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GPS-free Navigation May Become a Reality Thanks to a Quantum Compass.
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Posted by Okachinepa on 08/19/2024 @
Courtesy of SynEvol
Credit:Craig Fritz
When you disassemble a smartphone, fitness tracker, or virtual reality headset, you'll discover a tiny motion sensor that records the device's position and motion. With GPS assistance, larger, more costly models of the same technology—roughly the size of a grapefruit and a thousand times more accurate—assist in navigating ships, aircraft, and other vehicles.
Scientists are currently working to create a motion sensor that will be so accurate that it will reduce the country's dependency on global positioning satellites. Such a sensor would have filled a moving truck until recently. It is a thousand times more sensitive than modern navigational equipment. However, developments are bringing this technology's size and cost down significantly.
For the first time, atom interferometry—a quantum sensing method that provides incredibly accurate acceleration measurements—has been carried out by Sandia National Laboratories researchers using silicon photonic microchip components. It is the most recent advancement in the creation of a quantum compass that can be used for navigation in the absence of GPS signals.
Courtesy of SynEvol
Credit: Craig Fritz
The team's research was published, and the journal Science Advances featured a cover story on a novel high-performance silicon photonic modulator—a device that manipulates light on a microchip.
Sandia's Laboratory Directed Research and Development program provided funding for the study. It was partially held at the National Security Photonics Center, a cooperative research facility that creates integrated photonics solutions to challenging issues in the field of national security.
According to Sandia scientist Jongmin Lee, "when GPS signals are unavailable, accurate navigation becomes a challenge in real-world scenarios."
These difficulties present threats to national security in a conflict area since electronic warfare forces have the ability to block or spoof satellite communications, interfering with army movements and activities.
Quantum sensing provides an answer.
"These cutting-edge sensors provide unmatched accuracy in measuring acceleration and angular velocity by harnessing the principles of quantum mechanics, enabling precise navigation even in areas denied GPS service," Lee stated.
An atom interferometer is usually a modest room-sized sensor system. To be more exact, a quantum inertial measurement unit, or full quantum compass, would require six atom interferometers.
However, Lee and his group have been able to lessen the device's size, weight, and power requirements. An avocado-sized vacuum chamber has already taken the place of a big, power-hungry vacuum pump, and multiple parts that were previously painstakingly put across an optical table have been combined into one stiff device.
The novel modulator serves as the focal point of a microchip laser system. It would take the place of a traditional laser system, usually the size of a refrigerator, because it is robust enough to withstand strong vibrations.
In an atom interferometer, lasers serve many purposes. The Sandia team employs four modulators to change the frequency of a single laser so that it can serve various purposes.
However, sidebands—unwanted echoes—that are frequently produced by modulators must be reduced.
By reducing these sidebands by an astonishing 47.8 decibels, a measurement that is frequently used to characterize sound strength but is equally applicable to light intensity, Sandia's suppressed-carrier, single-sideband modulator produces a nearly 100,000-fold decline in light intensity.
Scientist Ashok Kodigala of Sandia remarked, "We have drastically improved the performance compared to what's out there."
Cost has been a significant barrier to the deployment of quantum navigation systems, in addition to size. Each atom interferometer requires a laser system, and modulators are necessary for laser systems.
According to Lee, the cost of a single full-size, commercially available single-sideband modulator is more than $10,000.
Reduced costs are achieved by shrinking large, costly components into silicon photonic chips.
"On a single 8-inch wafer, we can make hundreds of modulators; on a 12-inch wafer, we can make even more," Kodigala stated.
Furthermore, "This sophisticated four-channel component, including additional custom features, can be mass-produced at a much lower cost compared to today's commercial alternatives, enabling the production of quantum inertial measurement units at a reduced cost," according to Lee, because they can be made using the same method as almost all computer chips.
The research team is looking into applications for the technology outside of navigation as field deployment approaches. By sensing the minute changes these make to Earth's gravitational field, researchers are examining if this could aid in the location of subterranean cavities and resources. Additionally, they see applications for the optical components they created, such as the modulator, in optical communications, quantum computing, and LIDAR.
"I find it incredibly thrilling," Kodigala remarked. "Miniaturization is progressing quickly for a wide range of applications."
Kodigala and Lee are the two members of a multidisciplinary team. Experts in nuclear physics and quantum mechanics make up one half of the group, which includes Lee. The other half, including Kodigala, are experts in silicon photonics; picture a microchip with light beams passing through its circuitry in place of electricity.
At the Microsystems Engineering, Science, and Applications complex at Sandia, where researchers design, manufacture, and test chips for use in national security applications, these teams work together.
Quantum sensing scientist at Sandia Peter Schwindt said, "We have colleagues that we can go down the hall and talk to about this and figure out how to solve these key problems for this technology to get it out into the field."
The team's ambitious goal is to transform atom interferometers into a portable quantum compass, which will allow them to close the gap between university basic research and tech businesses' commercial development. An effective instrument for GPS-denied navigation could be an atom interferometer, a well-established technique. The goal of Sandia's continuous work is to increase its fieldability, stability, and profitability.
To create new technologies and assist in the introduction of new goods, the National Security Photonics Center works with academics, government organizations, small and medium-sized enterprises, and industry. To further its goals, Sandia has hundreds of granted patents and several more that are being pursued.
Schwindt remarked, "I'm passionate about seeing these technologies used in practical ways."
The same enthusiasm is shared by Michael Gehl, a scientist at Sandia who works with silicon photonics. He remarked, "It's fantastic to see our photonics chips being used for practical applications."
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A New Brain-Computer Interface Translates Brain Signals Into Speech
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Posted by Okachinepa on 08/15/2024 @
Courtesy of SynEvol
Credit: UC Regents
This ground-breaking system represents a major advancement in neuroprosthetics as it transforms brain impulses into speech with up to 97% accuracy. Casey Harrell, an ALS patient in a clinical trial, was able to successfully use the gadget to regain his capacity to communicate. For those who have lost their capacity to speak, the technology—which uses microelectrode arrays implanted in the brain—has demonstrated amazing outcomes in real-time speech decoding.
UC Davis Health has developed the most accurate brain-computer interface (BCI) device to date, translating brain signals into speech with up to 97% accuracy.
A guy with amyotrophic lateral sclerosis (ALS) who had significantly affected speech had sensors implanted in his brain by the researchers. After setting the system, the individual was able to speak how he meant to in a matter of minutes.
Courtesy of SynEvol
Credit: UC REGENTS
Lou Gehrig's disease, also known as ALS, destroys the nerve cells that regulate movement throughout the body. The illness causes a progressive loss of one's capacity for walking, standing, and hand function. Additionally, it may result in a person losing control over the speech muscles, which could impair their ability to communicate clearly.
The new technology is being created to help those who are paralyzed or suffer from neurological disorders like ALS, so they can communicate again. When the user tries to speak, it can interpret brain signals and translate them into text that the computer will "spoken" aloud.
Neurosurgeon David Brandman of UC Davis said, "Our BCI technology helped a man with paralysis to communicate with friends, families, and caregivers." "The most accurate speech neuroprosthesis (device) ever described is demonstrated in our paper.”
Co-principal investigator and co-senior author Brandman is involved in this research. He is co-director of the UC Davis Neuroprosthetics Lab in addition to being an assistant professor in the department of neurological surgery at UC Davis.
Courtesy of SynEvol
Credit: UC REGENTS
The new brain-computer interface (BCI) technology translates brain activity into letters on a computer screen when a person tries to talk. The text can then be audibly read by the computer.
The group included 45-year-old ALS patient Casey Harrell in the BrainGate clinical trial in order to build the technology. Harrell experienced tetraparesis, or weakness in his arms and legs, at the time of enrollment. Dysarthria made his speech extremely difficult to comprehend, necessitating the assistance of others to interpret for him.
Brandman inserted the experimental BCI device in July 2023. He implanted four microelectrode arrays into the speech coordination region of the brain, the left precentral gyrus. The 256 cortical electrodes on the arrays are intended to record brain activity.
Neuroscientist Sergey Stavisky said, "We're really detecting their attempt to move their muscles and talk." Stavisky works as an assistant professor in the neurological surgery division. He serves as the study's co-principal investigator in addition to being the co-director of the UC Davis Neuroprosthetics Lab. The area of the brain that is attempting to communicate these commands to the muscles is where we are recording. And we are essentially listening to it, converting those brain activity patterns into phonemes, which are similar to syllables or speech units, and then into the words that they are attempting to express.
Courtesy of SynEvol
Credit: UC REGENTS
Although BCI technology has advanced recently, attempts to facilitate communication have been sluggish and error-prone. This is because it took a lot of time and data to run the machine-learning algorithms that deciphered brain signals.
Word mistakes were a common problem with earlier speech BCI systems. This posed a communication barrier and made it challenging for the user to be understood consistently, according to Brandman. "Our goal was to create a system that enabled anyone to be heard at any time they desired to speak."
Harrell employed the approach for both planned and unplanned conversations. Real-time speech decoding was used in all scenarios, and the system was updated often to maintain accuracy.
A screen displayed the words that had been deciphered. Surprisingly, they were read aloud in a voice that resembled Harrell's prior to his ALS diagnosis. Software trained on pre-existing audio clips of his pre-ALS voice was used to compose the voice.
With a 50-word vocabulary, the system required 30 minutes to reach 99.6% word accuracy during the first speech data training session.
He sobbed with delight the first time we used the device since the words he was trying to say correctly showed up on the screen. All of us did, Stavisky remarked.
The number of terms in the prospective vocabulary grew to 125,000 in the second session. With this significantly increased vocabulary, the BCI achieved a 90.2% word accuracy with only 1.4 hours more training data. Following on from ongoing data collecting, the BCI's accuracy has remained at 97.5%.
"At this stage, we can accurately decode what Casey is attempting to say approximately 97% of the time, which is superior to many smartphone applications that are available for purchase that attempt to interpret a person's voice," Brandman stated. "This technology is revolutionary because it gives those who wish to talk but are unable hope. I'm hoping that speech-based cognitive technology will enable sufferers in the future to communicate with their loved ones.
The study covers 32 weeks' worth of data collecting across 84 sessions. Harrell engaged in self-paced, in-person and video chat communication using the speech BCI for more than 248 hours.
It is really annoying and discouraging to be unable to speak. You feel as though you're stuck," Harrell remarked. "This kind of technology will help people reintegrate into society and life."
Lead author Nicholas Card of the study remarked, "It has been incredibly satisfying to watch Casey regain his ability to speak with his family and friends through this technology." Card works as a postdoctoral scholar in the neurological surgery department at UC Davis.
Casey is an incredible person, as are the other BrainGate participants. They should be commended greatly for participating in these early clinical trials. Co-author and sponsor-investigator of the BrainGate trial Leigh Hochberg stated, "They do this not to gain any personal benefit, but to help us develop a system that will restore communication and mobility for other people with paralysis." Hochberg works at Brown University, the VA Providence Healthcare System, Massachusetts General Hospital, and as a neuroscientist.
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Real-Time Brain Activity is Captured by a Two-Photon Microscope
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Posted by Okachinepa on 08/15/2024 @
Courtesy of SynEvol
Credit: Wei Wie and Mei Xueting
A new two-photon fluorescence microscope that can record fast images of brain activity at the cellular level has been created by researchers. With a significantly faster imaging speed and less damage to brain tissue than conventional two-photon microscopy, this new method may help us understand neurological disorders and brain function by giving us a better understanding of how neurons communicate in real time.
Weijian Yang, the head of the University of California, Davis research team, said, "Our new microscope is ideally suited for studying the dynamics of neural networks in real-time, which is crucial for understanding fundamental brain functions such as learning, memory, and decision-making." "For instance, it could be used by researchers to watch neural activity during learning to gain a better understanding of how different neurons communicate and interact with one another during this process."
The researchers disclose the novel two-photon fluorescence microscope in Optica, the high-impact academic magazine published by Optica Publishing Group. It uses line illumination instead of point illumination and features a unique adaptive sampling system. They demonstrate how the novel technique reduces the laser power on the brain by more than ten times and allows for in vivo imaging of neuronal activity in a mouse cortex, all at ten times the speed of conventional two-photon microscopy.
Courtesy of SynEvol
Credit: Wei Wie and Mei Xueting
Yunyang Li, the paper's first author, stated, "Our technology could be used to study the pathology of diseases at their earliest stages by providing a tool that can observe neuronal activity in real-time." "This could aid in the better understanding and treatment of neurological disorders like epilepsy, Parkinson's disease, and Alzheimer's disease by researchers."
By sweeping a small point of light across the entire sample region to stimulate fluorescence and then collecting the resulting signal point by point, two-photon microscopy can examine deeply into scattering tissue, such as a mouse brain. After that, each image frame is captured by repeating this process. Two-photon microscopy can cause harm to brain tissue and is slow, despite providing precise images.
Using a novel sampling technique, the researchers hope to get beyond these constraints in the latest study. Instead of employing a point of light, they highlight particular regions of the brain where neurons are firing with a brief line of light. This greatly accelerates the imaging process by allowing a greater region to be stimulated and photographed simultaneously. Additionally, the overall amount of light energy imparted to the brain tissue is decreased, minimizing the possibility of potential injury, because it only pictures neurons of interest, not the background or inactive areas. This plan was dubbed adaptive sampling.
Courtesy of SynEvol
Credit: Molly M. Bechtel, University of California, Davis
In order to precisely target activated neurons, the researchers used a digital micromirror device (DMD), a chip with thousands of individually controllable small mirrors, to dynamically shape and steer the light beam. By adjusting the on and off states of individual DMD pixels to the neuronal structure of the brain tissue being imaged, they were able to achieve adaptive sampling.
Additionally, the researchers devised a method for simulating high-resolution point scanning using the DMD. This facilitates the reconstruction of a high-resolution image from rapid scans, offering a rapid method for locating neuronal regions of interest. This is essential for the high-speed imaging that follows, which uses an adaptive sampling system and short-line excitation.
The ability to examine dynamic neurological processes in real-time, with less risk to living tissue, is greatly advanced by this strong imaging tool that is the result of several discoveries, each of which is noteworthy on its own, according to Yang. Crucially, our method can be used in conjunction with other methods such as remote focusing and beam multiplexing to accomplish volumetric 3D imaging or to speed up imaging even further.
In order to showcase the novel microscope, the researchers imaged calcium signals in real mouse brain tissue, which are markers of neuronal activity. The system's 198 Hz signal capture rate is noticeably faster than that of conventional two-photon microscopes, indicating its capacity to track quick neuronal events that slower imaging techniques would overlook.
Additionally, they demonstrated how individual neuron activity may be isolated using sophisticated computer techniques in conjunction with the adaptive line-excitation methodology. This is crucial for comprehending the functional architecture of the brain and correctly interpreting intricate neuronal interactions.
Subsequently, the scientists are striving to incorporate voltage imaging functionalities into the microscope to obtain an immediate and highly accurate readout of neuronal activity. In addition, they intend to apply the novel approach to practical neuroscience applications, like monitoring neural activity during learning and investigating brain activity in illness conditions. In order to increase the microscope's usefulness for neurological research, they also want to make it more user-friendly and smaller.
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Fresh Approaches To Enhance Organic Semiconductors
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Posted by Okachinepa on 08/14/2024 @
Courtesy of SynEvol
Credit: Dr. Martin Statz, Sirringhaus Lab
Scientists from Cavendish have found two novel approaches to enhancing organic semiconductors. By using unanticipated features in the non-equilibrium state, they were able to extract more electrons from the material than had previously been conceivable, improving its performance for use in electronic devices.
"Our goal was to precisely identify the process that occurs when polymer semiconductors are heavily doped," stated Dr. Dionisius Tjhe, a postdoctoral research associate at the Cavendish Laboratory. Doping is the technique of boosting a semiconductor's electrical current carrying capacity by either adding or deleting electrons.
Tjhe and his colleagues describe in detail how these new insights may assist to improve the performance of doped semiconductors in a work that was recently published in Nature Materials.
Solids have arranged their electrons into energy bands. Electrical conductivity and chemical bonding are two of the major physical qualities that are governed by the highest-energy band, also known as the valence band. In organic semiconductors, doping is accomplished by taking out a little portion of the valence band's electrons. Then, electricity can flow and conduct through holes, the lack of electrons.
Courtesy of SynEvol
Credit: Sirringhaus Lab
According to Tjhe, "a typical organic semiconductor has only ten to twenty percent of its valence band electrons removed, which is already much higher than the parts per million levels typical in silicon semiconductors." We were able to totally empty the valence band in two of the polymers that we looked at. Surprisingly, we can even remove electrons from the band below in one of these materials. It might be the first time that has happened.
It's interesting to note that the conductivity in the deeper valence band is much higher than in the upper one. It is hoped that deep energy level charge transmission would eventually result in thermoelectric devices with better power. These are responsible for converting heat into electricity, according to co-first author of the paper and postdoctoral research associate at the Cavendish Laboratory, Dr. Xinglong Ren. "We can turn more of our waste heat into electricity and make it a more feasible energy source by finding materials with a higher power output.”
The valence band should be able to empty in other materials, according to the researchers, although polymers may exhibit this behavior the most readily. "We believe that our ability to accomplish this is a result of the arrangement of energy bands in our polymer and the disordered nature of the polymer chains," Tjhe stated. In contrast, because it is more difficult to empty the valence band in these materials, other semiconductors, like silicon, are probably less likely to host similar phenomena. The critical next step is to understand how to replicate this outcome in various materials. For us, this is an exciting moment.
Doping increases the quantity of ions, which restricts the power, while simultaneously increasing the number of holes. Fortunately, by employing an electrode called a field-effect gate, scientists can regulate the number of holes without changing the amount of ions.
"We discovered that we could modify the hole density using the field-effect gate, and this produced very different outcomes," said Dr. Ian Jacobs, a Royal Society University Research Fellow at the Cavendish Laboratory. The natural relationship between conductivity and hole count is for conductivity to rise with increasing hole count and decrease with hole removal. This is shown when we add or remove ions to alter the number of holes. But we observe a different impact when we use the field-effect gate. A conductivity gain always results from adding or deleting holes!
These surprising results were eventually linked by the researchers to a well-known, but infrequently observed, characteristic of disordered semiconductors called a "Coulomb gap." Remarkably, at room temperature, this impact vanishes and the anticipated trend resumes.
According to Jacobs, Coulomb gaps are infamously difficult to detect in electrical tests since they are only apparent when the material is unable to assume its most stable state. However, we were able to observe these effects at significantly higher temperatures—roughly -30°C—than we had originally predicted.
Ren stated, "It turns out that the ions in our material freeze; this can happen at relatively high temperatures." When the ions are frozen, the material is in a non-equilibrium condition if we add or remove electrons. The ions are frozen, which prevents them from rearranging and stabilizing the system as they would like. We can now observe the Coulomb gap as a result.
Thermoelectric power production and conductivity typically trade off with one another, increasing as the other decreases. However, because of the non-equilibrium effects and the Coulomb gap, both can be increased simultaneously, improving performance. The field-effect gate's current restriction is that it only impacts the material's surface. The power and conductivity would rise to even greater heights if the majority of the material was impacted.
While there is certainly room for improvement, the study paper presents a well-defined approach to enhance the efficiency of organic semiconductors. The group has left the door open for additional research into these features, which present great prospects in the energy industry. "This non-equilibrium state of transport has once again shown itself to be a promising pathway toward improved organic thermoelectric devices," Tjhe stated.
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An 80-Year-Old Equation is Surpassed by a New Solar Cell Model.
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Posted by Okachinepa on 08/04/2024 @
Courtesy of SynEvol
By developing a new analytical model, physicists at Åbo Akademi University and Swansea University have made a significant development in solar cell technology. The comprehension and effectiveness of thin-film photovoltaic (PV) devices are improved by this concept.
The electrical current that powers your home or charges the battery bank passes via solar cells, and this process has been explained for almost eight decades by the so-called Shockley diode equation. The latest study, however, casts doubt on this conventional wisdom for a particular class of next-generation solar cells, specifically thin-film solar cells.
These flexible, inexpensive thin-film solar cells' low efficiency has been caused by a number of issues that the current analytical models are unable to adequately account for.
The latest research provides insight into how these solar cells attain maximum efficiency. It demonstrates a crucial equilibrium between storing the energy produced by light and reducing losses from recombination, the process by which electrical charges cancel each other out.
The primary author, Dr. Oskar Sandberg of Åbo Akademi University in Finland, stated, "Our findings provide key insights into the mechanisms driving and limiting charge collection, and ultimately the power-conversion efficiency, in low-mobility PV devices."
A blind area existed in earlier analytical models for these solar cells due to "injected carriers," or charges that entered the device through the connections. These carriers have a major effect on limiting efficiency and recombination.
"Especially for these thin-film cells with low-mobility semiconductors, the traditional models just weren't capturing the whole picture," Swansea University Associate Professor Ardalan Armin, the lead scientist, said. "In order to fill this vacuum, we have developed a new diode equation that takes into consideration these important injected carriers and their recombination with those photogenerated."
"In conventional solar cells, like silicon PV, which is hundreds of times thicker than next-generation thin film PV, like organic solar cells, the recombination between injected charges and photogenerated ones is not a major problem," Dr. Sandberg continued. One of the greatest theoretical physicists of all time, Wolfgang Pauli, famously remarked, "God made the bulk; the surface was the work of the devil."
Associate Professor Armin declared as much. Thin film solar cells are more susceptible to "the work of the devil"—the recombination of valuable photogenerated charges with injected ones near the interface—than standard silicon because they contain substantially larger interfacial regions per bulk.
This novel model provides a new framework for material property analysis, device optimization, and the creation of thinner solar cells and photodetectors with higher efficiency. Additionally, it can help train machines for device optimization, which is a big step forward for the creation of next-generation thin-film solar cells.
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