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  • richardmitnick 12:39 pm on December 21, 2020 Permalink | Reply
    Tags: "When light and atoms share a common vibe", , , In the new study EPFL researchers managed to entangle the photon and the phonon (i.e. light and vibration) produced in the fission of an incoming laser photon inside the crystal., , , , , Quantum superposition   

    From École Polytechnique Fédérale de Lausanne (CH): “When light and atoms share a common vibe” 


    From École Polytechnique Fédérale de Lausanne (CH)

    Scientists from EPFL, MIT, and CEA Saclay demonstrate a state of vibration that exists simultaneously at two different times. They evidence this quantum superposition by measuring the strongest class of quantum correlations between light beams that interact with the vibration.


    When light and atoms share a common vibe.

    An especially counter-intuitive feature of quantum mechanics is that a single event can exist in a state of superposition – happening bothhereandthere, or bothtodayandtomorrow.

    Such superpositions are hard to create, as they are destroyed if any kind of information about the place and time of the event leaks into the surrounding – and even if nobody actually records this information. But when superpositions do occur, they lead to observations that are very different from that of classical physics, questioning down to our very understanding of space and time.

    Scientists from EPFL, MIT, and CEA Saclay, publishing in Science Advances, demonstrate a state of vibration that exists simultaneously at two different times, and evidence this quantum superposition by measuring the strongest class of quantum correlations between light beams that interact with the vibration.

    The researchers used a very short laser-pulse to trigger a specific pattern of vibration inside a diamond crystal. Each pair of neighboring atoms oscillated like two masses linked by a spring, and this oscillation was synchronous across the entire illuminated region. To conserve energy during this process, a light of a new color is emitted, shifted toward the red of the spectrum.

    This classical picture, however, is inconsistent with the experiments. Instead, both light and vibration should be described as particles, or quanta: light energy is quantized into discrete photons while vibrational energy is quantized into discrete phonons (named after the ancient Greek “photo = light” and “phono = sound”).

    The process described above should therefore be seen as the fission of an incoming photon from the laser into a pair of photon and phonon – akin to nuclear fission of an atom into two smaller pieces.

    But it is not the only shortcoming of classical physics. In quantum mechanics, particles can exist in a superposition state, like the famous Schrödinger cat being alive and dead at the same time.

    Even more counterintuitive: two particles can become entangled, losing their individuality. The only information that can be collected about them concerns their common correlations. Because both particles are described by a common state (the wavefunction), these correlations are stronger than what is possible in classical physics. It can be demonstrated by performing appropriate measurements on the two particles. If the results violate a classical limit, one can be sure they were entangled.

    In the new study, EPFL researchers managed to entangle the photon and the phonon (i.e., light and vibration) produced in the fission of an incoming laser photon inside the crystal. To do so, the scientists designed an experiment in which the photon-phonon pair could be created at two different instants. Classically, it would result in a situation where the pair is created at time t1 with 50% probability, or at a later time t2 with 50% probability.

    But here comes the “trick” played by the researchers to generate an entangled state. By a precise arrangement of the experiment, they ensured that not even the faintest trace of the light-vibration pair creation time (t1 vs. t2) was left in the universe. In other words, they erased information about t1 and t2. Quantum mechanics then predicts that the phonon-photon pair becomes entangled, and exists in a superposition of time t1andt2. This prediction was beautifully confirmed by the measurements, which yielded results incompatible with the classical probabilistic theory.

    By showing entanglement between light and vibration in a crystal that one could hold in their finger during the experiment, the new study creates a bridge between our daily experience and the fascinating realm of quantum mechanics.

    “Quantum technologies are heralded as the next technological revolution in computing, communication, sensing, says Christophe Galland, head of the Laboratory for Quantum and Nano-Optics at EPFL and one of the study’s main authors. “They are currently being developed by top universities and large companies worldwide, but the challenge is daunting. Such technologies rely on very fragile quantum effects surviving only at extremely cold temperatures or under high vacuum. Our study demonstrates that even a common material at ambient conditions can sustain the delicate quantum properties required for quantum technologies. There is a price to pay, though: the quantum correlations sustained by atomic vibrations in the crystal are lost after only 4 picoseconds — i.e., 0.000000000004 of a second! This short time scale is, however, also an opportunity for developing ultrafast quantum technologies. But much research lies ahead to transform our experiment into a useful device — a job for future quantum engineers.”

    See the full article here .

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    EPFL bloc

    EPFL campus

    EPFL (CH) is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 12:37 pm on December 8, 2020 Permalink | Reply
    Tags: , Entangled quantum systems, , , , , Quantum superposition, , Three of the four fundamental forces in physics can be described in terms of quantum theory. This is not the case for the fourth force (gravity).,   

    From University of Gronigen [Rijksuniversiteit Groningen] (NL) via phys.org: “Experiment to test quantum gravity just got a bit less complicated” 

    From University of Gronigen [Rijksuniversiteit Groningen] (NL)

    via


    phys.org

    December 8, 2020

    1
    In the proposed experiment, two diamonds are each placed in superposition and studied in freefall. Apart from gravity, the Casimir effect also draws them together, causing noise in the experiment. A thin copper plate can shield this effect, reducing the noise and making the experiment more manageable. Credit: A. Mazumdar, University of Groningen.

    Is gravity a quantum phenomenon? That has been one of the big outstanding questions in physics for decades. Together with colleagues from the UK, Anupam Mazumdar, a physicist from the University of Groningen, proposed an experiment that could settle the issue. However, it requires studying two very large entangled quantum systems in freefall. In a new paper
    [Physical Review A], which has a third-year Bachelor’s student as the first author, Mazumdar presents a way to reduce background noise to make this experiment more manageable.

    Three of the four fundamental forces in physics can be described in terms of quantum theory. This is not the case for the fourth force (gravity), which is described by Einstein’s theory of general relativity. The experiment that Mazumdar and his colleagues previously designed could prove or disprove the quantum nature of gravity.

    Superposition

    A well-known consequence of the quantum theory is the phenomenon called quantum superposition: in certain situations, quantum states can have two different values at the same time. Take an electron that is irradiated with laser light. Quantum theory says that it can either absorb or not absorb the photon energy from the light. Absorbing the energy would alter the electron’s spin, a magnetic moment that can be either up or down. The result of quantum superposition is that the spin is both up and down.

    These quantum effects take place in tiny objects, such as electrons. By targeting an electron in a specially constructed miniature diamond, it is possible to create superposition in a much larger object. The diamond is small enough to sustain this superposition, but also large enough to feel the pull of gravity. This characteristic is what the experiment exploits: placing two of these diamonds next to each other in freefall and, therefore, canceling out external gravity. This means that they only interact through the gravity between them.

    Challenging

    And that is where another quantum phenomenon comes in. Quantum entanglement means that when two or more particles are generated in close proximity, their quantum states are linked. In the case of the diamonds, if one is spin up, the other, entangled diamond should be spin down. So, the experiment is designed to determine whether quantum entanglement occurs in the pair during freefall, when the force of the gravity between the diamonds is the only way that they interact.

    “However, this experiment is very challenging,” explains Mazumdar. When two objects are very close together, another possible mechanism for interaction is present, the Casimir effect. In a vacuum, two objects can attract each other through this effect. “The size of the effect is relatively large and to overcome the noise it creates, we would have to use relatively large diamonds.” It was clear from the outset that this noise should be reduced to make the experiment more manageable. Therefore, Mazumdar wanted to know if shielding for the Casimir effect was possible.

    Lockdown

    He handed the problem to Thomas van de Kamp, a third-year Bachelor’s student of Physics. “He came to me because he was interested in quantum gravity and wanted to do a research project for his Bachelor’s thesis,” says Mazumdar. During the spring lockdown, when most normal classes were suspended, Van de Kamp started working on the problem. “Within a remarkably short time, he presented his solution, which is described in our paper.”

    This solution is based on placing a conducting plate of copper, around one millimeter thick, between the two diamonds. The plate shields the Casimir potential between them. Without the plate, this potential would draw the diamonds closer to each other. But with the plate, the diamonds are no longer attracted to each other, but to the plate between them. Mazumdar: “This removes the interaction between the diamonds through the Casimir effect, and therefore removes a lot of noise from the experiment.”

    Remarkable

    The calculations performed by Van de Kamp show that the masses of the two diamonds can be reduced by two orders of magnitude. “It may seem like a small step, but it does make the experiment less demanding.” Furthermore, other parameters such as the level of vacuum needed during the experiment also become less demanding due to the shielding of the Casimir effect. Mazumdar says that a further update on the experiment, which also includes a contribution from Bachelor’s student Thomas van de Kamp, will probably appear in the near future. “So, his six-month project has brought him co-authorship on two papers, quite a remarkable feat.”

    See the full article here.

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    The University of Gronigen [Rijksuniversiteit Groningen] (NL) is a public research university in the city of Groningen in the Netherlands. The university was founded in 1614 and is the second-oldest university in the Netherlands. In 2014, the university celebrated its 400th anniversary. Currently, RUG is placed in the top 100 universities worldwide according to three international ranking tables.

    The university was ranked 65th in the world, according to Academic Ranking of World Universities (ARWU) in 2019. In April 2013, according to the results of the International Student Barometer, the University of Groningen, for the third time in a row, was voted the best university of the Netherlands.

    The University of Groningen has eleven faculties, nine graduate schools, 27 research centres and institutes, and more than 175-degree programmes. The university’s alumni and faculty include Johann Bernoulli, Aletta Jacobs, four Nobel Prize winners, nine Spinoza Prize winners, one Stevin Prize winner, royalty, multiple mayors, the first president of the European Central Bank, and a secretary general of NATO.

     
  • richardmitnick 10:33 am on September 19, 2019 Permalink | Reply
    Tags: Classical nonseparability can be applied to acoustic waves not just light waves., From Light to Sound, , , Quantum superposition, ,   

    From University of Arizona: “Sound of the Future: A New Analog to Quantum Computing” 

    U Arizona bloc

    From University of Arizona

    Sept. 17, 2019
    Emily Dieckman

    University of Arizona engineers are using soundwaves to search through big data with more stability and ease.

    1
    Pierre Deymier (right) and UA President Robert C. Robbins examine the acoustic system that allowed researchers to create Bell states using phonons. (Photo: Paul Tumarkin/Tech Launch Arizona)

    Human beings create a lot of data in the digital age – whether it’s through everyday items like social media posts, emails and Google searches, or more complex information about health, finances and scientific findings.

    The International Data Corp. reported that the global datasphere contained 33 zettabytes, or 33 trillion gigabytes, in 2018. By 2025, they expect that number to grow to 175 zettabytes. 175 zettabytes of information stored on DVDs would fill enough DVDs to circle Earth 222 times.

    While quantum computing has been touted as a way to intelligently sort through big data, quantum environments are difficult to create and maintain. Entangled quantum bit states, or qubits, usually last less than a second before collapsing. Qubits are also highly sensitive to their surrounding environments and must be stored at cryogenic temperatures.

    In a paper Nature Communications Physics, researchers in the University of Arizona Department of Materials Science and Engineering have demonstrated the possibility for acoustic waves in a classical environment to do the work of quantum information processing without the time limitations and fragility.

    “We could run our system for years,” said Keith Runge, director of research in the Department of Materials Science and Engineering and one of the paper’s authors. “It’s so robust that we could take it outside to a tradeshow without it being perturbed at all – earlier this year, we did.”

    Materials science and engineering research assistant professor Arif Hasan led the research. Other co-authors include MSE research assistant professor Lazaro Calderin; undergraduate student Trevor Lata; Pierre Lucas, professor of MSE and optical sciences; and Pierre Deymier, MSE department head, member of the applied mathematics Graduate Interdisciplinary Program, and member of the BIO5 Institute. The team is working with Tech Launch Arizona, the office of the UA that commercializes inventions stemming from research, to patent their device and is investigating commercial pathways to bring the innovation to the public.

    Quantum Superposition

    In classical computing, information is stored as either 0s or 1s, the same way a coin must land on either heads or tails. In quantum computing, qubits can be stored in both states at the same time – a so-called superposition of states. Think of a coin balanced on its side, spinning so quickly that both heads and tails seem to appear at once.

    When qubits are entangled, anything that happens to one qubit affects the other through a principle called nonseparability. In other words, knock down one spinning coin on a table and another spinning coin on the same table falls down, too. A principle called nonlocality keeps the particles linked even if they’re far apart – knock down one spinning coin, and its entangled counterpart on the other side of the universe falls down, too. The entangled qubits create a Bell state, in which all parts of a collective are affected by one another.

    “This is key, because if you manipulate just one qubit, you are manipulating the entire collection of qubits,” Deymier said. “In a regular computer, you have many bits of info stored as 0s or 1s, and you have to address each one of them.”

    From Light to Sound

    But, like a coin spinning on its edge, quantum mechanics are fragile. The act of measuring a quantum state can cause the link to collapse, or decohere – just like how taking a picture of a spinning coin will mean capturing just one side of the coin. That’s why qubit states can only be maintained for short periods.

    But there’s a way around the use of quantum mechanics for data processing: Optical scientists and electrical and computer engineering researchers have demonstrated the ability to create systems of photons, or units of light, that exhibit nonseparability without nonlocality. Though nonlocality is important for specific applications like cryptography, it’s the nonseparability that matters for applications like quantum computing. And particles that are nonseparable in classical Bell states, rather than entangled in a quantum Bell state, are much more stable.

    The materials science and engineering team has taken this a step further by demonstrating for the first time that that classical nonseparability can be applied to acoustic waves, not just light waves. They use phi-bits, units made up of quasi-particles called phonons that transmit sound and heat waves.

    “Light lasers and single photons are part of the field photonics, but soundwaves fall under the umbrella of phononics, or the study of phonons,” Deymier said. “In addition to being stable, classically entangled acoustic waves are easy to interact with and manipulate.”

    Complex Science, Simple Tools

    The materials to demonstrate such a complex concept were simple, including three aluminum rods, enough epoxy to connect them and some rubber bands for elasticity.

    Researchers sent a wave of sound vibrations down the rods, then monitored two degrees of freedom of the waves: what direction the waves moved down the rods (forward or backward) and how the rods moved in relation to one another (whether they were waving in the same direction and at similar amplitudes). To excite the system into a nonseparable state, they identified a frequency at which these two degrees of freedom were linked and sent the waves at that frequency. The result? A Bell state.

    “So, we have an acoustic system that gives us the possibility creating these Bell states,” Deymier said. “It’s the complete analog to quantum mechanics.”

    Demonstrating that this is possible has opened the door to applying classical nonseparability to the emerging field of phononics. Next, the researchers will work to increase the number of degrees of freedom that can be classically entangled – the more, the better. They also want to develop algorithms that can use these nonseparable states to manipulate information.

    Once the system is refined, they plan to resize it from the tabletop down to the microscale, ready to deploy on computer chips in data centers around the world.

    This work was supported by the W.M. Keck Foundation and the National Science Foundation Emerging Frontiers in Research and Innovation Program.

    See the full article here .


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    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    U Arizona mirror lab-Where else in the world can you find an astronomical observatory mirror lab under a football stadium?

    University of Arizona’s Biosphere 2, located in the Sonoran desert. An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 8:59 am on July 30, 2019 Permalink | Reply
    Tags: A team of physicists at University of Illinois at Chicago and the University of Hamburg have taken a different approach., Entangled Majorana quasiparticles produced by splitting an electron into two halves are surprisingly stable., , , Majorana quasiparticles, , , Quantum superposition, , , , They remember how they've been moved around a property that could be exploited for storing information., They've started with a rhenium superconductor a material that conducts electricity with zero resistance when supercooled to around 6 Kelvin (–267°C; 449°F)., , ,   

    From University of Illinois and U Hamburg, via Science Alert: “An Elusive Particle That Acts as Its Own Antiparticle Has Just Been Imaged” 

    U Illinois bloc

    From University of Illinois Chicago

    and

    2
    U Hamburg

    via

    30 JULY 2019
    MICHELLE STARR

    3
    (Palacio-Morales et al. Science Advances, 2019)

    New images of the Majorana fermion have brought physicists a step closer to harnessing the mysterious objects for quantum computing.

    These strange objects – particles that acts as their own antiparticles – have a vast as-yet untapped potential to act as qubits, the quantum bits that are the basic units of information in a quantum computer.

    IBM iconic image of Quantum computer

    They’re equivalent to binary bits in a traditional computer. But, where regular bits can represent a 1 or a 0, qubits can be either 1, 0 or both at the same time, a state known as quantum superposition. Quantum superposition is actually pretty hard to maintain, although we’re getting better at it.

    This is where Majorana quasiparticles come in. These are excitations in the collective behaviour of electrons that act like Majorana fermions, and they have a number of properties that make them an attractive candidate for qubits.

    Normally, a particle and an antiparticle will annihilate each other, but entangled Majorana quasiparticles produced by splitting an electron into two halves are surprisingly stable. In addition, they remember how they’ve been moved around, a property that could be exploited for storing information.

    But the quasiparticles have to remain separated by a sufficient distance. This can be done with a special nanowire, but a team of physicists at the University of Illinois at Chicago and the University of Hamburg in Germany have taken a different approach.

    They’ve started with a rhenium superconductor, a material that conducts electricity with zero resistance when supercooled to around 6 Kelvin (–267°C; 449°F).

    On top of these superconductors, the researchers deposited nanoscale islands of single layers of magnetic iron atoms. This creates what is known as a topological superconductor – that is, a superconductor that contains a topological knot.

    “This topological knot is similar to the hole in a donut,” explained physicist Dirk Morr of the University of Illinois at Chicago.

    “You can deform the donut into a coffee mug without losing the hole, but if you want to destroy the hole, you have to do something pretty dramatic, such as eating the donut.”

    When electrons flow through the superconductor, the team predicted that Majorana fermions would appear in a one-dimensional mode at the edges of the iron islands – around the so-called donut hole. And that by using a scanning tunneling microscope – an instrument used for imaging surfaces at the atomic level – they would see this visualised as a bright line.

    Sure enough, a bright line showed up.

    It’s not the first time Majorana fermions have been imaged, but it does represent a step forward. And just last month, a different team of researchers revealed that they had been able to turn Majorana quasiparticles on and off.

    But being able to visualise these particles, the researchers said, brings us closer to using them as qubits.

    “The next step will be to figure out how we can quantum engineer these Majorana qubits on quantum chips and manipulate them to obtain an exponential increase in our computing power,” Morr said.

    The research has been published in Science Advances.

    See the full article here .

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    Please help promote STEM in your local schools.

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    4

    The University

    Universität Hamburg is the largest institution for research and education in northern Germany. As one of the country’s largest universities, we offer a diverse range of degree programs and excellent research opportunities. The University boasts numerous interdisciplinary projects in a broad range of fields and an extensive partner network of leading regional, national, and international higher education and research institutions.
    Sustainable science and scholarship

    Universität Hamburg is committed to sustainability. All our faculties have taken great strides towards sustainability in both research and teaching.
    Excellent research

    As part of the Excellence Strategy of the Federal and State Governments, Universität Hamburg has been granted clusters of excellence for 4 core research areas: Advanced Imaging of Matter (photon and nanosciences), Climate, Climatic Change, and Society (CliCCS) (climate research), Understanding Written Artefacts (manuscript research) and Quantum Universe (mathematics, particle physics, astrophysics, and cosmology).

    An equally important core research area is Infection Research, in which researchers investigate the structure, dynamics, and mechanisms of infection processes to promote the development of new treatment methods and therapies.
    Outstanding variety: over 170 degree programs

    Universität Hamburg offers approximately 170 degree programs within its eight faculties:

    Faculty of Law
    Faculty of Business, Economics and Social Sciences
    Faculty of Medicine
    Faculty of Education
    Faculty of Mathematics, Informatics and Natural Sciences
    Faculty of Psychology and Human Movement Science
    Faculty of Business Administration (Hamburg Business School).

    Universität Hamburg is also home to several museums and collections, such as the Zoological Museum, the Herbarium Hamburgense, the Geological-Paleontological Museum, the Loki Schmidt Garden, and the Hamburg Observatory.
    History

    Universität Hamburg was founded in 1919 by local citizens. Important founding figures include Senator Werner von Melle and the merchant Edmund Siemers. Nobel Prize winners such as the physicists Otto Stern, Wolfgang Pauli, and Isidor Rabi taught and researched at the University. Many other distinguished scholars, such as Ernst Cassirer, Erwin Panofsky, Aby Warburg, William Stern, Agathe Lasch, Magdalene Schoch, Emil Artin, Ralf Dahrendorf, and Carl Friedrich von Weizsäcker, also worked here.
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    U Illinois campus

    The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

    With our land-grant heritage as a foundation, we pioneer innovative research that tackles global problems and expands the human experience. Our transformative learning experiences, in and out of the classroom, are designed to produce alumni who desire to make a significant, societal impact.

    The University of Illinois at Chicago (UIC) is a public research university in Chicago, Illinois. Its campus is in the Near West Side community area, adjacent to the Chicago Loop. The second campus established under the University of Illinois system, UIC is also the largest university in the Chicago area, having approximately 30,000 students[9] enrolled in 15 colleges.

    UIC operates the largest medical school in the United States with research expenditures exceeding $412 million and consistently ranks in the top 50 U.S. institutions for research expenditures.[10][11][12] In the 2019 U.S. News & World Report’s ranking of colleges and universities, UIC ranked as the 129th best in the “national universities” category.[13] The 2015 Times Higher Education World University Rankings ranked UIC as the 18th best in the world among universities less than 50 years old.[14]

    UIC competes in NCAA Division I Horizon League as the UIC Flames in sports. The Credit Union 1 Arena (formerly UIC Pavilion) is the Flames’ venue for home games.

     
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