In other words, the new approach enables reaching high-quality teleportation despite the presence of noise.

"The work is based on an idea of distributing entanglement -- prior to running the teleportation protocol -- beyond the used qubits, i.e., exploiting the hybrid entanglement between different physical degrees of freedom," says Professor Jyrki Piilo from the University of Turku.

Conventionally, the polarisation of photons has been used for the entanglement of qubits in teleportation, while the current approach exploits the hybrid entanglement between the photons' polarisation and frequency.

"This allows for a significant change in how the noise influences the protocol, and as a matter of fact our discovery reverses the role of the noise from being harmful to being beneficial to teleportation," Piilo describes.

With conventional qubit entanglement in the presence of noise, the teleportation protocol does not work. In a case where there is initially hybrid entanglement and no noise, the teleportation does not work either.

"However, when we have hybrid entanglement and add noise, the teleportation and quantum state transfer occur in almost perfect manner," says Dr Olli Siltanen whose doctoral dissertation presented the theoretical part of the current research.

In general, the discovery enables almost ideal teleportation despite the presence of certain type of noise when using photons for teleportation.

"While we have done numerous experiments on different facets of quantum physics with photons in our laboratory, it was very thrilling and rewarding to see this very challenging teleportation experiment successfully completed," says Dr Zhao-Di Liu from the University of Science and Technology of China, Hefei.

"This is a significant proof-of-principle experiment in the context of one of the most important quantum protocols," says Professor Chuan-Feng Li from the University of Science and Technology of China, Hefei.

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What's quieter than a fish? A school of them

Swimming in schools makes fish surprisingly stealthy underwater, with a group able to sound like a single fish.

The new findings by Johns Hopkins University engineers working with a high-tech simulation of schooling mackerel, offers new insight into why fish swim in schools and promise for the design and operation of much quieter submarines and autonomous undersea vehicles.

"It's widely known that swimming in groups provides fish with added protection from predators, but we questioned whether it also contributes to reducing their noise," said senior author Rajat Mittal.

"Our results suggest that the substantial decrease in their acoustic signature when swimming in groups, compared to solo swimming, may indeed be another factor driving the formation of fish schools."

The work is newly published in Bioinspiration & Biomimetics.

The team created a 3D model based on the common mackerel to simulate different numbers of fish swimming, changing up their formations, how close they swam to one another, and the degrees to which their movements synched.

The model, which applies to many fish species, simulates one to nine mackerel being propelled forward by their tail fins.

The team found that a school of fish moving together in just the right way was stunningly effective at noise reduction: A school of seven fish sounded like a single fish.

"A predator, such as a shark, may perceive it as hearing a lone fish instead of a group," Mittal said.

"This could have significant implications for prey fish."

The single biggest key to sound reduction, the team found, was the synchronization of the school's tail flapping -- or actually the lack thereof.

If fish moved in unison, flapping their tail fins at the same time, the sound added up and there was no reduction in total sound.

But if they alternated tail flaps, the fish canceled out each other's sound, the researchers found.

"Sound is a wave," Mittal said. "Two waves can either add up if they are exactly in phase or they can cancel each other if they are exactly out of phase. That's kind of what's happening here though we're talking about faint sounds that would barely be audible to a human."

The tail fin movements that reduce sound also generate flow interaction between the fish that allow the fish to swim faster while using less energy, said lead author Ji Zhou, a Johns Hopkins graduate student studying mechanical engineering.

"We find that reduction in flow-generated noise does not have to come at the expense of performance," Zhou said.

"We found cases where significant reductions in noise are accompanied by noticeable increases in per capita thrust, due to the hydrodynamic interactions between the swimmers."

The team was surprised to find that the sound reduction benefits kick in as soon as one swimming fish joins another.

Noise reduction grows as more fish join a school, but the team expects the benefits to cap off at some point.

"Simply being together and swimming in any manner contributes to reducing the sound signature," Mittal said.

"No coordination between the fish is required."

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Wind farm noise exposure doesn't wake people up from their slumber more than road traffic noise

Short exposure to wind farm and road traffic noise triggers a small increase in people waking from their slumber that can fragment their sleep patterns, according to new Flinders University research.

But importantly, the new study also shows that wind farm noise isn't more disruptive to sleep than road traffic, which was a little more disruptive at the loudest audio level but not at more common levels.

Sleep researchers at Flinders University have studied the impact of exposure to wind farm noise during sleep in three new scientific publications to better understand its impact on Australians.

The study played 20-second wind farm and road traffic noise samples repeatedly during participants sleep using 3 different sound pressure levels to compare their sleep disruption responses between the two different noise types.

On a separate night, the study tested if longer 3-minute noise samples, including very low-frequency wind farm infrasound alone, resulted in sleep disturbance.

The researchers also found that wind farm infrasound at realistic levels was not audible to the human ear during wake and produced no evidence of sleep disruption. These findings were presented at the International conference on Wind Farm Noise in Dublin on June 22, 2023 and are still to be journal peer reviewed.

The project took 5 years to complete and involved over 460 sleep study nights from 68 participants who each spent seven consecutive nights in the sleep laboratory.

The participants were recruited from four groups, including people living near a wind farm with and without noise related sleep difficulties, a group of residents living near a busy suburban road and people living in quiet rural areas.

"In order to capture the most representative wind farm noise features and levels, we used noise samples from long-term measurements of wind farm noise. These were then reproduced in the sleep laboratory to replicate real-life noises in a much more controlled environment than is possible in field studies, where wind and noise conditions are highly variable. The study included direct sleep measurements using electroencephalography (EEG) as well as hearing tests and a range of daytime listening tests," says Dr. Bastient Lechat, one of several acoustics experts on the research team.

Professor Peter Catcheside, a sleep expert from Flinders University and the chief investigator, says that the findings show that both wind farm noise and road traffic noise disrupt sleep, depending mainly on noise loudness and sleep depth at the time of noise exposure.

"However, at realistic levels, these effects were quite small. We also found no evidence to suggest that wind farm noise is any more disruptive to sleep than road traffic noise. At the highest exposure level, road traffic noise was a little more sleep disruptive than wind farm noise."

Professor Catcheside says one of the study's aims was to determine if realistic levels of wind farm infrasound could be heard by study participants during wake or show any sign of EEG recorded brain activity changes when played during sleep.

"Our results align with previous studies and showed that infrasound played at realistic levels was not audible during wakefulness and produced no detectable EEG changes during sleep. Infrasound is therefore unlikely to explain noise complaints from wind farms, suggesting that other low frequency audible rumbling and thumping components deserve more attention towards better understanding wind farm noise effects on sleep."

Professor Catcheside says that while this study provides strong evidence that wind farm noise is not more disruptive to established sleep than road traffic noise, this does not rule out that people who are particularly noise sensitive or annoyed may find it more difficult to get to sleep when noise levels are noticeable.

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Can 'random noise' unlock our learning potential?

Though many of us may seek a quiet place in which to study, 'noise' may play a key role in helping some people improve their learning potential.

Edith Cowan University (ECU) has investigated the effects of transcranial random noise stimulation (tRNS) in a variety of settings and found the technology could have many applications.

Despite its name, tRNS doesn't utilize noise in the everyday, auditory sense of the word.

Rather, it sees electrodes attached to the head so a weak current can pass through specific parts of the brain.

Study lead Dr Onno van der Groen said the study showed tRNS has promise as a tool to assist people with compromised learning capabilities.

"The effect on learning is promising: it can speed up learning and help people with neurological conditions," Dr van der Groen said.

"So, people with learning difficulties you can use it to enhance learning rate, for example.

"It's also been trialled on people with visual deficits, such as after stroke and traumatic brain injury.

"When you add this type of stimulation during learning, you get better performance, faster learning and better attention afterwards as well."

Forming new pathways

Dr van der Groen said tRNS works by allowing the brain to form new connections and pathways, a process known as neuroplasticity.

"If you learn something, there has to be neuroplastic changes in your brain, which allows you to learn this information," he said.

"And this is a tool to enhance this neuroplasticity."

Dr van der Groen said tRNS had two effects on the brain: the 'acute' effect, which allows a person to perform better while undergoing tRNS, and the modulating effect which saw lasting results.

"If you do 10 sessions of a visual perception task with the tRNS and then come back and do it again without it, you'll find you perform better than the control group who hasn't used it," he said.

"Limitless" potential?

The idea of expanding one's learning potential via tech such as tRNS raises many questions.

While it's most pertinent to those with deficiencies and difficulties in learning, it also begs the question as to whether a neurotypical person can take their intelligence to new levels, similar to the concept in the movie 'Limitless'.

Dr van der Groen says the potential is there, but there are also signs it won't create a 'new level' of intelligence.

"The question is, if you're neurotypical, are you already performing at your peak," he said.

"There's a case study where they tried to enhance the mathematical skills of a super mathematician; with him, it didn't have much of an impact on his performance, presumably because he is already a top performer in that area.

"But it could be used if you're learning something new."

Where it's headed

Though the technology is still in its infancy and people are only able to access tRNS by entering controlled trials, Dr van der Groen said its practicality and apparent safety meant there was a lot of potential for a range of applications.

"The concept is relatively simple," he said.

"It's like a battery: the current runs from plus to minus, but it goes through your head as well.

"We're working on a study where we send the equipment to people, and they apply everything themselves remotely.

"So in that regards, it's quite easy to use."

Scientists worldwide are also investigating tRNS' effects on perception, working memory, sensory processing and other aspects of behaviour, with the technology showing promise as a treatment for a range of clinical conditions.

"We're still trying to find out how best we can use it," Dr van der Groen said.

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Preadolescents exposed to high levels of air pollution in their first years of life display changes in brain connectivity

Higher exposure to air pollution is associated with higher functional brain connectivity among several brain regions in preadolescents, while exposure to traffic noise was not, according to a study led by ISGlobal, an institution supported by "la Caixa" Foundation. The findings also identify the first years of life as the most sensitive period of exposure to air pollution.

Traffic-related air pollution and noise are affecting an increasing number of people worldwide. "We already know that children are particularly vulnerable to the effect of these exposures, because of their immature metabolism and developing brain," says ISGlobal researcher and senior author Mónica Guxens. In fact, several studies by Guxens and others have found an association between exposure to traffic-related air pollution during early childhood and alterations in the brain structure.

In this study, the research team used magnetic resonance imaging (MRI) to explore whether higher exposure to air pollution or noise could also be associated with possible alterations in brain connectivity (i.e. the way in which different brain regions interact). "The use of MRI has opened up new possibilities in epidemiological research for investigating the structure and the functioning of the brain," says Guxens.

The researchers used data of 2,197 children from the Generation R Study, born between April 2002 and Jan 2006 and living in Rotterdam, the Netherlands. Using land use models, they estimated levels of nitrogen oxides (NOx and NO2) and particulate matter (PM) at the participants' homes at different time periods: during pregnancy, from birth to 3 years, from 3 to 6 years, and from 6 years of age to the age at which the MRI scan was performed. Noise levels due to traffic road were estimated using existing noise maps. Between 9 and 12 years of age, the participants were invited to undergo an MRI scan in the resting state (i.e. with no external stimuli).

The findings show that higher exposures to NO2 and PM2.5 absorbance (an indicator of black carbon particles) from birth to 3 years, and to NOx from 3 to 6 years of age were associated with higher functional brain connectivity among several brain regions in the preadolescents. The associations were identified in brain areas predominantly involved in two networks that have strongly opposing functions: the task negative (or "default-mode") network tends to be activated in resting conditions and the task positive network tends to be activated during tasks that demand attention. "We still have to understand the consequences of this increased activity of both networks in resting conditions, but for now we can say that the brain connectivity in children exposed to higher levels of air pollution is different from what we would expect," says Laura Pérez-Crespo, first author of the study.

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After thousands of years, an iconic whale confronts a new enemy

For millennia, vast expanses of the Arctic Ocean have been untouched by humans, ocean where narwhals and other marine mammals lived undisturbed. Now that climate change is causing sea ice to melt, there has been an uptick of human activity in the Arctic. This has resulted in significantly more noise from an array of human sources, including seismic surveys, mine blasts, port projects and cruise ships.

Although the noise is not violently loud when it comes a from a fair distance, for narwhals, the noise is disturbing and triggers stress -- even many kilometers away. These are the results of unique experiments conducted with the iconic whale. The University of Copenhagen has helped the Greenland Institute of Natural Resources (Pinngortitaleriffik) to analyse the data collected during the research.

Narwhals are notoriously difficult to study because they only live in the hard-to-reach High Arctic, which is often covered by ice. But the research team managed to tag a herd of narwhals in the Scoresby Sound fjord system of East Greenland using a variety of measurement equipment. They then positioned a ship in the fjord, which exposed the animals to noise -- both from the ship's engine and from a seismic airgun used for oil exploration.

"The narwhals' reactions indicate that they are frightened and stressed. They stop emitting the click sounds that they need to feed, they stop diving deep and they swim close to shore, a behaviour that they usually only display when feeling threatened by killer whales. This behavior means that they have no chance of finding food for as long as the noise persists," explains marine biologist Outi Tervo of the Greenland Institute of Natural Resources, who is one of the researchers behind the study.

Researchers can also see that the whales make an uncommon number of strokes with their tails when fleeing from a vessel. This may pose a danger to them because it vastly depletes their energy reserves. Constant energy conservation is important for narwhals as they need a great deal of oxygen to dive several hundred meters below the surface for food and return to the surface for air.

Everything in a narwhal's life is sound

Narwhals spend much of their time in the dark -- partly because the Arctic is dark for half of the year, and partly because these unicorns of the sea hunt at depths of up to 1800 meters, where there is no light. Thus, everything in a narwhal's life is based on sound. And like bats, they orient themselves by echolocation -- which includes emitting click sounds as they hunt.

"Our data shows that narwhals react to noise 20-30 kilometers away from a noise source by completely stopping their clicking sounds. And in one case, we could measure this from a source 40 kilometers away. It is quite surprising that we can measure how something so far away can influence whale behaviour," says Professor Susanne Ditlevsen of the University of Copenhagen's Department of Mathematical Sciences.

Professor Ditlevsen was responsible for the statistical analyses of the enormous and extremely complicated data sets that emerged from the experiments, where data was collected via underwater microphone, GPS, accelerometer (an apparatus that measures movement in three directions) and heart rate monitors. She continues:

"Even when a ship's noise is lower than the background noise in the ocean and we can no longer hear it with our advanced equipment, the whales can hear and distinguish it from other sounds in their midst. And so, to a degree, their behavior is clearly affected. This demonstrates how incredibly sensitive narwhals are."

Following a week of sonic tests, the researchers observed the whales' behavior return to normal again.

"But if they are exposed to noise for a long period of time -- for example, if a port is built nearby that leads to regular shipping traffic, the whales' success in hunting could be affected for a longer period of time, which could become quite serious for them. In this case, we fear that it could have physiological consequences for them and impair their fitness," says Outi Tervo.

Calling upon to authorities

The researchers' hope is that the authorities and other decision-makers will ensure for better management of the activities that create noise pollution in narwhal habitats.

"For the most part, narwhals live around Greenland, Canada and Svalbard in Norway. As such, these countries have the main responsibility for looking after them. Because narwhals are so well-adapted to the Arctic environment, they can't just choose to go to the Caribbean instead. It is being pressured both by warmer water temperatures and in some places, by fish catch. Now, noise enters the equation," says Susanne Ditlevsen.

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Good noise, bad noise: White noise improves hearing

Noise is not the same as noise -- and even a quiet environment does not have the same effect as white noise. With a background of continuous white noise, hearing pure sounds becomes even more precise, as researchers from the University of Basel have shown in a study in Cell Reports. Their findings could be applied to the further development of cochlear implants.

Despite the importance of hearing in human communication, we still understand very little of how acoustic signals are perceived and how they are processed to allow us to make sense of them. One thing is clear though: the more precisely we can distinguish sound patterns, the better our hearing is. But how does the brain manage to distinguish between relevant and less relevant information -- especially in an environment with background noise?

Exploring the "auditory brain"

Researchers led by Prof. Dr. Tania Rinaldi Barkat from the Department of Biomedicine at the University of Basel have investigated the neuronal foundation of sound perception and sound discrimination in a challenging sound environment. The focus was on research into the auditory cortex -- the "auditory brain," that is, the area of the brain that processes acoustic stimuli. The resulting activity patterns stem from measurements in a mouse brain.

As is well known, the distinction between sounds becomes more difficult the closer they are in the frequency spectrum. Initially, the researchers assumed that additional noise could make such a hearing task even more difficult. However, the opposite was observed: The team was able to demonstrate that the brain's ability to distinguish subtle tone differences improved when white noise was added to the background. Compared to a quiet environment, the noise thus facilitated auditory perception.

Noise reduces neuronal activity

The data of the research group showed that white noise significantly inhibited the activity of the nerve cells in the auditory cortex. Paradoxically, this suppression of the neuronal excitation led to a more precise perception of the pure tones. "We found that less overlap occurred between populations of neurons during two separate tone representations," explains Professor Tania Barkat. "As a result, the overall reduction in neuronal activity produced a more distinct tone representation."

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