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  • richardmitnick 4:44 pm on September 18, 2020 Permalink | Reply
    Tags: "Undersea Earthquakes Shake Up Climate Science", , As much as 95 percent of the extra heat trapped on Earth by greenhouse gases is held in the world's oceans., Caltech, Climate Science, , , Listening for the sounds from the many earthquakes that regularly occur under the ocean., Monitoring the temperature of ocean waters has been a priority for climate scientists., Now Caltech researchers have discovered that seismic rumblings on the seafloor can provide them with another tool for doing that., The speed of sound in water increases as the water's temperature rises., These sound waves in the ocean can be clearly recorded by seismometers.   

    From Caltech: “Undersea Earthquakes Shake Up Climate Science” 

    Caltech Logo

    From Caltech

    September 18, 2020
    Emily Velasco
    626‑395‑6487
    evelasco@caltech.edu

    1
    Image Credit : Caltech

    Despite climate change being most obvious to people as unseasonably warm winter days or melting glaciers, as much as 95 percent of the extra heat trapped on Earth by greenhouse gases is held in the world’s oceans. For that reason, monitoring the temperature of ocean waters has been a priority for climate scientists, and now Caltech researchers have discovered that seismic rumblings on the seafloor can provide them with another tool for doing that.

    In a new paper publishing in Science, the researchers show how they are able to make use of existing seismic monitoring equipment, as well as historic seismic data, to determine how much the temperature of the earth’s oceans has changed and continues changing, even at depths that are normally out of the reach of conventional tools.

    They do this by listening for the sounds from the many earthquakes that regularly occur under the ocean, says Jörn Callies, assistant professor of environmental science and engineering at Caltech and study co-author. Callies says these earthquake sounds are powerful and travel long distances through the ocean without significantly weakening, which makes them easy to monitor.

    Wenbo Wu, postdoctoral scholar in geophysics and lead author of the paper, explains that when an earthquake happens under the ocean, most of its energy travels through the earth, but a portion of that energy is transmitted into the water as sound. These sound waves propagate outward from the quake’s epicenter just like seismic waves that travel through the ground, but the sound waves move at a much slower speed. As a result, ground waves will arrive at a seismic monitoring station first, followed by the sound waves, which will appear as a secondary signal of the same event. The effect is roughly similar to how you can often see the flash from lightning seconds before you hear its thunder.

    “These sound waves in the ocean can be clearly recorded by seismometers at a much longer distance than thunder — from thousands of kilometers away,” Wu says. “Interestingly, they are even ‘louder’ than the vibrations traveling deep in the solid Earth, which are more widely used by seismologists.”

    The speed of sound in water increases as the water’s temperature rises, so, the team realized, the length of time it takes a sound to travel a given distance in the ocean can be used to deduce the water’s temperature.

    “The key is that we use repeating earthquakes—earthquakes that happen again and again in the same place,” he says. “In this example we’re looking at earthquakes that occur off Sumatra in Indonesia, and we measure when they arrive in the central Indian ocean. It takes about a half hour for them to travel that distance, with water temperature causing about one-tenth-of-a second difference. It’s a very small fractional change, but we can measure it.”

    Wu adds that because they are using a seismometer that has been in the same location in the central Indian Ocean since 2004, they can look back at the data it collected each time an earthquake occurred in Sumatra, for example, and thus determine the temperature of the ocean at that same time.

    “We are using small earthquakes that are too small to cause any damage or even be felt by humans at all,” Wu says. “But the seismometer can detect them from great distances , thus allowing us to monitor large-scale ocean temperature changes on a particular path in one measurement.”

    Callies says the data they have analyzed confirm that the Indian Ocean has been warming, as other data collected through other methods have indicated, but that it might be warming even faster than previously estimated.

    “The ocean plays a key role in the rate that the climate is changing,” he says. “The ocean is the main reservoir of energy in the climate system, and the deep ocean in particular is important to monitor. One advantage of our method is that the sound waves sample depths below 2,000 meters, where there are very few conventional measurements.”

    Depending on which set of previous data they compare their results to, ocean warming appears to be as much as 69 percent greater than had been believed. However, Callies cautions against drawing any immediate conclusions, as more data need to be collected and analyzed.

    Because undersea earthquakes happen all over the world, Callies says it should be possible to expand the system he and his fellow researchers developed so that it can monitor water temperatures in all of the oceans. Wu adds that because the technique makes use of existing infrastructure and equipment, it is relatively low-cost.

    “We think we can do this in a lot of other regions,” Callies says. “And by doing this, we hope to contribute to the data about how our oceans are warming.”

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 5:08 pm on September 17, 2020 Permalink | Reply
    Tags: "Radio Astronomy in the High Desert", , , “Adding a telescope dish at Owens Valley fills a critical hole in the EHT’s virtual Earth-sized telescope” says Katherine L. (Katie) Bouman of Caltech., , Caltech, Caltech Owens Valley Long Wavelength Array located in high-desert terrain east of California’s Sierra Nevada mountains Altitude 1222 m (4009 ft)., Caltech Owens Valley Radio Observatory OVRO Altitude 1222 m (4009 ft), Caltech’s Deep Synoptic Array 10 dish array at OVRO Altitude 1222 m (4009 ft)., CARMA in the Inyo Mountains east of the OVRO at a site called Cedar Flat 11123 ft (3390 m) ceased operation in 2015 relocated to OVRO Altitude 1222 m (4009 ft)., , , , The Deep Synoptic Array is in the midst of a major upgrade expanding from 10 to 110 radio dishes., The Deep Synoptic Array will get an even more dramatic upgrade with plans to expand to 2000 radio dishes., The night skies flash with intense radio pulses called fast radio bursts (FRBs) whose causes have remained unclear., There is excitment for the project to search for signatures of magnetospheres around planets orbiting other stars.   

    From Caltech: “Radio Astronomy in the High Desert” 

    Caltech Logo

    From Caltech

    Summer 2020, Features
    Whitney Clavin

    1
    The Long Wavelength Array of telescopes at Owens Valley, Altitude 1,222 m (4,009 ft).

    Since 1958, astronomers have unveiled some of the deepest mysteries of the universe with the help of Caltech’s Owens Valley Radio Observatory (OVRO), located in high-desert terrain east of California’s Sierra Nevada mountains. The observatory, which remains at the forefront of radio astronomy, has seen many different projects come and go, including CARMA (Combined Array for Research in Millimeter-wave Astronomy), a hugely successful set of radio telescopes that ceased operations in 2015.

    Combined Array for Research in Millimeter-wave Astronomy (CARMA), in the Inyo Mountains to the east of the Owens Valley Radio Observatory, at a site called Cedar Flat, 11,123 ft (3,390 m), ceased operations in 2015, relocated to Owens Valley Radio Observatory, Altitude 1,222 m (4,009 ft).

    Now, several of those dishes are being repurposed at OVRO, and two other projects, the Deep Synoptic Array and the Long Wavelength Array (LWA), are in the midst of massive expansion efforts.

    Caltech’s Deep Synoptic Array 10 dish array at Owens Valley Radio Observatory, near Big Pine, California USA, Altitude 1,222 m (4,009 ft).

    “OVRO is experiencing a renaissance. We are moving radio astronomy in an entirely new direction,” says Gregg Hallinan, Caltech professor of astronomy and director of OVRO. “By building large numbers of small telescopes, we can scan the skies faster than ever before. These arrays will be generating more than 40 terabytes of science data per day, making them among the most data-intensive telescopes in the world.” The OVRO-LWA project was enabled by a donation from Deborah Castleman (MS ’86) and Harold Rosen (MS ’48, PhD ’51).

    In Search of Magnetospheres

    2
    Marin Anderson (MS ’14, PhD ’19) and Michael Eastwood assemble antennas for the LWA.

    The Long Wavelength Array (LWA) consists of hundreds of pyramid-shaped radio antennas that dot a vast stretch of OVRO. Since 2015, the LWA has used 250 antennas to probe the flickering of radio signals in the night skies, studying everything from the dawn of the universe, to outbursts on our sun, to glowing exoplanets. Now, the National Science Foundation (NSF) is funding an expansion of the project, bringing the total fleet of antennas to 352.

    Hallinan is particularly excited for the project to search for signatures of magnetospheres around planets orbiting other stars. Magnetospheres are the regions around planets dominated by magnetic fields; Earth’s magnetic field protects its atmosphere from erosion by solar wind. The presence of magnetospheres on exoplanets may be a critical ingredient for planetary habitability but have eluded detection to date. “With the LWA, we will scan the entire sky every 10 seconds to monitor thousands of exoplanets simultaneously, waiting for a planet’s magnetosphere to light up in radio waves,” says Hallinan.

    Staring at the Whole Sky

    OVRO hosts several small, focused experiments that target high-risk, high-reward science. A notable example is STARE2 (Survey for Transient Astronomical Radio Emission 2), led by Shri Kulkarni, the George Ellery Hale Professor of Astronomy and Planetary Science at Caltech. The project consists of three radio receivers located at OVRO; at NASA’s Deep Space Network facility in Goldstone, California; and at Delta, Utah.
    The receivers scan broad swaths of the sky every night in search of the brightest fast radio bursts (FRBs). While the receivers are not as sensitive as radio dishes, what they lose in sensitivity, they gain in field of view. In April of this year, STARE2 detected what may be the first-ever FRBs seen in the Milky Way galaxy. The results are preliminary but may provide long-sought proof that FRBs are caused by erupting magnetars, a type of exotic star with powerful magnetic fields.

    Many, Many Dishes

    The night skies flash with intense radio pulses, called fast radio bursts (FRBs), whose causes have remained unclear. One key to unlocking the mystery of these bursts is to identify the galaxies from which they originate. In 2019, the Deep Synoptic Array-10 (DSA-10) at OVRO identified one such host galaxy of an FRB, a rare feat made even more difficult by the fact that this particular FRB did not repeat, as others have been known to do. Now, thanks to new funding from the National Science Foundation (NSF), the DSA is in the midst of a major upgrade, expanding from 10 to 110 radio dishes. The DSA-110 is expected to begin observations in October of this year. “When we begin, we will be identifying about two FRB host galaxies per week,” says Vikram Ravi, assistant professor of astronomy. “That’s a massive sample of galaxies and will help us reveal FRBs’ true nature.” In the future, the DSA will get an even more dramatic upgrade with plans to expand to 2,000 radio dishes. A project funded by Schmidt Futures, called the Radio Camera Initiative, will allow the DSA-2000 to produce images in real time, a first for radio telescopes. According to Ravi, this will make the DSA-2000 “the most powerful radio telescope ever built.”

    3
    Wendy Chen, Nitika Yadlapalli, and Corey Posner assemble a DSA dish.

    A New Purpose

    CARMA [above] , which operated from 2005 to 2015, was one of the most powerful millimeter-wave telescope arrays in the world. (Millimeter waves are considered a type of radio wave.) Located in the Inyo Mountains near Owens Valley, the array consisted of antennas brought together from telescopes across the U.S. to create a combined array of much greater sensitivity. These antennas included the Leighton dishes, named for the late Caltech professor Robert Leighton (BS ’41, MS ’44, PhD ’47), who designed them in the 1970s to kickstart millimeter astronomy at OVRO. After the closure of CARMA, the Leighton dishes were moved back to OVRO. COMAP, which stands for CO Mapping Array Pathfinder, is one of the projects that is repurposing a Leighton dish. Begun in the summer of 2018, this project, led by OVRO associate director Kieran Cleary and professor emeritus Tony Readhead, traces the evolution of galaxies by mapping carbon monoxide (CO), a marker of faint faraway galaxies that are otherwise hard to see. A few of the Leighton dishes are also being combined to form a robotic instrument, known as SPRITE, to determine the nature of some of the most energetic explosions in the universe.

    Another project for which a Leighton dish is being redeployed is the Event Horizon Telescope (EHT), which, in 2019, famously harnessed the power of several radio observatories across the globe to create the first-ever picture of a black hole. Now, with the help of new funding from the NSF, the EHT project is tapping into even more radio telescopes to better image and study black holes. “Adding a telescope dish at Owens Valley fills a critical hole in the EHT’s virtual Earth-sized telescope,” says Katherine L. (Katie) Bouman, an assistant professor of computing and mathematical sciences and electrical engineering who leads the Caltech portion of the international EHT team.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professor. On the committee for the next iteration of the EHT .

    Katie Bouman of Harvard Smithsonian Observatory for Astrophysics, headed to Caltech, with EHT hard drives from Messier 87

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    “This brings us much closer to one day capturing a movie that allows us to track the gas falling into a black hole over the course of a single night.”

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 8:37 am on August 28, 2020 Permalink | Reply
    Tags: "Quantum Innovations Achieved Using Alkaline-Earth Atoms", , , Caltech, ,   

    From Caltech: “Quantum Innovations Achieved Using Alkaline-Earth Atoms” 

    Caltech Logo

    From Caltech

    August 27, 2020
    Whitney Clavin
    (626) 395‑1944
    wclavin@caltech.edu

    Caltech entangled qubits

    In the quest to develop quantum computers, physicists have taken several different paths. For instance, Google recently reported that their prototype quantum computer might have made a specific calculation faster than a classical computer. Those efforts relied on a strategy that involves superconducting materials, which are materials that, when chilled to ultracold temperatures, conduct electricity with zero resistance. Other quantum computing strategies involve arrays of charged or neutral atoms.

    Now, a team of quantum physicists at Caltech has made strides in work that uses a more complex class of neutral atoms called the alkaline-earth atoms, which reside in the second column of the periodic table. These atoms, which include magnesium, calcium, and strontium, have two electrons in their outer regions, or shells. Previously, researchers who experimented with neutral atoms had focused on elements located in the first column of the periodic table, which have just one electron in their outer shells.

    In a paper published in the journal Nature Physics, the researchers demonstrate that they can use individually controlled alkaline-earth atoms to achieve a hallmark of quantum computing: entanglement. This seemingly paradoxical phenomenon occurs when two atoms remain intimately connected even when separated by vast distances. Entanglement is essential to quantum computers because it enables the computers’ internal “switches,” known as qubits, to be correlated with each other and to encode an exponential amount of information.

    “Essentially, we are breaking a two-qubit entanglement record for one of the three leading quantum science platforms: individual neutral atoms,” says Manuel Endres, an assistant professor of physics and leader of the Caltech team. Endres is also a member of one of three new quantum research institutes established by the National Science Foundation’s (NSF’s) Quantum Leap Challenges Institutes program, and a member of one of five new Department of Energy quantum science centers.

    National Quantum Initiative.

    “We are opening up a new tool box for quantum computers and other applications,” says Ivaylo Madjarov, a Caltech graduate student and lead author of the new study. “With alkaline-earth atoms, we have more opportunities for manipulating systems and new opportunities for precise manipulation and readout of the system.”

    To achieve their goal, the researchers turned to optical tweezers, which are basically laser beams that can maneuver individual atoms. The team previously used the same technology to develop a new design for optical atomic clocks. In the new study, the tweezers were used to persuade two strontium atoms within an array of atoms to become entangled.

    “We had previously demonstrated the first control of individual alkaline-earth atoms. In the present work, we have added a mechanism to generate entanglement between the atoms, based on highly excited Rydberg states, in which atoms separated by many microns feel large forces from each other,” says Jacob Covey, a postdoctoral scholar at Caltech. “The unique properties of the alkaline-earth atoms offer new ways to improve and characterize the Rydberg-interaction mechanism.”

    What is more, the researchers were able to create the entangled state with a higher degree of accuracy than had been previously achieved through the use of neutral atoms, and with an accuracy on par with other quantum computing platforms.

    In the future, the researchers hope to expand their ability to control individual qubits, and they plan to further investigate methods to entangle three or more atoms.

    “The endgame is to reach a very high level of entanglement and programmability for many atoms in order to be able to perform calculations that are intractable by a classical computer,” says Endres. “Our system is also suited to investigate how such many-atom entanglement could improve the stability of atomic clocks.”

    The study, published in the August issue of Nature Physics and titled High-fidelity entanglement and detection of alkaline-earth Rydberg atoms, was funded by NSF, the Sloan Foundation, F. Blum, Caltech, the Gordon and Betty Moore Foundation, and the Larson SURF Fellowship. Other authors include, at Caltech: graduate student Adam L. Shaw; Joonhee Choi, IQIM Postdoctoral Scholar in Physics; Anant Kale, laboratory assistant; Alexandre Cooper, former postdoctoral scholar in physics; and Hannes Pichler, former Moore Postdoctoral Scholar in Theoretical Physics; and Vladimir Schkolnik and Jason R. Williams of the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 11:00 am on August 27, 2020 Permalink | Reply
    Tags: "Caltech Faculty to Advance Future Quantum Science Efforts", , Caltech, , LBNL Quantum Systems Accelerator, ORNL Quantum Science Center, White House Office of Science and Technology Policy   

    From Caltech: “Caltech Faculty to Advance Future Quantum Science Efforts” 

    Caltech Logo

    From Caltech

    August 26, 2020
    Whitney Clavin
    (626) 395‑1944
    wclavin@caltech.edu

    LBNL Quantum Systems Accelerator(Image credit: Thor Swift/Berkeley Lab)

    ORNL Quantum Science Center.

    ANL Q-NEXT

    New Department of Energy centers will apply quantum information science to emerging technologies.

    The White House Office of Science and Technology Policy and the U.S. Department of Energy (DOE) have announced funding for five new quantum information science centers across the country, in support of the National Quantum Initiative. Caltech faculty will participate in three of the new science centers: the Quantum Systems Accelerator, led by the Lawrence Berkeley National Laboratory, also known as Berkeley Lab; the Quantum Science Center, led by Oak Ridge National Laboratory; and Q-NEXT, led by Argonne National Laboratory.

    The five new centers will develop cutting-edge quantum technologies for use in a wide range of possible applications including scientific computing; fundamental physics and chemistry research; and the design of solar cells and of new materials and pharmaceuticals. To establish the centers, the Department of Energy is awarding $625 million over five years.

    “The intersection of information science, materials engineering, and quantum technology is an enormous area of opportunity, and one in which we are investing heavily as an institute,” says Caltech president Thomas F. Rosenbaum, the Sonja and William Davidow Presidential Chair and professor of physics. “Caltech researchers, with their comfort moving between disciplines and helping define new fields, are perfect fits for the national DOE effort in quantum materials, quantum computation, and quantum networking.

    The Caltech principal investigator for the Quantum Systems Accelerator is John Preskill, Richard P. Feynman Professor of Theoretical Physics and director of Caltech’s Institute for Quantum Information and Matter (IQIM), who will serve as the scientific coordinator for the center. Other faculty who will participate in the effort include Garnet Chan, Bren Professor of Chemistry; Manuel Endres, assistant professor of physics and Rosenberg Scholar; and Thomas Vidick, professor of computing and mathematical sciences. Caltech faculty who will participate in the Quantum Science Center include Jason Alicea, professor of theoretical physics. Oskar Painter (MS ’95, PhD ’01), the John G Braun Professor of Applied Physics and Physics, will participate in the Q-NEXT center.

    The Quantum Systems Accelerator will pair advanced quantum prototypes—based on neutral atoms, trapped ions, and superconducting circuits—with algorithms specifically constructed for imperfect hardware to demonstrate optimal applications for each platform in scientific computing, materials science, and fundamental physics; the Quantum Science Center will focus on the advancement of topological quantum materials as well as of algorithms and sensors that will enable the manipulation, transfer, and storage of quantum information; and Q-NEXT will focus on communication networks for quantum systems, and on the development of sensors and of quantum simulators and computers to test those systems.

    The Quantum Systems Accelerator, Preskill says, has assembled a group of the top scientists and engineers in the field, including experimental and theoretical physicists, computer scientists, electrical engineers, and theoretical chemists, to develop quantum processors that “will explore the mysterious properties of complex quantum systems in ways never before possible, opening unprecedented opportunities for scientific discovery while also posing new challenges. One of the questions we want to address is: what are the future applications for these devices? We have an idea of what those applications could be, but the possibilities keep shifting as the technology advances and our understanding improves,” he says.

    “Many years ago,” says Alicea, who will participate in the Quantum Science Center, “Alexei Kitaev [Caltech’s Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics] devised an ingenious idea for exploiting novel phases of matter to build inherently error-resistant quantum computers. One of the center’s aims is to bring that idea to experimental life. We will develop new road maps toward that end goal and hopefully discover lots of interesting physics along the way.”

    Painter, a member of the Q-NEXT center team says, “Q-NEXT brings together scientists and engineers to develop the materials and devices for constructing large-scale networks in which information can be distributed using quantum entanglement, a special property of nature usually only observed at the atomic scale. These networks, representing a form of quantum internet, would embody a manifestation of quantum mechanics at a truly massive scale, with the potential of realizing new methods of securely sharing information, performing distributed computations, or deploying arrays of sensors.”

    More information can be found in news releases about the Quantum Systems Accelerator, the Quantum Science Center, and Q-NEXT.

    Additional information is in a DOE news release.

    See the full article here.

    White House Office of Science and Technology Policy

    National Quantum Initiative.


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 4:10 pm on August 20, 2020 Permalink | Reply
    Tags: "Photoacoustic Microscopy System Boosts Imaging Speed", Caltech, , Pulsed laser technology   

    From Optics & Photonics: “Photoacoustic Microscopy System Boosts Imaging Speed” 

    From Optics & Photonics

    20 August 2020
    Meeri Kim

    1
    Multifocal optical-resolution photoacoustic microscopy through an ergodic relay (MFOR-PAMER) shortens the scanning time while maintaining a simple and economic setup. [Image: Yang Li, Terence T. W. Wong, Junhui Shi, Hsun-Chia Hsu and Lihong V. Wang]

    Because light scatters so strongly in biological tissues, purely optical imaging techniques have a short leash when it comes to probing depths beneath the surface. Sound scatters a thousand times less than light in these situations, which has led scientists to develop hybrid optical-acoustic imaging methods.

    Researchers at the California Institute of Technology, USA, report on one of these hybrid methods, a new variation of a photoacoustic microscopy system that is faster, smaller, and cheaper than others of its kind [Nature Light Science and Applications].

    It can reduce the imaging time of a histology sample from several hours to less than a minute, paving the way for rapid, label-free diagnoses of cancer and other diseases.

    Low complexity, high resolution

    Photoacoustic microscopy uses a pulsed laser to illuminate a sample, which heats up the molecules inside. The rise in temperature leads to thermoelastic expansion of the tissue, generating acoustic waves that can be detected by ultrasonic transducers. The result is a map of optical absorption within the sample, which depends on the concentrations of things like hemoglobin, water or lipids.

    For the current study, OSA Fellow Lihong V. Wang and his colleagues wanted to develop a new type of photoacoustic microscopy system that combined a fast imaging speed with low complexity and cost. A method previously created by Wang’s group, called multifocal optical-resolution photoacoustic tomography (MFOR-PACT), boosted imaging speed by adding a microlens array with multiple optical foci and an ultrasonic transducer array to a traditional setup. These modifications got rid of the bottleneck of slow mechanical scanning across the sample to form an image.

    “Applications of the MFOR-PACT system were limited because of the size and complexity of the array-based photoacoustic tomography system,” said Yang Li, the study’s first author.

    Improving scanning time

    The solution was to replace the array-based design with one that used a single-element ultrasonic transducer through an ergodic relay, which scrambles acoustic pulses based on their origin. A light-transparent, right-angle prism served as the ergodic relay that could then collect photoacoustic signals from the entire field-of-view with a single laser shot.

    Li and his colleagues validated the new technique, called multifocal optical-resolution photoacoustic microscopy through an ergodic relay (MFOR-PAMER), with in vitro and in vivo experiments. For example, they successfully imaged blood vessels in a mouse ear with an optical resolution of 13 microns. In addition, MFOR-PAMER achieves a 400-fold improvement in scanning time compared with a traditional photoacoustic microscopy system at the same resolution.

    “One of the useful applications that we envisioned is using UV illumination for high-speed, label-free histological study of biological tissues,” said Li. “A conventional UV-based optical-resolution photoacoustic microscopy system required several hours to image a histology sample. Our system can potentially reduce the imaging time to less than a minute, which will be a significant improvement in efficiency in clinical settings.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Optics and Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics. We welcome your submissions.

     
  • richardmitnick 8:13 am on August 19, 2020 Permalink | Reply
    Tags: "ZTF Finds Closest Known Asteroid to Fly By Earth", Asteroid 2020 QG, , , , Caltech,   

    From Caltech: “ZTF Finds Closest Known Asteroid to Fly By Earth” 

    Caltech Logo

    From Caltech

    August 18, 2020

    Whitney Clavin
    (626) 395‑1944
    wclavin@caltech.edu

    1
    This is the first image of Asteroid 2020 QG, captured by Caltech’s Zwicky Transient Facility (ZTF) after the asteroid’s closest approach to Earth at a distance of 1,830 miles above the planet’s surface. The asteroid shows up as a streak because it is closer than the background stars, and zipped past ZTF’s camera. Credit: ZTF/Caltech Optical Observatories.

    2
    This simulation image shows how Earth’s gravity bent the path of Asteroid 2020 QG. The green line indicates the object’s apparent motion relative to Earth, and the bright green marks are the object’s location at approximately half-hour intervals. The Moon’s orbit is grey. The blue arrow points in the direction of Earth’s motion and the yellow arrow points toward the sun. Credit: MPC.

    Zwicky Transient Facility (ZTF) instrument installed on the 1.2m diameter Samuel Oschin Telescope at Palomar Observatory in California. Courtesy Caltech Optical Observatories

    Caltech Palomar Samuel Oschin 48 inch Telescope, located in San Diego County, California, United States, altitude 1,712 m (5,617 ft)

    On August 16, the Zwicky Transient Facility (ZTF), a robotic survey camera located at Palomar Observatory near San Diego, spotted an asteroid that had, just hours earlier, traveled only 1,830 miles (2,950 kilometers) above Earth’s surface. Designated 2020 QG, it is the closest known asteroid to fly by Earth without impacting the planet. The previous known record-holder is asteroid 2011 CQ1, discovered by the Catalina Sky Survey in 2011, which passed above Earth about 1,550 miles (2,500 kilometers) higher than 2020 QG.

    Asteroid 2020 QG is about 10 to 20 feet (3 to 6 meters) across, or roughly the size of an SUV, so it was not big enough to do any damage even if it had been pointed at Earth; instead, it would have burned up in our planet’s atmosphere.

    “The asteroid flew close enough to Earth that Earth’s gravity significantly changed its orbit,” says ZTF co-investigator Tom Prince, the Ira S. Bowen Professor of Physics at Caltech and a senior research scientist at JPL, which Caltech manages for NASA. Asteroids of this size that fly roughly as close to Earth as 2020 QG do occur about once a year or less, but many of them are never detected.

    “ZTF’s large-field of view and rapid data processing allows it to find rare asteroids like this that other telescopes might not find,” says George Helou, ZTF co-investigator and director of IPAC, an astronomy center, at Caltech.

    ZTF, which is funded by the National Science Foundation (NSF) and other collaborators, scans the entire northern sky every three nights in search of supernovas, erupting stars, and other objects that otherwise change or move in the sky. As part of a NASA-funded program, ZTF team members search for near-Earth asteroids. When these space rocks speed across the sky, they leave streaks in the ZTF images. Each night, machine-learning programs automatically sort through about 100,000 images in search of these streaks, and then narrow down the best asteroid candidates to be followed up by humans. This results in about 1,000 images that team members and students sort through by eye every day.

    Asteroid 2020 QG was identified by Kunal Deshmukh, a student at the Indian Institute of Technology Bombay. Deshmukh had been scanning that day’s images along with Kritti Sharma, also at the Indian Institute of Technology Bombay, and Chen-Yen Hsu at National Central University in Taiwan.

    “A lot of the streaks are satellites, but we can quickly go through the best images by eye to find the actual asteroids,” says Bryce Bolin, postdoctoral scholar in astronomy at Caltech and a member of the ZTF team, who regularly hunts for asteroids. “This latest find really demonstrates that ZTF can be used to locate objects very close to Earth that are on potentially impacting trajectories.”

    After the ZTF team reported their finding to the International Astronomical Union Minor Planet Center, several telescopes followed up to learn more about the asteroid’s size and orbit.

    Caltech’s ZTF is funded by the NSF and an international collaboration of partners. Additional support comes from the Heising-Simons Foundation and from Caltech. ZTF data are processed and archived by IPAC. NASA supports ZTF’s search for near-Earth objects through the Near-Earth Object Observations program.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 11:26 am on August 13, 2020 Permalink | Reply
    Tags: "Analysis of Renewable Energy Points Policy Makers to Path Toward More Affordable and Reliable Carbon-Free Electricity", , Caltech, , ,   

    From Caltech: “Analysis of Renewable Energy Points Policy Makers to Path Toward More Affordable and Reliable Carbon-Free Electricity” 

    Caltech Logo

    From Caltech

    August 06, 2020
    Emily Velasco
    626‑395‑6487
    evelasco@caltech.edu

    1
    Wind farm. Caltech.

    As more states in the U.S. push for increased reliance on variable renewable energy in the form of wind or solar power, long-term energy storage may play an important role in assuring reliability and reducing electricity costs, according to a new paper published by Caltech researchers.

    Graduate student Jackie Dowling, who works in the lab of Nathan Lewis (BS ’77), the George L. Argyros Professor and professor of chemistry, has collaborated with Ken Caldeira at the Carnegie Institution for Science and others to examine energy-storage options and multiple decades of data about wind and solar availability. Dowling and her collaborators determined that currently available battery technology is prohibitively expensive for long-term energy storage services for the power grid and that alternative technologies that can store a few weeks’ to a month’s worth of energy for entire seasons or even multiple years may be the key to building affordable, reliable renewable electricity systems.

    Energy storage is needed with renewable energy because wind and solar energy are not as reliably available as fossil fuels. For example, wind power is often at its lowest during the summer in the United States, which is when the electrical grid is strained the most by the demand for air conditioning in homes and businesses.

    “This research is motivated by the fact that laws in several states have mandated 100 percent carbon-free electricity systems by midcentury,” says Dowling, lead author of a paper about the work. “Within these mandates, a lot of states include requirements for wind and solar power. Both wind and solar are variable from day to day, or even year to year, yet high reliability is mandatory for a viable electricity system. Energy storage can fill in for the gaps between supply and demand.”

    Dowling looked at short-duration storage systems, such as lithium-ion batteries, and long-duration storage methods, such as hydrogen storage, compressed-air storage, and pumped-storage hydroelectricity.

    To see how to optimize the use of those storage technologies at the lowest energy cost, Dowling built a mathematical simulation of each and incorporated historical electricity-demand data and four decades of hourly resolved historical weather data across the contiguous U.S. The Macro Energy Model, as she calls it, reveals that adding long-duration storage to a wind–solar-battery system lowers energy costs. In contrast, using batteries alone for storage makes renewable energy more expensive.

    Dowling says that the extra expense associated with batteries occurs because they cannot cost-effectively store enough energy for an entire season during which electricity is generated in lower amounts. That means an electrical grid would require many costlier solar panels or wind turbines to compensate and would result in wasteful idling of electricity-generation equipment for much of the year.

    Currently available battery technology is not close to being cost effective for seasonal storage, Dowling says.

    “The huge dip in wind power in the summer in the U.S. is problematic, and batteries are not suitable for filling that gap. So, if you only have batteries, you have to overbuild wind or solar capacity,” she says. “Long-duration storage helps avoid the need to overbuild power generation infrastructure and provides electricity when people need it rather than only when nature provides it. At current technology costs, storage in underground caverns of green hydrogen generated by water electrolysis would provide a cost-effective approach for long-duration grid storage.”

    Other researchers have built renewable energy models, but the team’s data-driven approach is the first to incorporate four decades of historical wind and solar variability data, thus factoring in variability from year to year and periodic episodes of rare weather events that affect power generation, such as wind and solar droughts.

    “The more years of data we use in our models, the more we find a compelling need for long-term storage to get the reliability that we expect from an electricity system,” she says.

    Dowling suggests her findings may be helpful to policy makers in states with 100 percent carbon-free electricity laws and high wind/solar mandates and to other U.S. states considering the adoption of similar laws. In the future, she plans to extend her research to take an in-depth look at the roles that specific types of energy storage, such as hydrogen or redox flow batteries, can play in renewable energy systems. For instance, some types of batteries might effectively serve as medium-duration energy storage, she says.

    The paper, titled Role of long-duration energy storage in variable renewable electricity systems, appears in the September issue of Joule. Co-authors are Lewis and Katherine Rinaldi, chemistry graduate student, of Caltech; Tyler Ruggles, Mengyao Yuan, and Ken Caldeira of the Carnegie Institution for Science; Steven Davis of UC Irvine; and Fan Tong of the Carnegie Institution for Science and Lawrence Berkeley National Laboratory.

    Support for the research was provided by the Resnick Sustainability Institute at Caltech, through which Dowling is a Zeller-Resnick Fellow; the Gordon and Betty Moore Foundation; a fellowship from the Southern California Gas Company; and through a gift from Gates Ventures LLC to the Carnegie Institution for Science.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 9:08 am on July 29, 2020 Permalink | Reply
    Tags: "A method to predict the properties of complex quantum systems", Caltech, , Machines are currently unable to support quantum systems with over tens of qubits., , , Quantum state tomography, Unitary t-design   

    From Caltech via phys.org: “A method to predict the properties of complex quantum systems” 

    Caltech Logo

    From Caltech

    via


    phys.org

    July 29, 2020
    Ingrid Fadelli

    1
    Credit: Huang, Kueng & Preskill.

    Predicting the properties of complex quantum systems is a crucial step in the development of advanced quantum technologies. While research teams worldwide have already devised a number of techniques to study the characteristics of quantum systems, most of these have only proved to be effective in some cases.

    Three researchers at California Institute of Technology recently introduced a new method that can be used to predict multiple properties of complex quantum systems from a limited number of measurements. Their method, outlined in a paper published in Nature Physics, has been found to be highly efficient and could open up new possibilities for studying the ways in which machines process quantum information.

    “During my undergraduate, my research centered on statistical machine learning and deep learning,” Hsin-Yuan Huang, one of the researchers who carried out the study, told Phys.org. “A central basis for the current machine-learning era is the ability to use highly parallelized hardware, such as graphical processing units (GPU) or tensor processing units (TPU). It is natural to wonder how an even more powerful learning machine capable of harnessing quantum-mechanical processes could emerge in the far future. This was my aspiration when I started my Ph.D. at Caltech.”

    The first step toward the development of more advanced machines based on quantum-mechanical processes is to gain a better understanding of how current technologies process and manipulate quantum systems and quantum information. The standard method for doing this, known as quantum state tomography, works by learning the entire description of a quantum system. However, this requires an exponential number of measurements, as well as considerable computational memory and time.

    As a result, when using quantum state tomography, machines are currently unable to support quantum systems with over tens of qubits. In recent years, researchers have proposed a number of techniques based on artificial neural networks that could significantly enhance the quantum information processing of machines. Unfortunately, however, these techniques do not generalize well across all cases, and the specific requirements that allow them to work are still unclear.

    “To build a rigorous foundation for how machines can perceive quantum systems, we combined my previous knowledge about statistical learning theory with Richard Kueng and John Preskill’s expertise on a beautiful mathematical theory known as unitary t-design,” Huang said. “Statistical learning theory is the theory that underlies how the machine could learn an approximate model about how the world behaves, while unitary t-design is a mathematical theory that underlies how quantum information scrambles, which is central to understand quantum many-body chaos, in particular, quantum black holes.”

    By combining statistical learning and unitary t-design theory, the researchers were able to devise a rigorous and efficient procedure that allows classical machines to produce approximate classical descriptions of quantum many-body systems. These descriptions can be used to predict several properties of the quantum systems that are being studied by performing a minimal number of quantum measurements.

    “To construct an approximate classical description of the quantum state, we perform a randomized measurement procedure given as follows,” Huang said. “We sample a few random quantum evolutions that would be applied to the unknown quantum many-body system. These random quantum evolutions are typically chaotic and would scramble the quantum information stored in the quantum system.”

    The random quantum evolutions sampled by the researchers ultimately enable the use of the mathematical theory of unitary t-design to study such chaotic quantum systems as quantum black holes. In addition, Huang and his colleagues examined a number of randomly scrambled quantum systems using a measurement tool that elicits a wave function collapse, a process that turns a quantum system into a classical system. Finally, they combined the random quantum evolutions with the classical system representations derived from their measurements, producing an approximate classical description of the quantum system of interest.

    “Intuitively, one could think of this procedure as follows,” Huang explained. “We have an exponentially high-dimensional object, the quantum many-body system, that is very hard to grasp by a classical machine. We perform several random projections of this extremely high-dimension object to a much lower dimensional space through the use of random/chaotic quantum evolution. The set of random projections provides a rough picture of how this exponentially high dimensional object looks, and the classical representation allows us to predict various properties of the quantum many-body system.”

    Huang and his colleagues proved that by combining statistical learning constructs and the theory of quantum information scrambling, they could accurately predict M properties of a quantum system based solely on log(M) measurements. In other words, their method can predict an exponential number of properties simply by repeatedly measuring specific aspects of a quantum system for a specific number of times.

    “The traditional understanding is that when we want to measure M properties, we have to measure the quantum system M times,” Huang said. “This is because after we measure one property of the quantum system, the quantum system would collapse and become classical. After the quantum system has turned classical, we cannot measure other properties with the resulting classical system. Our approach avoids this by performing randomly generated measurements and infer the desired property by combining these measurement data.”

    The study partly explains the excellent performance achieved by recently developed machine learning (ML) techniques in predicting properties of quantum systems. In addition, its unique design makes the method they developed significantly faster than existing ML techniques, while also allowing it to predict properties of quantum many-body systems with a greater accuracy.

    “Our study rigorously shows that there is much more information hidden in the data obtained from quantum measurements than we originally expected,” Huang said. “By suitably combining these data, we can infer this hidden information and gain significantly more knowledge about the quantum system. This implies the importance of data science techniques for the development of quantum technology.”

    The results of tests the team conducted suggest that to leverage the power of machine learning, it is first necessary to attain a good understanding of intrinsic quantum physics mechanisms. Huang and his colleagues showed that although directly applying standard machine-learning techniques can lead to satisfactory results, organically combining the mathematics behind machine learning and quantum physics results in far better quantum information processing performance.

    “Given a rigorous ground for perceiving quantum systems with classical machines, my personal plan is to now take the next step toward creating a learning machine capable of manipulating and harnessing quantum-mechanical processes,” Huang said. “In particular, we want to provide a solid understanding of how machines could learn to solve quantum many-body problems, such as classifying quantum phases of matter or finding quantum many-body ground states.”

    This new method for constructing classical representations of quantum systems could open up new possibilities for the use of machine learning to solve challenging problems involving quantum many-body systems. To tackle these problems more efficiently, however, machines would also need to be able to simulate a number of complex computations, which would require a further synthesis between the mathematics underlying machine learning and quantum physics. In their next studies, Huang and his colleagues plan to explore new techniques that could enable this synthesis.

    “At the same time, we are also working on refining and developing new tools for inferring hidden information from the data collected by quantum experimentalists,” Huang said. “The physical limitation in the actual systems provides interesting challenges for developing more advanced techniques. This would further allow experimentalists to see what they originally could not and help advance the current state of quantum technology.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 9:44 am on July 16, 2020 Permalink | Reply
    Tags: "Superconducting Twisted Bilayer Graphene—Magic not Needed? ", , Caltech, , , Superconductivity at angles relatively far from the magic angle and it does not change into an insulator at any electron density breaking the pattern., Superconductivity can be stabilized by tailoring the environment of the graphene layers., Superconductivity in twisted bilayer graphene can exist away from the magic angle when coupled to a two-dimensional semiconductor., The specific twist angle at which this occurs was nicknamed the "magic angle-1.05 degrees rotation.   

    From Caltech: “Superconducting Twisted Bilayer Graphene—Magic not Needed? “ 

    Caltech Logo

    From Caltech

    1
    A scanning tunneling microscopy topographic image of twisted bilayer graphene, Credit S. Nadj-Perge.

    New study shows that superconductivity in twisted bilayer graphene can exist away from the magic angle when coupled to a two-dimensional semiconductor.

    In 2018, researchers made the surprising discovery that when you layer two sheets of single-atom-thick graphene atop one another and rotate them by precisely 1.05 degrees with respect to one another, the resulting bilayer material takes on new properties: when the density of electrons in the material is increased through the application of a voltage on a nearby electrode, it becomes a superconductor—electrons can flow freely through the material, without resistance. However, with a slight change in electron density, the bilayer becomes an insulator and prevents the flow of electrons.

    The specific twist angle at which this occurs was nicknamed the “magic angle,” and its discovery jumpstarted interest in a branch of physics known as twistronics. The electron densities that turn the material into a superconductor or an insulator are very close to one another, so the central question of bilayer graphene twistronics has become to understand why these states—insulators and superconductors—are so intimately related.

    Now, a team at Caltech has discovered that when twisted bilayer graphene is placed in contact with a single-atom-thick material that contains the heavy element tungsten, it can exhibit superconductivity at angles relatively far from the magic angle, and it does not change into an insulator at any electron density, breaking the pattern. Their work was published in the journal Nature on July 15.

    What does it mean to have insulators and superconductors occurring at similar electron densities, and why is this important?

    When studying how materials conduct electricity, physicists often talk about a phase diagram, a plot that represents resistance as a function of electrondensity (on one axis) and temperature (on the other). In this phase diagram for magic angle-twisted bilayer graphene, the superconducting phase and the insulating phase are adjacent on the electron-density axis. Both the superconductivity and insulating states in magic angle-twisted bilayers of graphene occur only at cryogenic temperatures, a fraction of a degree above absolute zero (−273.15 degrees Celsius). But back in the 1980s, a similar phase diagram was noted in so-called high-temperature superconductors that operate at a much higher temperature—one to two hundred degrees above absolute zero, which is still cold, but not as cold as was thought to be needed to generate the superconducting and insulating states in twisted graphene.

    “Physicists got very excited about this discovery, thinking that if these two systems are indeed similar, then perhaps studying twisted bilayer graphene could teach us something about high-temperature superconductivity,” says Stevan Nadj-Perge, corresponding author of the paper and assistant professor of applied physics and materials science at Caltech. “Our new findings, however, question that similarity.”

    To achieve the magic angle usually requires such extreme precision in the placement of the two graphene sheets that only a few out of many samples will show the signature of superconductivity. The new approach developed at Caltech relaxes these stringent requirements. In the method, the graphene sheets are placed on top of another two-dimensional material that contains tungsten and selenide, called tungsten-diselenide (WSe2). The presence of tungsten enhances the coupling between an electron’s “spin” (a property of subatomic particles that describes how they interact with magnetic fields) and its motion. The so-called spin–orbit coupling that is induced in twisted bilayer graphene may explain the stabilization of superconductivity.

    When the additional WSe2 layers were used, the Caltech team found, superconductivity could exist even when insulating states were entirely absent. “This shows that superconductivity can be stabilized by tailoring the environment of the graphene layers,” Nadj-Perge says.

    “While we did observe signatures of spin–orbit coupling in our samples, whether this coupling is responsible for stabilization of superconductivity is still an open question. At this point, it is too early to say conclusively,” Nadj-Perge says. “Our observations were quite unexpected. It implies that we only scratched the surface of graphene twistronics. These are exciting times for the field.”

    The paper is titled Superconductivity in metallic twisted bilayer graphene stabilized by WSe2. Co-authors include Jason Alicea, professor of theoretical physics at Caltech; Caltech graduate students Harpreet Arora (PhD ’20), Robert Polski, and Yiran Zhang (all of whom are leading authors on the paper); graduate students Youngjoon Choi and Hyunjin Kim; Alex Thomson, Sherman Fairchild Postdoctoral Scholar in Theoretical Physics at Caltech; Zhong Lin, Ilham Zaky Wilson, Xiaodong Xu, and Jiun-Haw Chu of the University of Washington, who provided WSe2 crystals; and Kenji Watanabe and Takashi Taniguchi of the National Institute for Materials Science in Japan.

    The research at Caltech was funded by the National Science Foundation, the United States Department of Energy, the Caltech-Gist memorandum of understanding program, the Kavli Nanoscience Institute, the Institute for Quantum Information and Matter at Caltech, the Walter Burke Institute for Theoretical Physics at Caltech, and the Kwanjeong Educational Foundation.


    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus

     
  • richardmitnick 11:33 am on July 7, 2020 Permalink | Reply
    Tags: "Quantum fluctuations can jiggle objects on the human scale", Caltech, , , ,   

    From MIT News and Caltech: “Quantum fluctuations can jiggle objects on the human scale” 

    Caltech Logo

    From Caltech

    and

    MIT News

    MIT News

    July 1, 2020
    Jennifer Chu

    1
    MIT physicists have observed that LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects. In this photo, a LIGO optics technician inspects one of LIGO’s mirrors. Credit: Matt Heintze/Caltech/MIT/LIGO Lab

    Study shows LIGO’s 40-kilogram mirrors can move in response to tiny quantum effects, revealing the “spooky popcorn of the universe.”

    The universe, as seen through the lens of quantum mechanics, is a noisy, crackling space where particles blink constantly in and out of existence, creating a background of quantum noise whose effects are normally far too subtle to detect in everyday objects.

    Now for the first time, a team led by researchers at MIT LIGO Laboratory has measured the effects of quantum fluctuations on objects at the human scale. In a paper published today in Nature, the researchers report observing that quantum fluctuations, tiny as they may be, can nonetheless “kick” an object as large as the 40-kilogram mirrors of the U.S. National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), causing them to move by a tiny degree, which the team was able to measure.


    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project


    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    It turns out the quantum noise in LIGO’s detectors is enough to move the large mirrors by 10^20 meters — a displacement that was predicted by quantum mechanics for an object of this size, but that had never before been measured.

    “A hydrogen atom is 10^10 meters, so this displacement of the mirrors is to a hydrogen atom what a hydrogen atom is to us — and we measured that,” says Lee McCuller, a research scientist at MIT’s Kavli Institute for Astrophysics and Space Research.

    The researchers used a special instrument that they designed, called a quantum squeezer, to “manipulate the detector’s quantum noise and reduce its kicks to the mirrors, in a way that could ultimately improve LIGO’s sensitivity in detecting gravitational waves,” explains Haocun Yu, a physics graduate student at MIT.

    “What’s special about this experiment is we’ve seen quantum effects on something as large as a human,” says Nergis Mavalvala, the Marble Professor and associate head of the physics department at MIT. “We too, every nanosecond of our existence, are being kicked around, buffeted by these quantum fluctuations. It’s just that the jitter of our existence, our thermal energy, is too large for these quantum vacuum fluctuations to affect our motion measurably. With LIGO’s mirrors, we’ve done all this work to isolate them from thermally driven motion and other forces, so that they are now still enough to be kicked around by quantum fluctuations and this spooky popcorn of the universe.”

    Yu, Mavalvala, and McCuller are co-authors of the new paper, along with graduate student Maggie Tse and Principal Research Scientist Lisa Barsotti at MIT, along with other members of the LIGO Scientific Collaboration.

    A quantum kick

    LIGO is designed to detect gravitational waves arriving at the Earth from cataclysmic sources millions to billions of light years away. It comprises twin detectors, one in Hanford, Washington, and the other in Livingston, Louisiana. Each detector is an L-shaped interferometer made up of two 4-kilometer-long tunnels, at the end of which hangs a 40-kilogram mirror.

    To detect a gravitational wave, a laser located at the input of the LIGO interferometer sends a beam of light down each tunnel of the detector, where it reflects off the mirror at the far end, to arrive back at its starting point. In the absence of a gravitational wave, the lasers should return at the same exact time. If a gravitational wave passes through, it would briefly disturb the position of the mirrors, and therefore the arrival times of the lasers.

    Much has been done to shield the interferometers from external noise, so that the detectors have a better chance of picking out the exceedingly subtle disturbances created by an incoming gravitational wave.

    Mavalvala and her colleagues wondered whether LIGO might also be sensitive enough that the instrument might even feel subtler effects, such as quantum fluctuations within the interferometer itself, and specifically, quantum noise generated among the photons in LIGO’s laser.

    “This quantum fluctuation in the laser light can cause a radiation pressure that can actually kick an object,” McCuller adds. “The object in our case is a 40-kilogram mirror, which is a billion times heavier than the nanoscale objects that other groups have measured this quantum effect in.”

    Noise squeezer

    To see whether they could measure the motion of LIGO’s massive mirrors in response to tiny quantum fluctuations, the team used an instrument they recently built as an add-on to the interferometers, which they call a quantum squeezer. With the squeezer, scientists can tune the properties of the quantum noise within LIGO’s interferometer.

    The team first measured the total noise within LIGO’s interferometers, including the background quantum noise, as well as “classical” noise, or disturbances generated from normal, everyday vibrations. They then turned the squeezer on and set it to a specific state that altered the properties of quantum noise specifically. They were able to then subtract the classical noise during data analysis, to isolate the purely quantum noise in the interferometer. As the detector constantly monitors the displacement of the mirrors to any incoming noise, the researchers were able to observe that the quantum noise alone was enough to displace the mirrors, by 10^20 meter.

    Mavalvala notes that the measurement lines up exactly with what quantum mechanics predicts. “But still it’s remarkable to see it be confirmed in something so big,” she says.

    Going a step further, the team wondered whether they could manipulate the quantum squeezer to reduce the quantum noise within the interferometer. The squeezer is designed such that when it set to a particular state, it “squeezes” certain properties of the quantum noise, in this case, phase and amplitude. Phase fluctuations can be thought of as arising from the quantum uncertainty in the light’s travel time, while amplitude fluctuations impart quantum kicks to the mirror surface.

    “We think of the quantum noise as distributed along different axes, and we try to reduce the noise in some specific aspect,” Yu says.

    When the squeezer is set to a certain state, it can for example squeeze, or narrow the uncertainty in phase, while simultaneously distending, or increasing the uncertainty in amplitude. Squeezing the quantum noise at different angles would produce different ratios of phase and amplitude noise within LIGO’s detectors.

    The group wondered whether changing the angle of this squeezing would create quantum correlations between LIGO’s lasers and its mirrors, in a way that they could also measure. Testing their idea, the team set the squeezer to 12 different angles and found that, indeed, they could measure correlations between the various distributions of quantum noise in the laser and the motion of the mirrors.

    Through these quantum correlations, the team was able to squeeze the quantum noise, and the resulting mirror displacement, down to 70 percent its normal level. This measurement, incidentally, is below what’s called the standard quantum limit, which, in quantum mechanics, states that a given number of photons, or, in LIGO’s case, a certain level of laser power, is expected to generate a certain minimum of quantum fluctuations that would generate a specific “kick” to any object in their path.

    By using squeezed light to reduce the quantum noise in the LIGO measurement, the team has made a measurement more precise than the standard quantum limit, reducing that noise in a way that will ultimately help LIGO to detect fainter, more distant sources of gravitational waves.

    This research was funded, in part, by the National Science Foundation.

    See the full article here .


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    Please help promote STEM in your local schools.


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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

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