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  • richardmitnick 11:29 am on January 12, 2020 Permalink | Reply
    Tags: A novel type of detector that enables the oscillation profile of light waves to be precisely determined., , Laboratory for Attosecond Physics at Ludwig-Maximilians-Universitaet, Laser Technology, , ,   

    Max Planck Institute of Quantum Optics via phys.org: “Laser physics- At the pulse of a light wave” 

    Max Planck Institute of Quantum Optics

    Max Planck Institute of Quantum Optics

    via


    phys.org

    January 10, 2020
    Ludwig Maximilian University of Munich

    1
    How a novel type of detector enables the oscillation profile of light waves to be precisely determined. Credit: Philipp Rosenberger

    Physicists in the Laboratory for Attosecond Physics at Ludwig-Maximilians-Universitaet (LMU) in Munich and at the Max Planck Institute for Quantum Optics (MPQ) have developed a novel type of detector that enables the oscillation profile of light waves to be precisely determined.

    Light is hard to get a hold on. Light waves propagate with a velocity of almost 300,000 km per second, and the wavefront oscillates several hundred trillion times in that same interval. In the case of visible light, the physical distance between successive peaks of the light wave is less than 1 micrometer, and peaks are separated in time by less than 3 millionths of a billionth of a second (< 3 femtoseconds). To work with light, one must control it—and that requires precise knowledge of its behaviour. It may even be necessary to know the exact position of the crests or valleys of the light wave at a given instant. Researchers based at the Laboratory for Attosecond Physics (LAP) at the LMU Munich and the Max Planck Institute for Quantum Optics are now in a position to measure the exact location of such peaks within single ultrashort pulses of infrared light with the aid of a newly developed detector.

    Such pulses, which encompass only a few oscillations of the wave, can be used to investigate the behaviour of molecules and their constituent atoms, and the new detector is a very valuable tool in this context. Ultrashort laser pulses allow scientists to study dynamic processes at molecular and even subatomic levels. Using trains of these pulses, it is possible first to excite the target particles and then to film their responses in real time. In intense light fields, however, it is crucial to know the precise waveform of the pulses. Since the peak of the oscillating (carrier) light field and that of the pulse envelope can shift with respect to each other between different laser pulses, it is important to know the precise waveform of each pulse.

    The team at LAP, which was led by Dr. Boris Bergues and Professor Matthias Kling, head of the Ultrafast Imaging and Nanophotonics Group, has now made a decisive breakthrough in the characterization of light waves. Their new detector allows them to determine the 'phase," i.e. the precise positions of the peaks of the few oscillation cycles within each and every pulse, at repetition rates of 10,000 pulses per second. To do so, the group generated circularly polarized laser pulses in which the orientation of the propagating optical field rotates like a clock hand, and then focused the rotating pulse in ambient air.

    The interaction between the pulse and molecules in the air results in a short burst of electric current, whose direction depends on the position of the peak of the light wave. By analyzing the exact direction of the current pulse, the researchers were able to retrieve the phase of the 'carrier-envelope offset," and thus reconstruct the form of the light wave. Unlike the method conventionally employed for phase determination, which requires the use of a complex vacuum apparatus, the new technique works in ambient air and the measurements require very few extra components. "The simplicity of the setup is likely to ensure that it will become a standard tool in laser technology," explains Matthias Kling.

    “We believe that this technique can also be applied to lasers with much higher repetition rates and in different spectral regions”; says Boris Bergues.”Our methodology is of particular interest in the context of the characterization of extremely short laser pulses with high repetition rates, such as those generated at Europe’s Extreme Light Infrastructure (ELI)” adds Prof. Matthias Kling. When applied to the latest sources of ultrashort laser pulses, this new method of waveform analysis could pave the way to technological breakthroughs, as well as permitting new insights into the behaviour of elementary particles & in the fast lane.

    Science paper:
    Single-shot carrier–envelope-phase measurement in ambient air
    Optica

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
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    Research at the Max Planck Institute of Quantum Optics
    Light can behave as an electromagnetic wave or a shower of particles that have no mass, called photons, depending on the conditions under which it is studied or used. Matter, on the other hand, is composed of particles, but it can actually exhibit wave-like properties, giving rise to many astonishing phenomena in the microcosm.

    At our institute we explore the interaction of light and quantum systems, exploiting the two extreme regimes of the wave-particle duality of light and matter. On the one hand we handle light at the single photon level where wave-interference phenomena differ from those of intense light beams. On the other hand, when cooling ensembles of massive particles down to extremely low temperatures we suddenly observe phenomena that go back to their wave-like nature. Furthermore, when dealing with ultrashort and highly intense light pulses comprising trillions of photons we can completely neglect the particle properties of light. We take advantage of the large force that the rapidly oscillating electromagnetic field exerts on electrons to steer their motion within molecules or accelerate them to relativistic energies.

     
  • richardmitnick 9:37 am on December 19, 2019 Permalink | Reply
    Tags: "Ultrashort x-ray technique will probe conditions found at the heart of planets", , , , , , , Laser Technology, ,   

    From Imperial College London and STFC: “Ultrashort x-ray technique will probe conditions found at the heart of planets” 


    From Science and Technology Facilities Council

    and

    Imperial College London
    From Imperial College London

    19 December 2019
    Hayley Dunning

    1
    Working with the Gemini Laser. Credit: STFC

    Combining powerful lasers and bright x-rays, Imperial and STFC researchers have demonstrated a technique that will allow new extreme experiments.

    The new technique would be able to use a single x-ray flash to capture information about extremely dense and hot matter, such as can be found inside gas giant planets or on the crusts of dead stars.

    The same conditions are also found in fusion experiments, which are trying to create a new source of energy that mimics the Sun.

    ______________________________________
    We will now be able to probe warm dense matter much more efficiently and in unprecedented resolution.
    Dr Brendan Kettle
    ______________________________________

    The technique, reported this week in Physical Review Letters, was developed by a team led by Imperial College London scientists working with colleagues including those at the UK’s Central Laser Facility at the Science and Technology Facilities Council (STFC) Rutherford Appleton Laboratory [below], and was funded by the European Research Council.

    The researchers wanted to improve ways to study ‘warm dense matter’ – matter that has the same density as a solid, but is heated up to 10,000?C. Researchers can create warm dense matter in the lab, recreating the conditions in the hearts of planets or crucial for fusion power, but it is difficult to study.

    Accelerating discoveries

    The team used the Gemini Laser, which has two beams – one which can create the conditions for warm dense matter, and one which can create ultrashort and bright x-rays to probe the conditions inside the warm dense matter.

    2
    STFC Gemini Laser

    Previous attempts using lower-powered lasers required 50-100 x-ray flashes to get the same information that the new technique can gain in just one flash. The flashes last only femtoseconds (quadrillionths of a second), meaning the new technique can reveal what is happening within warm dense matter across very short timescales.

    First author Dr Brendan Kettle, from the Department of Physics at Imperial, said: “We will now be able to probe warm dense matter much more efficiently and in unprecedented resolution, which could accelerate discoveries in fusion experiments and astrophysics, such as the internal structure and evolution of planets including the Earth itself.”

    The technique could also be used to probe fast-changing conditions inside new kinds of batteries and memory storage devices.

    Answering key questions

    In the new study, the team used their technique to examine a heated sample of titanium, successfully showing that it could measure the distribution of electrons and ions.

    Lead researcher Dr Stuart Mangles, from the Department of Physics at Imperial, said: “We are planning to use the technique to answer key questions about how the electrons and ions in this warm dense matter ‘talk’ to each other, and how quickly can energy transfer from the electrons to the ions.”

    The Central Laser Facility’s Gemini Laser is currently one of the few places the right conditions for the technique can be created, but as new facilities start operating around the world, the team hope the technique can be expanded and used to do a whole new class of experiments.

    Dr Rajeev Pattathil, Gemini Group Leader at the Central Laser Facility, said: “With ultrashort x-ray flashes we can get a freeze-frame focus on transient or dynamic processes in materials, revealing key new fundamental information about materials here and in the wider Universe, and especially those in extreme states.”

    See the full article here .


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    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

    STFC-Science and Technology Facilities Council

    STFC Hartree Centre

    STFC Rutherford Appleton Laboratory at Harwell in Oxfordshire, UK

    Helping build a globally competitive, knowledge-based UK economy

    We are a world-leading multi-disciplinary science organisation, and our goal is to deliver economic, societal, scientific and international benefits to the UK and its people – and more broadly to the world. Our strength comes from our distinct but interrelated functions:

    Universities: we support university-based research, innovation and skills development in astronomy, particle physics, nuclear physics, and space science
    Scientific Facilities: we provide access to world-leading, large-scale facilities across a range of physical and life sciences, enabling research, innovation and skills training in these areas
    National Campuses: we work with partners to build National Science and Innovation Campuses based around our National Laboratories to promote academic and industrial collaboration and translation of our research to market through direct interaction with industry
    Inspiring and Involving: we help ensure a future pipeline of skilled and enthusiastic young people by using the excitement of our sciences to encourage wider take-up of STEM subjects in school and future life (science, technology, engineering and mathematics)

    We support an academic community of around 1,700 in particle physics, nuclear physics, and astronomy including space science, who work at more than 50 universities and research institutes in the UK, Europe, Japan and the United States, including a rolling cohort of more than 900 PhD students.

    STFC-funded universities produce physics postgraduates with outstanding high-end scientific, analytic and technical skills who on graduation enjoy almost full employment. Roughly half of our PhD students continue in research, sustaining national capability and creating the bedrock of the UK’s scientific excellence. The remainder – much valued for their numerical, problem solving and project management skills – choose equally important industrial, commercial or government careers.

    Our large-scale scientific facilities in the UK and Europe are used by more than 3,500 users each year, carrying out more than 2,000 experiments and generating around 900 publications. The facilities provide a range of research techniques using neutrons, muons, lasers and x-rays, and high performance computing and complex analysis of large data sets.

     
  • richardmitnick 12:51 pm on December 18, 2019 Permalink | Reply
    Tags: "Remote Quantum Systems Produce Interfering Photons", , , , Laser Technology, , , , ,   

    From Joint Quantum Institute: “Remote Quantum Systems Produce Interfering Photons” 

    JQI bloc

    From Joint Quantum Institute

    December 17, 2019

    Research Contact
    Steve Rolston
    rolston@umd.edu

    Story by Jillian Kunze

    1
    A schematic showing the paths taken by photons from two different sources in neighboring buildings. (Credit: S. Kelley/NIST)

    Scientists at the Joint Quantum Institute (JQI) have observed, for the first time, interference between particles of light created using a trapped ion and a collection of neutral atoms. Their results could be an essential step toward the realization of a distributed network of quantum computers capable of processing information in novel ways.

    In the new experiment, atoms in neighboring buildings produced photons—the quantum particles of light—in two distinct ways. Several hundred feet of optical cables then brought the photons together, and the research team, which included scientists from JQI as well as the Army Research Lab, measured a telltale interference pattern. It was the first time that photons from these two particular quantum systems were manipulated into having the same wavelength, energy and polarization—a feat that made the particles indistinguishable. The result, which may prove vital for communicating over quantum networks of the future, was published recently in the journal Physical Review Letters.

    “If we want to build a quantum internet, we need to be able to connect nodes of different types and functions,” says JQI Fellow Steve Rolston, a co-author of the paper and a professor of physics at the University of Maryland. “Quantum interference between photons generated by the different systems is necessary to eventually entangle the nodes, making the network truly quantum.”

    The first source of photons was a single trapped ion—an atom that is missing an electron—held in place by electric fields. Collections of these ions, trapped in a chain, are leading candidates for the construction of quantum computers due to their long lifetimes and ease of control. The second source of photons was a collection of very cold atoms, still in possession of all their electrons. These uncharged, or neutral, atomic ensembles are excellent interfaces between light and matter, as they easily convert photons into atomic excitations and vice versa. The photons produced by each of these two systems are typically different, limiting their ability to work together.

    In one building, researchers used a laser to excite a trapped barium ion to a higher energy. When it transitioned back to a lower energy, it emitted a photon at a known wavelength but in a random direction. When scientists captured a photon, they stretched its wavelength to match photons from the other source.

    In an adjacent building, a cloud of tens of thousands of neutral rubidium atoms generated the photons. Lasers were again used to pump up the energy of these atoms, and that procedure imprinted a single excitation across the whole cloud through a phenomenon called the Rydberg blockade. When the excitation shed its energy as photons, they traveled in a well-defined direction, making it easy for researchers to collect them.

    The team used an interferometer to measure the degree to which two photons were identical. A single photon entering the interferometer is equally likely to take either of two possible exits. And two distinguishable photons entering the interferometer at the same time don’t notice each other, acting like two independent single photons.

    But when researchers brought together the photons from their two sources, they almost always took the same exit—a result of quantum interference and an indication that they were nearly identical. This was precisely what the research team had hoped for: the first demonstration of interference between photons from these two very different quantum systems.

    In this experiment, photons traveled from the first building to the second via hundreds of feet of optical fiber. Due to this distance, sending photons from both systems to meet at the interferometer simultaneously was a feat of precise timing. Detectors were placed at the exits of the interferometer to detect where the photons came out, but the team often had to wait—gathering all the data took 24 hours over a period of 3 days.

    Further experimental upgrades could be used to generate a special quantum connection called entanglement between the ion and the neutral atoms. In entanglement, two quantum objects become so closely linked that the results from measuring one are correlated with the results from measuring the other, even if the objects are separated by a huge distance. Entanglement is necessary for the speedy algorithms that scientists hope to run on quantum computers in the future.

    Generating entanglement between different quantum systems usually requires identical photons, which the researchers were able to create. Unfortunately, trapped ions emit photons in a random direction, making the probability of catching them low. This meant that only about eight photons from the trapped ion made it to the interferometer each second. If the researchers attempted to perform more intricate experiments with that rate, the data could take months to collect. However, future work may increase how frequently the ion emits photons and allow for a useful rate of entanglement production.

    “This is a stepping-stone on the way to being able to entangle these two systems,” says Alexander Craddock, a graduate student at JQI and the lead author of this study. “And that would be fantastic, because you can then take advantage of all the different weird and wonderful properties of both of them.”

    In addition to Rolston and Craddock, co-authors of the paper include JQI graduate students John Hannegan, Dalia Ornelas-Huerta, and Andrew Hachtel, JQI postdoctoral researcher James Siverns, Army Research Laboratory scientists and JQI Affiliates Elizabeth Goldschmidt (now an Assistant Professor of Physics at the University of Illinois) and Qudsia Quraishi, and JQI Fellow Trey Porto.

    See the full article here .


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    JQI supported by Gordon and Betty Moore Foundation

    We are on the verge of a new technological revolution as the strange and unique properties of quantum physics become relevant and exploitable in the context of information science and technology.

    The Joint Quantum Institute (JQI) is pursuing that goal through the work of leading quantum scientists from the Department of Physics of the University of Maryland (UMD), the National Institute of Standards and Technology (NIST) and the Laboratory for Physical Sciences (LPS). Each institution brings to JQI major experimental and theoretical research programs that are dedicated to the goals of controlling and exploiting quantum systems.

     
  • richardmitnick 9:34 am on December 12, 2019 Permalink | Reply
    Tags: Laser Technology, , ,   

    From University of British Columbia: “New laser technique images quantum world in a trillionth of a second” 

    U British Columbia bloc

    From University of British Columbia


    MengXing Na and Andrea Damascelli at UBC’s Stewart Blusson Quantum Matter Institute (SBQMI). Credit: Research2Reality

    Dec 10, 2019
    Sachi Wickramasinghe
    UBC Media Relations
    Tel: 604-822-4636
    sachi.wickramasinghe@ubc.ca

    For the first time, researchers have been able to record, frame-by-frame, how an electron interacts with certain atomic vibrations in a solid. The technique captures a process that commonly causes electrical resistance in materials while, in others, can cause the exact opposite—the absence of resistance, or superconductivity.

    “The way electrons interact with each other and their microscopic environment determines the properties of all solids,” said MengXing Na, a University of British Columbia PhD student and co-lead author of the study, published last week in Science. “Once we identify the dominant microscopic interactions that define a material’s properties, we can find ways to ‘turn up’ or ‘down’ the interaction to elicit useful electronic properties.”

    Controlling these interactions is important for the technological exploitation of quantum materials, including superconductors, which are used in MRI machines, high-speed magnetic levitation trains, and could one day revolutionize how energy is transported.

    At tiny scales, atoms in all solids vibrate constantly. Collisions between an electron and an atom can be seen as a ‘scattering’ event between the electron and the vibration, called a phonon. The scattering can cause the electron to change both its direction and its energy. Such electron-phonon interactions lie at the heart of many exotic phases of matter, where materials display unique properties.

    2
    Ultrafast pulses of extreme ultraviolet light are created in a gas jet (white plasma), and are visible as blue dots on a phosphor screen as well as yellow beams from oxygen fluorescence. Credit: Research2Reality

    With the support of the Gordon and Betty Moore Foundation, the team at UBC’s Stewart Blusson Quantum Matter Institute (SBQMI) developed a new extreme-ultraviolet laser source to enable a technique called time-resolved photoemission spectroscopy for visualizing electron scattering processes at ultrafast timescales.

    “Using an ultrashort laser pulse, we excited individual electrons away from their usual equilibrium environment,” said Na. “Using a second laser pulse as an effective camera shutter, we captured how the electrons scatter with surrounding atoms on timescales faster than a trillionth of a second. Owing to the very high sensitivity of our setup, we were able to measure directly—for the first time—how the excited electrons interacted with a specific atomic vibration, or phonon.”

    The researchers performed the experiment on graphite, a crystalline form of carbon and the parent compound of carbon nanotubes, Bucky balls and graphene. Carbon-based electronics is a growing industry, and the scattering processes that contribute to electrical resistance may limit their application in nanoelectronics.

    The approach leverages a unique laser facility conceived by David Jones and Andrea Damascelli, and developed by co-lead author Arthur Mills, at the UBC-Moore Centre for Ultrafast Quantum Matter. The study was also supported by theoretical collaborations with the groups of Thomas Devereaux at Stanford University and Alexander Kemper at North Carolina State University.

    “Thanks to recent advances in pulsed-laser sources, we’re only just beginning to visualize the dynamic properties of quantum materials,” said Jones, a professor with UBC’s SBQMI and department of Physics and Astronomy.

    “By applying these pioneering techniques, we’re now poised to reveal the elusive mystery of high-temperature superconductivity and many other fascinating phenomena of quantum matter,” said Damascelli, scientific director of SBQMI.

    The work was supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative, the Natural Sciences and Engineering Research Council, Canada Foundation for Innovation, the B.C. Knowledge Development Fund, and the Canada First Research Excellence Fund.

    See the full article here .

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    U British Columbia Campus

    The University of British Columbia is a global centre for research and teaching, consistently ranked among the 40 best universities in the world. Since 1915, UBC’s West Coast spirit has embraced innovation and challenged the status quo. Its entrepreneurial perspective encourages students, staff and faculty to challenge convention, lead discovery and explore new ways of learning. At UBC, bold thinking is given a place to develop into ideas that can change the world.

     
  • richardmitnick 9:25 am on December 9, 2019 Permalink | Reply
    Tags: , , Laser Technology, Robert Byer,   

    From Stanford University: “Stanford physicist recalls life-changing first glimpse of a laser” 

    Stanford University Name
    From Stanford University

    November 19, 2019 [Just now in social media]
    Ker Than

    1
    Robert Byer has spent his career studying lasers after first seeing one at age 22. (Image credit: Misha Bruk)

    Physicist Robert Byer worked on lasers when they were still just an interesting technology, never imagining their myriad modern uses or how they would affect his life.

    Robert Byer was 22 years old when he first saw the light that changed his life.

    2
    Robert Byer developed the first visible, tunable red laser by routing a green laser through a nonlinear crystal (Image credit: Misha Bruk)

    One summer morning in 1964, Byer drove the hour from Berkeley down to Mountain View for a job interview at a California company called Spectra Physics. He walked in to find an empty lobby but could hear clapping and cheering in the back of the building. After politely waiting for several minutes, he followed the commotion to a darkened room filled with men whose jubilant faces were illuminated by a rod of red-orange light that seemed to float above an instrument-strewn table.

    Byer, who is now professor of applied physics and photon science at Stanford’s School of Humanities and Sciences, had walked in on history. The assembled physicists and engineers had just switched on the first ionized-gas laser that could be seen with the naked eye and they were basking in the glow of their accomplishment. Other visible-light lasers existed at the time, but they were weak and dim by comparison.

    Lasers – tuned, or “coherent,” light waves that can be focused into tight beams and adjusted to specific colors – had been invented a few years earlier, but Byer had never laid eyes on one until that moment. He always imagined they would resemble the beam of a strong flashlight. But the mercury ion laser he glimpsed that day, with its preternatural brightness and steady radiance, had a heft and a presence unlike any light Byer had ever seen.

    Roughly an inch thick and about two feet long, the laser also sparkled, glimmering like wet sand on a sunny day. Byer later learned that this speckled effect is a calling card of lasers, created when the crests and troughs of closely packed light waves crash into one another, creating interference.

    That captivating light, and the palpable excitement of the scientists Byer met that day, altered the course of his life. Recently graduated from UC Berkeley, he was slated to be married in a few months and already had a job lined up in Pasadena in Southern California. But those plans were now in doubt because Byer accepted a position at Spectra Physics that very day.

    Byer is slim, with neatly combed gray hair, a gentle, gravelly voice and keen eyes. He is logical and exacting when it comes to his work, but with regard to that momentous decision he made in his twenties, he says it just felt right. “All I had was a gut feeling,” he said. “I know there’s an expectation for scientists to take the rationality that’s in science and apply it to their personal relations, but that’s not what happens.”

    Byer called his fiancé a few days later and delicately asked if she would consider transferring from UCLA to UC Berkeley to finish her undergraduate studies. “Not on your life,” she said.

    Evi Guzsella did eventually agree, however, and Byer became the 13th employee at Spectra Physics. To make it up to her, Byer saved his earnings for a year and took his new wife on a two-month long European camping tour.

    _______________________________________________

    “In life, you make thousands of decisions, and almost always, the decisions that really matter, the ones that really count, are the ones you have the least information about.”

    —Robert Byer

    Professor of Applied Physics and of Photon Science
    _______________________________________________

    3
    Robert Byer uses an infrared viewing device to check the alignment of a near-IR laser through a linear crystal. (Image credit: Misha Bruk)

    Lasers are ubiquitous today. Modern society could not function without them. Lasers enable self-driving cars to sense their environments and surgeons to correct vision. A typical smartphone contains hundreds of them. The world’s digital and internet communications require the conversion of relatively short-range cellular and Wi-Fi signals into laser pulses that must be pushed through fiber optic cables to distant cell towers and web servers.

    But when Byer began working on lasers in 1964, they were so new that a use for them hadn’t been invented yet. The first widespread application of lasers was to speed up grocery checkout by using a red helium-neon laser to scan unique barcodes on products. The technology behind barcode checkout was developed as part of a joint project between the National Cash Register Corporation and Spectra Physics.

    By then, Byer had already left the company to enroll as a graduate student at Stanford University, studying under professor Stephen Harris to develop lasers with different colors and properties. For his thesis, Byer developed the first visible, tunable red laser by routing a green laser through a nonlinear crystal.

    Byer also helped develop the quietest, most stable laser in the world, called the diode-pumped YAG laser. YAG lasers are today found in everything from communications satellites to green handheld laser pointers, which Byer co-developed with two of his graduate students and cites as one of his favorite inventions (he had joined Stanford in 1969). YAG lasers also form the main beams of the gravitational wave-detecting instrument, LIGO, which in 2015 achieved the most precise measurement ever made by humans when its antenna detected the tenuous spacetime fluctuations generated by two colliding black holes 1.3 billion light-years away.

    The Spectra Physics laser that enchanted Byer 55 years ago sits in a clear case just outside his office, the bulky instrument an occasional reminder for Byer of how far the field – and he himself – have come.

    “In life, you make thousands of decisions, and almost always, the decisions that really matter, the ones that really count, are the ones you have the least information about,” Byer said. “We didn’t know as we worked to develop lasers where they would lead. They shaped the future only after they happened.”

    See the full article here .


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    Stanford University campus. No image credit

    Stanford University

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

    Stanford University Seal

     
  • richardmitnick 5:24 pm on December 6, 2019 Permalink | Reply
    Tags: "Gamma-ray laser moves a step closer to reality", , Laser Technology,   

    From UC Riverside: “Gamma-ray laser moves a step closer to reality” 

    UC Riverside bloc

    From UC Riverside

    December 5, 2019
    Iqbal Pittalwala

    1

    A physicist at the University of California, Riverside, has performed calculations showing hollow spherical bubbles filled with a gas of positronium atoms are stable in liquid helium.

    The calculations take scientists a step closer to realizing a gamma-ray laser, which may have applications in medical imaging, spacecraft propulsion, and cancer treatment.

    Extremely short-lived and only briefly stable, positronium is a hydrogen-like atom and a mixture of matter and antimatter — specifically, bound states of electrons and their antiparticles called positrons. To create a gamma-ray laser beam, positronium needs to be in a state called a Bose-Einstein condensate — a collection of positronium atoms in the same quantum state, allowing for more interactions and gamma radiation. Such a condensate is the key ingredient of a gamma-ray laser.

    “My calculations show that a bubble in liquid helium containing a million atoms of positronium would have a number density six times that of ordinary air and would exist as a matter-antimatter Bose-Einstein condensate,” said Allen Mills, a professor in the Department of Physics and Astronomy and sole author of the study that appears today in Physical Review A.

    Helium, the second-most abundant element in the universe, exists in liquid form only at extremely low temperatures. Mills explained helium has a negative affinity for positronium; bubbles form in liquid helium because helium repels positronium. Positronium’s long lifetime in liquid helium was first reported in 1957.

    When an electron meets a positron, their mutual annihilation could be one outcome, accompanied by the production of a powerful and energetic type of electromagnetic radiation called gamma radiation. A second outcome is the formation of positronium.

    Mills, who directs the Positron Laboratory at UC Riverside, said the lab is configuring an antimatter beam in a quest to produce the exotic bubbles in liquid helium that Mills’ calculations predict. Such bubbles could serve as a source of positronium Bose-Einstein condensates.

    “Near term results of our experiments could be the observation of positronium tunneling through a graphene sheet, which is impervious to all ordinary matter atoms, including helium, as well as the formation of a positronium atom laser beam with possible quantum computing applications,” Mills said.

    The research was supported by the National Science Foundation.

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
  • richardmitnick 3:45 pm on December 5, 2019 Permalink | Reply
    Tags: , , , , , Laser Technology, , , , Quantum vacuum squeezer   

    From MIT News: “New instrument extends LIGO’s reach” 

    MIT News

    From MIT News

    December 5, 2019
    Jennifer Chu

    1
    Researchers install a new quantum squeezing device into one of LIGO’s gravitational wave detectors. Image: Lisa Barsotti

    2
    A close-up of the quantum squeezer which has expanded LIGO’s expected detection range by 50 percent. Image: Maggie Tse

    Just a year ago, the National Science Foundation-funded Laser Interferometer Gravitational-wave Observatory, or LIGO, was picking up whispers of gravitational waves every month or so. Now, a new addition to the system is enabling the instruments to detect these ripples in space-time nearly every week.

    Since the start of LIGO’s third operating run in April, a new instrument known as a quantum vacuum squeezer has helped scientists pick out dozens of gravitational wave signals, including one that appears to have been generated by a binary neutron star — the explosive merging of two neutron stars.

    The squeezer, as scientists call it, was designed, built, and integrated with LIGO’s detectors by MIT researchers, along with collaborators from Caltech and the Australian National University, who detail its workings in a paper published today in the journal Physical Review Letters.

    What the instrument “squeezes” is quantum noise — infinitesimally small fluctuations in the vacuum of space that make it into the detectors. The signals that LIGO detects are so tiny that these quantum, otherwise minor fluctuations can have a contaminating effect, potentially muddying or completely masking incoming signals of gravitational waves.

    “Where quantum mechanics comes in relates to the fact that LIGO’s laser is made of photons,” explains lead author Maggie Tse, a graduate student at MIT. “Instead of a continuous stream of laser light, if you look close enough it’s actually a noisy parade of individual photons, each under the influence of vacuum fluctuations. Whereas a continuous stream of light would create a constant hum in the detector, the individual photons each arrive at the detector with a little ‘pop.’”

    “This quantum noise is like a popcorn crackle in the background that creeps into our interferometer, and is very difficult to measure,” adds Nergis Mavalvala, the Marble Professor of Astrophysics and associate head of the Department of Physics at MIT.

    With the new squeezer technology, LIGO has shaved down this confounding quantum crackle, extending the detectors’ range by 15 percent. Combined with an increase in LIGO’s laser power, this means the detectors can pick out a gravitational wave generated by a source in the universe out to about 140 megaparsecs, or more than 400 million light years away. This extended range has enabled LIGO to detect gravitational waves on an almost weekly basis.

    “When the rate of detection goes up, not only do we understand more about the sources we know, because we have more to study, but our potential for discovering unknown things comes in,” says Mavalvala, a longtime member of the LIGO scientific team. “We’re casting a broader net.”

    The new paper’s lead authors are graduate students Maggie Tse and Haocun Yu, and Lisa Barsotti, a principal research scientist at MIT’s Kavli Institute for Astrophysics and Space Research, along with others in the LIGO Scientific Collaboration.

    Quantum limit

    LIGO comprises two identical detectors, one located at Hanford, Washington, and the other at Livingston, Louisiana. Each detector consists of two 4-kilometer-long tunnels, or arms, each extending out from the other in the shape of an “L.”

    MIT /Caltech Advanced aLigo

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

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

    To detect a gravitational wave, scientists send a laser beam from the corner of the L-shaped detector, down each arm, at the end of which is suspended a mirror. Each laser bounces off its respective mirror and travels back down each arm to where it started. If a gravitational wave passes through the detector, it should shift one or both of the mirrors’ position, which would in turn affect the timing of each laser’s arrival back at its origin. This timing is something scientists can measure to identify a gravitational wave signal.

    The main source of uncertainty in LIGO’s measurements comes from quantum noise in a laser’s surrounding vacuum. While a vacuum is typically thought of as a nothingness, or emptiness in space, physicists understand it as a state in which subatomic particles (in this case, photons) are being constantly created and destroyed, appearing then disappearing so quickly they are extremely difficult to detect. Both the time of arrival (phase) and number (amplitude) of these photons are equally unknown, and equally uncertain, making it difficult for scientists to pick out gravitational-wave signals from the resulting background of quantum noise.

    And yet, this quantum crackle is constant, and as LIGO seeks to detect farther, fainter signals, this quantum noise has become more of a limiting factor.

    “The measurement we’re making is so sensitive that the quantum vacuum matters,” Barsotti notes.

    Putting the squeeze on “spooky” noise

    The research team at MIT began over 15 years ago to design a device to squeeze down the uncertainty in quantum noise, to reveal fainter and more distant gravitational wave signals that would otherwise be buried the quantum noise.

    Quantum squeezing was a theory that was first proposed in the 1980s, the general idea being that quantum vacuum noise can be represented as a sphere of uncertainty along two main axes: phase and amplitude. If this sphere were squeezed, like a stress ball, in a way that constricted the sphere along the amplitude axis, this would in effect shrink the uncertainty in the amplitude state of a vacuum (the squeezed part of the stress ball), while increasing the uncertainty in the phase state (stress ball’s displaced, distended portion). Since it is predominantly the phase uncertainty that contributes noise to LIGO, shrinking it could make the detector more sensitive to astrophysical signals.

    When the theory was first proposed nearly 40 years ago, a handful of research groups tried to build quantum squeezing instruments in the lab.

    “After these first demonstrations, it went quiet,” Mavalvala says.

    “The challenge with building squeezers is that the squeezed vacuum state is very fragile and delicate,” Tse adds. “Getting the squeezed ball, in one piece, from where it is generated to where it is measured is surprisingly hard. Any misstep, and the ball can bounce right back to its unsqueezed state.”

    Then, around 2002, just as LIGO’s detectors first started searching for gravitational waves, researchers at MIT began thinking about quantum squeezing as a way to reduce the noise that could possibly mask an incredibly faint gravitational wave signal. They developed a preliminary design for a vacuum squeezer, which they tested in 2010 at LIGO’s Hanford site. The result was encouraging: The instrument managed to boost LIGO’s signal-to-noise ratio — the strength of a promising signal versus the background noise.

    Since then, the team, led by Tse and Barsotti, has refined its design, and built and integrated squeezers into both LIGO detectors. The heart of the squeezer is an optical parametric oscillator, or OPO — a bowtie-shaped device that holds a small crystal within a configuration of mirrors. When the researchers direct a laser beam to the crystal, the crystal’s atoms facilitate interactions between the laser and the quantum vacuum in a way that rearranges their properties of phase versus amplitude, creating a new, “squeezed” vacuum that then continues down each of the detector’s arm as it normally would. This squeezed vacuum has smaller phase fluctuations than an ordinary vacuum, allowing scientists to better detect gravitational waves.

    In addition to increasing LIGO’s ability to detect gravitational waves, the new quantum squeezer may also help scientists better extract information about the sources that produce these waves.

    “We have this spooky quantum vacuum that we can manipulate without actually violating the laws of nature, and we can then make an improved measurement,” Mavalvala says. “It tells us that we can do an end-run around nature sometimes. Not always, but sometimes.”

    This research was supported, in part, by the National Science Foundation. LIGO was constructed by Caltech and MIT.

    See the full article here .


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    Please help promote STEM in your local schools.


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    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 1:57 pm on December 3, 2019 Permalink | Reply
    Tags: "When laser beams meet plasma- New data addresses gap in fusion research", , , Laser Technology, ,   

    From University of Rochester: “When laser beams meet plasma- New data addresses gap in fusion research” 


    From University of Rochester

    December 2, 2019
    Lindsey Valich
    lvalich@ur.rochester.edu

    1
    Researchers used the Omega Laser Facility at the Rochester’s Laboratory for Laser Energetics to make highly detailed measurements of laser-heated plasmas. (University photo / J. Adam Fenster)

    New research from the University of Rochester will enhance the accuracy of computer models used in simulations of laser-driven implosions. The research, published in the journal Nature Physics, addresses one of the challenges in scientists’ longstanding quest to achieve fusion.

    In laser-driven inertial confinement fusion (ICF) experiments, such as the experiments conducted at the University of Rochester’s Laboratory for Laser Energetics (LLE), short beams consisting of intense pulses of light—pulses lasting mere billionths of a second—deliver energy to heat and compress a target of hydrogen fuel cells. Ideally, this process would release more energy than was used to heat the system.

    Laser-driven ICF experiments require that many laser beams propagate through a plasma—a hot soup of free moving electrons and ions—to deposit their radiation energy precisely at their intended target. But, as the beams do so, they interact with the plasma in ways that can complicate the intended result.

    “ICF necessarily generates environments in which many laser beams overlap in a hot plasma surrounding the target, and it has been recognized for many years that the laser beams can interact and exchange energy,” says David Turnbull, an LLE scientist and the first author of the paper.

    To accurately model this interaction, scientists need to know exactly how the energy from the laser beam interacts with the plasma. While researchers have offered theories about the ways in which laser beams alter a plasma, none has ever before been demonstrated experimentally.

    Now, researchers at the LLE, along with their colleagues at Lawrence Livermore National Laboratory in California and the Centre National de la Recherche Scientifique in France, have directly demonstrated for the first time how laser beams modify the conditions of the underlying plasma, in turn affecting the transfer of energy in fusion experiments.

    “The results are a great demonstration of the innovation at the Laboratory and the importance of building a solid understanding of laser-plasma instabilities for the national fusion program,” says Michael Campbell, the director of the LLE.

    Using supercomputers to model fusion

    I asked U Rochester to tell me the supercomputers used in this work.
    Statement from U Rochester:

    “Hi Richard,
    This was experimental research that was conducted using the Omega laser facility at the University of Rochester’s Laboratory for Laser Energetics. The researchers used a novel high-power laser beam with a tunable wavelength to study the energy transfer between laser beams while simultaneously measuring the plasma conditions. This research was not conducted using supercomputers, but, rather, the experiments were designed to gather data that will be input into computer models to improve the predictive capabilities of models used in supercomputer simulations of inertial confinement fusion (ICF) experiments.”

    Researchers often use supercomputers to study the implosions involved in fusion experiments. It is important, therefore, that these computer models accurately depict the physical processes involved, including the exchange of energy from the laser beams to the plasma and eventually to the target.

    For the past decade, researchers have used computer models describing the mutual laser beam interaction involved in laser-driven fusion experiments. However, the models have generally assumed that the energy from the laser beams interacts in a type of equilibrium known as Maxwellian distribution—an equilibrium one would expect in the exchange when no lasers are present.

    “But, of course, lasers are present,” says Dustin Froula, a senior scientist at the LLE.

    Froula notes that scientists predicted almost 40 years ago that lasers alter the underlying plasma conditions in important ways. In 1980, a theory was presented that predicted these non-Maxwellian distribution functions in laser plasmas due to the preferential heating of slow electrons by the laser beams. In subsequent years, Rochester graduate Bedros Afeyan ’89 (PhD) predicted that the effect of these non-Maxwellian electron distribution functions would change how laser energy is transferred between beams.

    But lacking experimental evidence to verify that prediction, researchers did not account for it in their simulations.

    Turnbull, Froula, and physics and astronomy graduate student Avram Milder conducted experiments at the Omega Laser Facility at the LLE to make highly detailed measurements of the laser-heated plasmas. The results of these experiments show for the first time that the distribution of electron energies in a plasma is affected by their interaction with the laser radiation and can no longer be accurately described by prevailing models.

    The new research not only validates a longstanding theory, but it also shows that laser-plasma interaction strongly modifies the transfer of energy.

    “New inline models that better account for the underlying plasma conditions are currently under development, which should improve the predictive capability of integrated implosion simulations,” Turnbull says.

    This research is based upon work supported by the US Department of Energy National Nuclear Security Administration and the New York State Energy Research and Development Authority.

    See the full article here .

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    Please help promote STEM in your local schools.

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    U Rochester Campus

    The University of Rochester is one of the country’s top-tier research universities. Our 158 buildings house more than 200 academic majors, more than 2,000 faculty and instructional staff, and some 10,500 students—approximately half of whom are women.

    Learning at the University of Rochester is also on a very personal scale. Rochester remains one of the smallest and most collegiate among top research universities, with smaller classes, a low 10:1 student to teacher ratio, and increased interactions with faculty.

     
  • richardmitnick 11:08 am on November 20, 2019 Permalink | Reply
    Tags: "Gas Terahertz Laser is No Laughing Matter", Exploiting vibrational states, Laser Technology, , QCL-quantum cascade laser, Terahertz: Applications and limitations, The latest work uses a QCL as a pump rather than as the lasing medium itself., THz waves could be used for wireless communication., Using nitrous oxide the researchers showed that the gas lased.   

    From Optics & Photonics: “Gas Terahertz Laser is No Laughing Matter” 

    From Optics & Photonics

    18 November 2019
    Edwin Cartlidge

    1
    A laser the size of a shoebox produces THz waves (in green) by using a quantum cascade laser (red) to excite and rotate nitrous oxide molecules packed inside a 15cm-long cavity. [Image: Chad Scales, U.S. Army Futures Command]

    Scientists in the U.S. have dusted off and updated plans for a gas laser that can generate beams in the elusive terahertz (THz) frequency band. By pumping nitrous oxide (laughing gas) with a quantum cascade laser, they have shown it is possible to produce a broad spectrum of THz radiation using a compact device operating at room temperature [Science]

    Among the applications of such radiation, they say, are sensing, imaging and communication.

    Terahertz: Applications and limitations

    THz radiation sits in the electromagnetic spectrum between microwaves at lower frequencies and infrared waves above. The fact that it passes through many common materials, such as clothing, plastic and paper, while not having the energy to ionize and therefore harm living tissue, means it is potentially well-suited as a scanning technology. At the same time, its absorption by certain substances at well-defined frequencies suggests its use as a sensor of atmospheric gases.

    In addition, THz waves could be used for wireless communication. Not only could they accommodate higher bandwidths than lower-frequency radio waves, their relatively short range could also be exploited to prevent eavesdropping—with the amount of atmospheric absorption depending on the precise frequency used.

    Unfortunately, however, building suitable THz sources has proved difficult. There are a number of different technologies on the market—such as those that multiply harmonics of microwaves or mix the output of lasers—but each has its own limitations. None has a significant output around 1 THz, while many are bulky and expensive.

    In recent years, researchers have started to make THz sources from quantum cascade lasers (QCLs), whose alternating layers of high- and low-bandgap semiconductor create quantum wells that force electrons to emit a series of photons at specific wavelengths. Such lasers are chip-based, making them potentially small and cheap, but they need to be cooled, are inefficient and cover a limited frequency range.

    Exploiting vibrational states

    In contrast, the latest work uses a QCL as a pump, rather than as the lasing medium itself. The laser in this case consists of a gas of nitrous oxide, the molecules of which when pumped vibrate and then move into specific rotational states. Held in a suitable cavity, the molecules emit THz photons in the form of a laser beam when dropping back down from one rotational state to another.

    In previous decades, cavities several meters long were pumped by large carbon-dioxide lasers. Theoretical models predicted that if the cavity were too small, and the pressure of the gas too high, collisions between gas molecules would prevent the build-up of energy necessary for a population inversion.

    Henry Everitt of Duke University, NC, developed a model in the 1980s showing it should in fact be possible to build such compact molecular lasers. However, that model still involved a carbon-dioxide laser as the pump. It was only after working on the theory for a number of years, in collaboration with Steven Johnson and colleagues at the Massachusetts Institute of Technology, MA, he says, did it become clear that a QCL could also pack enough power to make the gas lase.

    The trick, according to Johnson, lay in considering vibrational states of the molecules that had been previously overlooked. By limiting energy dissipation when pressure in the cavity is high, he explains in a press release accompanying the research, those vibrations “sort of give you more breathing room to keep rotating and keep making THz waves.”

    Lasing with laughing gas

    Exploiting that insight, Everitt, who now works for the U.S. Army, teamed up with Federico Capasso and colleagues at Harvard University, MA. Capasso co-invented QCLs while at Bell Labs in the 1990s, and his group has now used an infrared QCL to pump a gas-filled copper tube just 15 centimeters long and 5 millimeters in diameter.

    Using nitrous oxide, the researchers showed that the gas lased. What’s more, they found that the frequency of that laser beam varied as they tuned the QCL. They were able to produce 37 lines, each with a width of just a few kilohertz, across the spectrum from 0.25 to 0.96 THz. They also used modeling to show that many other gases pumped in this way—each being paired to its own QCL—should produce laser lines spanning more than 1 THz.

    According to Capasso, the device outperforms all existing laser sources in this region of the spectrum—something, he adds, that could not have been predicted with any confidence when he and his colleagues embarked on the research. “It was not obvious that pumping with a broadly tunable mid-infrared QCL was the way to get broadband THz lasing in a gas,” he says.

    But Capasso notes that there are still hurdles to overcome before the technology can be commercialized and made ready for real-world applications. Among these, he says, are optimizing the cavity to boost power output as well as changing the gas to carbon monoxide in order to expand the laser’s range up a few THz.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Opticsand 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 11:26 am on November 10, 2019 Permalink | Reply
    Tags: , By watching how atoms behave when they’re suspended in midair rather than in free fall physicists have come up with a new way to measure Earth’s gravity., Laser Technology, Physicists split atoms into a weird quantum state called superposition — where one version of the atom is slightly higher than the other., , ,   

    From Science News: “Trapping atoms in a laser beam offers a new way to measure gravity” 

    From Science News

    November 7, 2019
    Maria Temming

    The technique can measure slight gravitational variations, which could help in mapping terrain.

    1
    A new type of experiment to measure the strength of gravity uses atoms suspended in laser light (with the machinery pictured above), rather than free-falling atoms. V. Xu.

    By watching how atoms behave when they’re suspended in midair, rather than in free fall, physicists have come up with a new way to measure Earth’s gravity.

    Traditionally, scientists have measured gravity’s influence on atoms by tracking how fast atoms tumble down tall chutes. Such experiments can help test Einstein’s theory of gravity and precisely measure fundamental constants (SN: 4/12/18). But the meters-long tubes used in free-fall experiments can be unwieldy and difficult to shield from environmental interference such as stray magnetic fields. With a new tabletop setup, physicists can gauge the strength of Earth’s gravity by monitoring atoms suspended a couple millimeters in the air by laser light.

    This redesign, described in the Nov. 8 Science, could better probe the gravitational forces exerted by small objects. The technique also could be used to measure slight gravitational variations at different places in the world, which may help in mapping the seafloor or finding oil and minerals underground (SN: 2/12/08).

    Physicist Victoria Xu and colleagues at the University of California, Berkeley began by launching a cloud of cesium atoms into the air and using flashes of light to split each atom into a superposition state. In this weird quantum limbo, each atom exists in two places at once: one version of the atom hovering a few micrometers higher than the other. Xu’s team then trapped these split cesium atoms in midair with light from a laser.

    3
    Got you, atom. To measure gravity, physicists split atoms into a weird quantum state called superposition — where one version of the atom is slightly higher than the other (blue dots connected by vertical yellow bands in this illustration). The researchers trap these atoms in midair using laser light (horizontal blue bands). While held in the light, each version of a single atom behaves slightly differently, due to their different positions in Earth’s gravitational field. Measuring those differences allows physicists to determine the strength of Earth’s gravity at that location.

    Measuring the strength of gravity with atoms that are held in place, rather than being tugged downward by a gravitational field, requires tapping into the atoms’ wave-particle duality (SN: 11/5/10). That quantum effect means that, much as light waves can act like particles called photons, atoms can act like waves. And for each cesium atom caught in superposition, the higher version of the atom wave undulates a little faster than its lower counterpart, due to the atoms’ slightly different positions in Earth’s gravitational field. By tracking how fast the waviness of the two versions of an atom gets out of sync, physicists can calculate the strength of Earth’s gravity at that spot.

    “Very impressive,” says physicist Alan Jamison of MIT. To him, one big promise of the new technique is more controlled measurements. “It’s quite a challenge to work on these drop experiments, where you have a 10-meter-long tower,” he says. “Magnetic fields are hard to shield, and the environment produces them all over the place — all the electrical systems in your building, and so forth. Working in a smaller volume makes it easier to avoid those environmental noises.”

    More compact equipment can also measure shorter-range gravity effects, says study coauthor Holger Müller. “Let’s say you don’t want to measure the gravity of the entire Earth, but you want to measure the gravity of a small thing, such as a marble,” he says. “We just need to put the marble close to our atoms [and hold it there]. In a traditional free-fall setup, the atoms would spend a very short time close to our marble — milliseconds — and we would get much less signal.”

    Physicist Kai Bongs of the University of Birmingham in England imagines using the new kind of atomic gravimeter to investigate the nature of dark matter or test a fundamental facet of Einstein’s theory of gravity called the equivalence principle (SN: 4/28/17). Many unified theories of physics proposed to reconcile quantum mechanics and Einstein’s theory of gravity — which are incompatible — violate the equivalence principle in some way. “So looking for violations might guide us to the grand unified theory,” he says. “That’s one of the Holy Grails in physics.”

    See the full article here .


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