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  • richardmitnick 4:44 pm on June 14, 2018 Permalink | Reply
    Tags: , Entanglement on Demand, , , Quantum Mechanics, TU Delft   

    From The Kavli Foundation and TU Delft: “Delft Scientists Make First ‘On Demand’ Entanglement Link” 

    KavliFoundation

    From The Kavli Foundation

    and

    TU Delft

    June 13, 2018
    Contact details:
    Prof. dr. ir. Ronald Hanson
    QuTech, Delft University of Technology
    Lorentzweg 1, 2628 CJ Delft, Netherlands
    R.Hanson@tudelft.nl
    +31 15 27 86133

    Researchers at QuTech in Delft have succeeded in generating quantum entanglement between two quantum chips faster than the entanglement is lost. Entanglement – once referred to by Einstein as “spooky action” – forms the link that will provide a future quantum internet its power and fundamental security. Via a novel smart entanglement protocol and careful protection of the entanglement, the scientists led by Prof. Ronald Hanson are the first in the world to deliver such a quantum link ‘on demand’. This opens the door to connect multiple quantum nodes and create the very first quantum network in the world. They publish their results on 14 June in Nature.

    Quantum Internet

    By exploiting the power of quantum entanglement it is theoretically possible to build a quantum internet that cannot be eavesdropped on. However, the realization of such a quantum network is a real challenge: you have to be able to create entanglement reliably, ‘on demand’, and maintain it long enough to pass the entangled information to the next node. So far, this has been beyond the capabilities of quantum experiments.

    1
    Researchers from QuTech in Delft working on the ‘entanglement on demand’ experiment’. The pictures show prof. Ronald Hanson, dr. Peter Humphreys and dr. Norbert Kalb, all from the group of prof Ronald Hanson of Delft University.

    Scientists at QuTech in Delft have now been the first to experimentally generate entanglement over a distance of two metres in a fraction of a second, ‘on demand’, and subsequently maintain this entanglement long enough to enable -in theory- further entanglement to a third node. ‘The challenge is now to be the first to create a network of multiple entangled nodes: the first version of a quantum internet’, professor Hanson states.

    Higher performance

    In 2015, Ronald Hanson’s research group already became world news: they were the first to generate long-lived quantum entanglement over a distance (1.3 kilometres), , allowing them to providefull experimental proof of quantum entanglement for the first time. This experiment is the basis of their current approach to developing a quantum internet: distant single electrons on diamond chips are entangled using photons as mediators.

    However, so far this experiment has not had the necessary performance to create a real quantum network. Hanson: ‘In 2015 we managed to establish a connection once an hour, while the connection only remained active for a fraction of a second. It was impossible to add a third node, let alone multiple nodes, to the network.’

    Entanglement on demand

    The scientists have now made multiple innovative improvements to the experiment. First of all, they demonstrated a new entanglement method. This allows for the generation of entanglement forty times a second between electrons at a distance of two metres. Peter Humphreys, an author of the paper, emphasises: ‘This is a thousand times faster than with the old method.’ In combination with a smart way of protecting the quantum link from external noise, the experiment has now surpassed a crucial threshold: for the first time, entanglement can be created faster than it is lost.

    Through technical improvements, the experimental setup is now always ready for ‘entanglement-on-demand’. Hanson: ‘Just like in the current internet, we always want to be online, the system has to entangle on each request.’ The scientists have achieved this by adding smart quality checks. Humphreys: ‘These checks only take a fraction of the total experimental time, while allowing us to ensure that our system is ready for entanglement, without any manual action’.

    Networks

    The researchers already demonstrated last year that they were able to protect https://qutech.nl/one-step-closer-to-the-quantum-internet-by-distillation/a quantum entangled link while a new connection was generated. By combining this and their new results, they are ready to create quantum networks with more than two nodes. The Delft scientists now plan to realize such a network between several quantum nodes. Hanson: ‘In 2020, we want to connect four cities in the Netherlands via quantum entanglement. This will be the very first quantum internet in the world.’

    This work was supported by the Netherlands Organisation for Scientific Research (NWO) through a VICI grant and by the European Research Council through a Starting Grant and a Synergy Grant.

    See the full article here .


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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

    Delft University of Technology (Dutch: Technische Universiteit Delft) also known as TU Delft, is the largest and oldest Dutch public technological university, located in Delft, Netherlands. It counts as one of the best universities for engineering and technology worldwide, typically seen within the top 20.[7] It is repeatedly considered the best university of technology in the Netherlands.[8]

    With eight faculties and numerous research institutes,[9] it hosts over 19,000 students (undergraduate and postgraduate), more than 2,900 scientists, and more than 2,100 support and management staff.[5]

    The university was established on 8 January 1842 by William II of the Netherlands as a Royal Academy, with the main purpose of training civil servants for the Dutch East Indies. The school rapidly expanded its research and education curriculum, becoming first a Polytechnic School in 1864, Institute of Technology in 1905, gaining full university rights, and finally changing its name to Delft University of Technology in 1986.[1]

    Dutch Nobel laureates Jacobus Henricus van ‘t Hoff, Heike Kamerlingh Onnes, and Simon van der Meer have been associated with TU Delft. TU Delft is a member of several university federations including the IDEA League, CESAER, UNITECH International, and 3TU.

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  • richardmitnick 1:09 pm on April 26, 2018 Permalink | Reply
    Tags: , Quantum Mechanics, , Spooky quantum entanglement goes big in new experiments   

    From ScienceNews: “Spooky quantum entanglement goes big in new experiments” 


    ScienceNews

    1
    DRUMMING UP ENTANGLEMENT Two teams of scientists demonstrated quantum linkages between two specially designed jiggling structures: drumheadlike objects (illustrated) and silicon beams (not shown). Petja Hyttinen/Aalto University, Olli Hanhirova/ARKH Architects.

    Quantum entanglement has left the realm of the utterly minuscule, and crossed over to the just plain small. Two teams of researchers report that they have generated ethereal quantum linkages, or entanglement, between pairs of jiggling objects visible with a magnifying glass or even the naked eye — if you have keen vision.

    Physicist Mika Sillanpää and colleagues entangled the motion of two vibrating aluminum sheets, each 15 micrometers in diameter — a few times the thickness of spider silk. And physicist Sungkun Hong and colleagues performed a similar feat with 15-micrometer-long beams made of silicon, which expand and contract in width in a section of the beam. Both teams report their results in the April 26 Nature Stabilized entanglement of massive mechanical oscillators and Remote quantum entanglement between two micromechanical oscillators.

    “It’s a first demonstration of entanglement over these artificial mechanical systems,” says Hong, of the University of Vienna. Previously, scientists had entangled vibrations in two diamonds that were macroscopic, meaning they were visible (or nearly visible) to the naked eye. But this is the first time entanglement has been seen in macroscopic structures constructed by humans, which can be designed to meet particular technological requirements.

    Entanglement is a strange feature of quantum mechanics, through which two objects’ properties become intertwined. Measuring the properties of one object immediately reveals the state of the other, even though the duo may be separated by a large distance (SN: 8/5/17, p. 14).

    Quantum mechanics’ weird rules typically apply to small fry — atoms, electrons and other tiny particles — and not to larger things such as cats, chairs or buildings. But that division leads to a confounding puzzle. “Atoms behave like atoms, and cats behave like cats, and so where is that transition in between?” says physicist Ben Sussman of the National Research Council of Canada in Ottawa, who was not involved in the research.

    Now, scientists are extending the dividing line to larger and larger objects. “One of our motivations is to keep on testing how far we can push quantum mechanics,” says Sillanpää, of Aalto University in Finland. “There might be some fundamental limit for how big objects can be” and still be quantum.

    In Sillanpää’s experiment, two tiny aluminum sheets — consisting of about a trillion atoms and just barely visible with the naked eye — vibrate like drumheads and interact with microwaves bouncing back and forth in a cavity. Those microwaves play the role of drum major, causing the two drumheads to sync up their motions. In many previous demonstrations of entanglement, the delicate quantum link is transient. But this one was long-lived, persisting as long as half an hour in experiments, Sillanpää says, and, in theory, even longer. “Our entanglement lasts forever, basically.”

    ____________________________________________________________
    In unison

    Physicists have entangled the motions of pairs of wiggling structures. Seen in these electron microscope images are the different types of devices that two teams used: vibrating drumheadlike objects (one at left) and expanding and contracting silicon beams (similar to that shown at right).

    4
    Mika Sillanpää/Aalto University, R. Riedinger et al/Nature 2016
    ____________________________________________________________

    Taking a different tactic, Hong and colleagues demonstrated entanglement with two silicon beams, big enough to be seen with a magnifying glass. Within a region of each beam, in a 1-micrometer-long section composed of about 10 billion atoms, the structure expanded and contracted — as if taking deep breaths in and out — in response to being hit with light. Instead of microwaves, Hong and colleagues’ work used infrared light of the wavelength typically transmitted in telecommunications networks made of optical fibers, which means it could be incorporated into a future quantum internet. “From a technology standpoint, that really is crucial,” says physicist John Teufel of the National Institute of Standards and Technology in Boulder, Colo., who was not involved with the work.

    Scientists could use such vibrating structures within a quantum network to convert quantum information from one type to another, transitioning from particles of light to vibrations, for example. Once constructed, a quantum internet could allow quantum computers to communicate and provide unhackable communication across the globe (SN: 10/15/16, p. 13).

    The ability to entangle these specially designed structures moves scientists a step closer to that vision. “You can really start to think about building real devices with these things,” Sussman says.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

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  • richardmitnick 2:16 pm on April 20, 2018 Permalink | Reply
    Tags: , , , Quantum Mechanics, Tracking Entanglement in a Quantum Simulator   

    From Optics & Photonics: “Tracking Entanglement in a Quantum Simulator” 

    Optics & Photonics

    4.19.18
    Stewart Wills

    1
    In an experiment involving a linear array of ions, the IQOQI Innsbruck team tracked the evolution of entanglement as the system evolved in time. [Image: IQOQI Innsbruck/Harald Ritsch]

    Using a system of 20 trapped calcium ions, physicists in Austria have demonstrated what they describe as the largest register of entangled, individually controllable quantum bits (qubits) shown to date [Phys. Rev. X]. The team was able both to encode a complex initial state in the 20-ion ensemble and to demonstrate entanglement among those individual qubits at various stages of the system’s evolution. Moreover, by using both analytical and numerical “entanglement witnesses” developed in the work, the team found that it could detect not only entanglement among pairs of neighboring ions, but “genuine multipartite entanglement” among neighboring groups of three, four and even five ions.

    The result, according to Ben Lanyon, a co-leader of the research at the Institute of Quantum Optics and Quantum Information (IQOQI), Innsbruck, provides evidence that ion-based quantum simulators—which some view as a way station on the road to full-fledged quantum computers—do indeed provide a window into otherwise inscrutable quantum behavior. “We’re building confidence,” he says, “that we are accessing complex quantum states” in these simulators.

    Toward individual control

    Quantum simulators use systems of atoms, ions or other qubits to model quantum behavior beyond the abilities of classical computing algorithms. They’ve come a long way in the past year, with several groups successfully building simulators involving 50 or more qubits. But Lanyon says these experiments with larger ensembles haven’t yet demonstrated the level of control of each individual particle in the system, and of particle entanglement, shown in the 20-qubit Innsbruck experiments.

    To achieve that control, the IQOQI team employed a radio-frequency Paul trap to set up a register of 20 calcium ions in a linear array. Next, the researchers used laser fields to flip every second qubit, setting up a specific initial Hamiltonian, or energy state, for the system. They then quenched the system at various time steps, and used quantum-state-dependent resonance fluorescence imaging, via a single-ion-resolving CCD camera, to measure the state of each qubit.

    2
    In the experiment, the Austrian group (a) captured an array of 20 ions in Paul trap, (b and c) used laser fields to initialize the ions, (d) allowed the system to evolve in time to an unknown quantum state, and then (e and f) quenched the evolution and used resonance fluorescence imaging to read out the quantum state of each qubit. [Image: N. Friis et al., “Observation of entangled states of a fully controlled 20-qubit system,” Phys. Rev. X, doi: 10.1103/PhysRevX.8.021012 (link is above)]

    From twins to quintuplets

    The IQOQI team next dug into measuring the level of entanglement among the qubits. Estimating the full quantum state density matrix for the 20-qubit ensemble would have required assessing billions of measurement bases. So the researchers focused on the set of bases required to reconstruct the density matrices of all neighboring 3-quibit groups in the linear array—a much more tractable problem involving only 27 bases.

    Using those density matrices, and a parameter called the genuine multipartite negativity, they were able to establish that all adjacent pairs of the linear array became entangled very quickly as the system evolved. But what about multipartite entanglement, among larger numbers of qubits? To assess that, Lanyon and his co-lead investigator, Rainer Blatt, turned for help to two groups of theorists, Marcus Huber’s team at IQOQI’s Vienna branch, and Martin Plenio’s research group at the University of Ulm, Germany.

    The theoretical groups devised two complementary entanglement witnesses that could be used to establish higher orders of entanglement. Huber’s group offered a relatively simple, analytical method that was effective at inferring entangled triplets from the two-qubit observables already established by the Innsbruck team. For detecting multipartite entanglement among collections of four and five qubits, Plenio’s team provided a computationally intense, “brute force” numerical search technique.

    Putting all of the techniques together, the Innsbruck team was able to establish that adjacent pairs of particles in the linear system quickly became entangled, and that quantum correlations built up among triplets, most quadruplets and some quintuplets as the system evolved in time.

    Accessing true quantum behavior

    Establishing multipartite entanglement for groups of more than five qubits outstripped the computational power that the team could bring to bear, and “remains an open challenge,” according to the paper. But even that five-qubit limit, according to Lanyon, might be a feature rather than a bug, since it underscores that the simulator is indeed demonstrating quantum behavior beyond the reach of classical algorithms.

    “What we’re interested in doing with these controlled quantum simulators is accessing quantum dynamics that we can’t otherwise access using conventional means,” says Lanyon. “So we’re kind of encouraged that we’re seeing this behavior—that our simulator goes beyond the point where we can follow it with existing methods at the moment.” As simulator systems become larger and larger, he maintains, it’s important to have methods to verify that the simulator is “behaving the way we think it is”; verifying lower-order entanglement is one way to “get feedback in the lab that we’re doing the right thing.”

    Meanwhile, Lanyon notes that while the techniques don’t scale well in order of entanglement, they do scale efficiently in system size. That opens up the prospect for practical simulators involving hundreds or even thousands of particles. And the paper concludes that the ability to individually control qubit–qubit interactions means that the system “has the capability to perform universal quantum simulation and quantum computation.”

    See the full article here .

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    Optics & 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 2:34 pm on April 14, 2018 Permalink | Reply
    Tags: , , Laser 'tweezers', Quantum Mechanics,   

    From Harvard via Science Alert: “Scientists Just Achieved The World’s Most Precise Chemical Reaction” 

    Harvard University
    Harvard University

    Science Alert

    13 APR 2018
    MIKE MCRAE

    1
    (johnason/istock)

    Scientists have just performed the world’s most precisely controlled chemical reaction, sticking together just two atoms from elements that wouldn’t normally form a molecule.

    The two elements – sodium and caesium – produced an interesting alloy-like molecule. On top of that, this method of creation could set the way of making just the kind of materials we might need in future technology.

    A team of Harvard University scientists used laser ‘tweezers’ to manipulate individual atoms of the two alkali metals into close proximity, and provided a photon to help them bond into a single molecule.

    Chemical reactions are usually hit-and-miss affairs, where vast numbers of atoms are thrown together under the right conditions, and probability does the rest.

    This ‘stochastic’ method of chemical reactions is all well and good if the combination of elements are a decent match. But when scientists want a really exotic pairing, they need to get creative.

    Sodium (Na) and caesium (Cs) are both found in the same group on the periodic table – as you may remember from high school chemistry, it means they tend to have similar reactive properties.

    Periodic table Sept 2017. Wikipedia

    They also don’t tend to bump into each other and easily bond as a molecule.

    Which is really a shame – the polarised electrical properties of a molecule of NaCs would make it super useful for storing quantum ‘qubit’ states of superposition that can also interact easily with other components.

    This all-in-one combination of qubit storage plus interaction is something desperately needed in future technology.

    “The direction of quantum information processing is one of the things we’re excited about,” says lead researcher and chemist Kang-Kuen Ni.

    Improbable doesn’t mean impossible, though: if these two atoms happen to be close enough with the right energy, a connection can form.

    To achieve this perfect mix of energy and timing, the researchers held single atoms in overlapping magneto-optical traps and pelted them with photons to cool them down to a fraction of a degree above absolute zero.

    Meanwhile, they used a pair of lasers tuned to create an electrical effect, causing each atom to move towards each laser’s focus, as if they were pulled into two sci-fi tractor beams.

    Nearby, the two atoms can collide easily. This still doesn’t necessarily guarantee they’ll bond, given the need to conserve the right momentum and energy levels.

    It’s a tricky juggle of conditions, one the researchers managed using the right laser pulses.

    The end result is a brief flicker of a bond between two atoms in the same quantum state, providing the researchers with details on what’s happening on an extremely fine level.

    Ni says the next step would be to create longer lasting molecules by combining them while in a ground state, rather than an excited one.

    “I think that a lot of scientists will follow, now that we have shown what is possible,” says Ni.

    The ultimate goal would be to tailor the creation of far more complex molecules, making use not only of their classical shapes but creating tiny quantum components for the next generation of computing.

    And for this kind of construction, nothing can be left to sheer chance.

    “The experimental demonstration represents for the first time that a chemical reaction process is deterministically controlled,” Jun Ye of the US National Institute of Standards and Technology told David Bradley from Chemistryworld.

    Though Ye wasn’t part of the study, he expressed excitement over the results.

    “Control of molecular interactions, including reaction, at the most fundamental level has been a long-standing goal in physical science.”

    This research was published in Science.

    See the full article here .

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    Harvard University campus
    Harvard is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

     
  • richardmitnick 2:01 pm on April 14, 2018 Permalink | Reply
    Tags: Entanglement of Time, Quantum Mechanics,   

    From Science Alert: “If You Thought Quantum Mechanics Was Weird, Check Out Entangled Time” 

    ScienceAlert

    Science Alert

    14 APR 2018
    ELISE CRULL

    1
    (bestdesigns/iStock)

    Where the future influences the past.

    In the summer of 1935, the physicists Albert Einstein and Erwin Schrödinger engaged in a rich, multifaceted and sometimes fretful correspondence about the implications of the new theory of quantum mechanics.

    The focus of their worry was what Schrödinger later dubbed entanglement: the inability to describe two quantum systems or particles independently, after they have interacted.

    Until his death, Einstein remained convinced that entanglement showed how quantum mechanics was incomplete. Schrödinger thought that entanglement was the defining feature of the new physics, but this didn’t mean that he accepted it lightly.

    “I know of course how the hocus pocus works mathematically,” he wrote to Einstein on 13 July 1935. “But I do not like such a theory.”

    Schrödinger’s famous cat, suspended between life and death, first appeared in these letters, a byproduct of the struggle to articulate what bothered the pair.

    The problem is that entanglement violates how the world ought to work. Information can’t travel faster than the speed of light, for one.

    But in a 1935 paper [Physical Review Journals Archive], Einstein and his co-authors showed how entanglement leads to what’s now called quantum nonlocality, the eerie link that appears to exist between entangled particles.

    If two quantum systems meet and then separate, even across a distance of thousands of lightyears, it becomes impossible to measure the features of one system (such as its position, momentum and polarity) without instantly steering the other into a corresponding state.

    Up to today, most experiments have tested entanglement over spatial gaps.

    The assumption is that the ‘nonlocal’ part of quantum nonlocality refers to the entanglement of properties across space. But what if entanglement also occurs across time? Is there such a thing as temporal nonlocality?

    The answer, as it turns out, is yes.

    Just when you thought quantum mechanics couldn’t get any weirder, a team of physicists at the Hebrew University of Jerusalem reported in 2013 that they had successfully entangled photons that never coexisted.

    Previous experiments involving a technique called ‘entanglement swapping’ had already showed quantum correlations across time, by delaying the measurement of one of the coexisting entangled particles; but Eli Megidish and his collaborators were the first to show entanglement between photons whose lifespans did not overlap at all.

    Here’s how they did it.

    First, they created an entangled pair of photons, ‘1-2’ (step I in the diagram below). Soon after, they measured the polarisation of photon 1 (a property describing the direction of light’s oscillation) – thus ‘killing’ it (step II).

    1
    (Provided)

    Photon 2 was sent on a wild goose chase while a new entangled pair, ‘3-4’, was created (step III). Photon 3 was then measured along with the itinerant photon 2 in such a way that the entanglement relation was ‘swapped’ from the old pairs (‘1-2’ and ‘3-4’) onto the new ‘2-3’ combo (step IV).

    Some time later (step V), the polarisation of the lone survivor, photon 4, is measured, and the results are compared with those of the long-dead photon 1 (back at step II).

    The upshot? The data revealed the existence of quantum correlations between ‘temporally nonlocal’ photons 1 and 4. That is, entanglement can occur across two quantum systems that never coexisted.

    What on Earth can this mean? Prima facie, it seems as troubling as saying that the polarity of starlight in the far-distant past – say, greater than twice Earth’s lifetime – nevertheless influenced the polarity of starlight falling through your amateur telescope this winter.

    Even more bizarrely: maybe it implies that the measurements carried out by your eye upon starlight falling through your telescope this winter somehow dictated the polarity of photons more than 9 billion years old.

    Lest this scenario strike you as too outlandish, Megidish and his colleagues can’t resist speculating on possible and rather spooky interpretations of their results.

    Perhaps the measurement of photon 1’s polarisation at step II somehow steers the future polarisation of 4, or the measurement of photon 4’s polarisation at step V somehow rewrites the past polarisation state of photon 1.

    In both forward and backward directions, quantum correlations span the causal void between the death of one photon and the birth of the other.

    Just a spoonful of relativity helps the spookiness go down, though.

    In developing his theory of special relativity, Einstein deposed the concept of simultaneity from its Newtonian pedestal.

    As a consequence, simultaneity went from being an absolute property to being a relative one. There is no single timekeeper for the Universe; precisely when something is occurring depends on your precise location relative to what you are observing, known as your frame of reference.

    So the key to avoiding strange causal behaviour (steering the future or rewriting the past) in instances of temporal separation is to accept that calling events ‘simultaneous’ carries little metaphysical weight.

    It is only a frame-specific property, a choice among many alternative but equally viable ones – a matter of convention, or record-keeping.

    The lesson carries over directly to both spatial and temporal quantum nonlocality.

    Mysteries regarding entangled pairs of particles amount to disagreements about labelling, brought about by relativity.

    Einstein showed that no sequence of events can be metaphysically privileged – can be considered more real – than any other. Only by accepting this insight can one make headway on such quantum puzzles.

    The various frames of reference in the Hebrew University experiment (the lab’s frame, photon 1’s frame, photon 4’s frame, and so on) have their own ‘historians’, so to speak.

    While these historians will disagree about how things went down, not one of them can claim a corner on truth. A different sequence of events unfolds within each one, according to that spatiotemporal point of view.

    Clearly, then, any attempt at assigning frame-specific properties generally, or tying general properties to one particular frame, will cause disputes among the historians.

    But here’s the thing: while there might be legitimate disagreement about which properties should be assigned to which particles and when, there shouldn’t be disagreement about the very existence of these properties, particles, and events.

    These findings drive yet another wedge between our beloved classical intuitions and the empirical realities of quantum mechanics.

    As was true for Schrödinger and his contemporaries, scientific progress is going to involve investigating the limitations of certain metaphysical views.

    Schrödinger’s cat, half-alive and half-dead, was created to illustrate how the entanglement of systems leads to macroscopic phenomena that defy our usual understanding of the relations between objects and their properties: an organism such as a cat is either dead or alive. No middle ground there.

    Most contemporary philosophical accounts of the relationship between objects and their properties embrace entanglement solely from the perspective of spatial nonlocality.

    But there’s still significant work to be done on incorporating temporal nonlocality – not only in object-property discussions, but also in debates over material composition (such as the relation between a lump of clay and the statue it forms), and part-whole relations (such as how a hand relates to a limb, or a limb to a person).

    For example, the ‘puzzle’ of how parts fit with an overall whole presumes clear-cut spatial boundaries among underlying components, yet spatial nonlocality cautions against this view. Temporal nonlocality further complicates this picture: how does one describe an entity whose constituent parts are not even coexistent?

    Discerning the nature of entanglement might at times be an uncomfortable project. It’s not clear what substantive metaphysics might emerge from scrutiny of fascinating new research by the likes of Megidish and other physicists.

    In a letter to Einstein, Schrödinger notes wryly (and deploying an odd metaphor): “One has the feeling that it is precisely the most important statements of the new theory that can really be squeezed into these Spanish boots – but only with difficulty.”

    We cannot afford to ignore spatial or temporal nonlocality in future metaphysics: whether or not the boots fit, we’ll have to wear ’em.

    See the full article here .

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  • richardmitnick 8:01 am on March 28, 2018 Permalink | Reply
    Tags: , , , EPFL invests in quantum science and technology, EPFL’s Institute of Physics, , , Quantum Mechanics   

    From École Polytechnique Fédérale de Lausanne EPFL: “EPFL invests in quantum science and technology” 

    EPFL bloc

    École Polytechnique Fédérale de Lausanne EPFL

    28.03.18
    Nik Papageorgiou

    1
    The IBM Q Experience running on a tablet at IBM Research. (credit: Connie Zhou for IBM).

    Having identified Quantum Science and Technology as a strategic research area to be developed and reinforced, EPFL’s Institute of Physics is plunging headlong into the field with two new research openings, a master’s course, and partnering with IBM and their cutting-edge quantum-computer platform.

    It seems that the future will involve disruptive technologies that rely on the “spooky world” of quantum mechanics. Harnessing the properties of the quantum world, the world is preparing to usher in technologies that seem to be the stuff of science fiction, such as light-based quantum communications, unbreakable quantum cryptography, and quantum computers that run a million times faster than today’s fastest supercomputers.

    Europe is already heavily invested in what has come to be abbreviated as “QST” – Quantum Science and Technology, with its FET Flagship on Quantum Technologies, while Switzerland runs its own, federally funded NCCR-QSIT project.

    Now, EPFL’s Institute of Physics (IPHYS) is reinforcing its own QST efforts, specifically in theoretical quantum science. The Institute recently made an open call for a faculty position in QST, with the selection committee now planning interviews to select one of the short-listed candidates in April. “A second call in QST is very high on our priority list,” says director of IPHYS Professor Harald Brune. “We will be proposing it as soon as possible.”

    In addition to its efforts in QST research, EPFL’s teaching in QST enjoys high visibility. Dr Marc-André Dupertuis, a researcher with two IPHYS labs, has been running a Master course in quantum optics and quantum information since 2013. The course came to life through the efforts of Dupertuis and his assistant Clément Javerzac-Galy, and represents a major commitment by EPFL to establish itself as a leader in the future of QST.

    This view is apparently shared by IBM, an industry pioneer in the field. In 2016, the tech giant launched “the IBM Quantum Experience (QX)”, a cloud-based platform on which students and researchers can learn, research, and interact with a real quantum computer housed in an IBM Research lab through a simple Internet connection and a browser. In 2017, IBM chose EPFL alongside MIT and the University of Waterloo to be one of the first institutions in the world to use its quantum computer for teaching.

    As part of the QST teaching initiative, IBM made the QX platform available to Master students taking Dupertuis’ course. “We are using the IBM Q Experience in the framework of our quantum information class,” says Clément Javerzac-Galy. “It’s fascinating for the students to be the first generation to use a quantum machine and it’s a tremendous tool to speed up the learning curve in quantum information. Things you could previously only theorize about, you can now practice on a real machine.”

    Recognizing EPFL’s effort in QST teaching, IBM also marked the event with a lengthy tweet. “This shows that EPFL is already a top institution in the world for what concerns teaching in this domain,” says Harald Brune. Today, the QX community spans nearly 80,000 users running 3 million quantum experiments and more than 35 third-party research publications, while users can compete for three different awards.

    “This year we will be in the privileged to be able to calculate with 20 quantum bits as opposed to 5 last year,” says Marc-André Dupertuis. “Plus, this year the QX community expects to pass the ‘Quantum supremacy’ limit of quantum computing. A quantum computer will have obtained for the first time at least one result that would have been unthinkable to calculate with any existing conventional supercomputer.”

    See the full article here .

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    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university with students, professors and staff from over 120 nations. A dynamic environment, open to Switzerland and the world, EPFL is centered on its three missions: teaching, research and technology transfer. EPFL works together with an extensive network of partners including other universities and institutes of technology, developing and emerging countries, secondary schools and colleges, industry and economy, political circles and the general public, to bring about real impact for society.

     
  • richardmitnick 9:23 pm on March 19, 2018 Permalink | Reply
    Tags: , , , , , , Gravastar model, Quantum Mechanics,   

    From Sky & Telescope: “Physicist Proposes Alternative to Black Holes” 

    SKY&Telescope bloc

    Sky & Telescope

    March 19, 2018
    Ben Skuse

    A physicist has incorporated a quantum mechanical idea with general relativity to arrive at a new alternative to black hole singularities.

    1
    An artist’s rendering of Cygnus X-1, an X-ray-emitting black hole that formed when a large star caved in. (We see its X-rays now as it feeds from its stellar companion.) But are black holes the inevitable next step after neutron stars? NASA / CXC / M.Weiss.

    What do you get when you cross two hypothetical alternatives to black holes? A self-consistent semiclassical relativistic star, according to Raúl Carballo-Rubio (International School for Advanced Studies, Trieste, Italy) whose recently published results in the February 6th Physical Review Letters describe a new mathematical model for the fate of massive stars.

    When a massive star comes to the end of its life, it goes supernova, leaving behind a dense core that — according to conventional thought — continues to collapse to form either a neutron star or black hole. To which fate a particular star is destined comes down to its mass. Neutron stars find a balance between the repulsive force of quantum mechanical degeneracy pressure and the attractive force of gravity, while more massive cores collapse into black holes, unable to fight the overwhelming pull of their own gravity.

    Repulsive Gravity

    Now, Carballo-Rubio adds an extra force into the mix: quantum fluctuations. Quantum mechanics has shown that virtual particles spontaneously pop into and out of existence — the effects can be measured best in a vacuum, but these fluctuations can happen anywhere in spacetime. These particles can be thought of as fluctuations of positive and negative energy that under normal conditions would cancel out. But the extreme gravity of compact objects breaks this balance, effectively generating negative energy. This negative energy creates a repulsive gravitational force.

    “The existence of quantum [fluctuations] due to gravitational fields has been known since the late 1970s,” explains Carballo-Rubio. But physicists didn’t know how to take this effect into account in collapsing stars.

    Carballo-Rubio derived equations that combine general relativity and quantum mechanics in a way that accounts for quantum fluctuations. Moreover, he found solutions that balance attractive and negative gravity for stellar masses that would otherwise have produced black holes. Dubbing them “semiclassical relativistic stars,” these compact objects do not fully collapse under their own weight to form an event horizon, and are therefore not black holes.

    Hybrid Star

    Interestingly, Carballo-Rubio’s semiclassical relativistic stars bear hallmarks of previously proposed black hole alternatives: gravastars and black stars.

    Gravastars and black stars also consist of ordinary matter and quantum fluctuations. But when these ideas were first conceived, equations incorporating quantum flluctuations were not yet known, so theorists Carballo-Rubio’s stars, on the other hand, emerge naturally from a consistent set of equations based on known physics.

    Gravastars and black stars are structured differently: In gravastar cores, large quantum fluctuations push ordinary matter outward to form an ultra-thin shell at the surface. Black stars, on the other hand, balance matter and the quantum fluctuations throughout their structure.

    Carballo-Rubio’s stars are like a hybrid of the two previous ideas. “On the one hand, both matter and the quantum [fluctuations] are present throughout the structure, as in the black star model,” he says. “On the other, the star displays two distinct elements, namely a core and an ultra-thin shell, as in the gravastar model.”

    2
    Artist’s drawing of a neutron star. Casey Reed / Penn State University.

    The Question of Stability

    Whether these hybrid stars exist in the real world is a matter of debate. Carballo-Rubio’s solutions do not incorporate time, so it isn’t clear if a such a star would remain stable or rapidly morph into something else . . . like a black hole.

    “Equilibrium solutions can be found for a pen standing on its tip,” remarks relativistic astrophysicist Luciano Rezzolla (Institute of Theoretical Physics, Germany). “Such a solution is obviously unstable to small perturbations.”

    However, if Carballo-Rubio can show that his semiclassical relativistic stars are indeed dynamically stable — which he will start work on next — the next generation of gravitational wave observatories should offer the level of precision necessary in the coming decades to distinguish unconventional compact bodies from black holes, potentially providing evidence to support the existence of this new type of star.

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 2:15 pm on March 12, 2018 Permalink | Reply
    Tags: A possible experiment to prove that gravity and quantum mechanics can be reconciled, , , , , , Quantum Mechanics   

    From phys.org: “A possible experiment to prove that gravity and quantum mechanics can be reconciled” 

    physdotorg
    phys.org

    March 12, 2018
    Bob Yirka

    1
    Credit: G. W. Morley/University of Warwick and APS/Alan Stonebraker

    Two teams of researchers working independently of one another have come up with an experiment designed to prove that gravity and quantum mechanics can be reconciled. The first team is a pairing of Chiara Marletto of the University of Oxford and Vlatko Vedral of National University of Singapore. The second is an international collaboration. In the papers, both published in Physical Review Letters, the teams describe their experiment and how it might be carried out Spin Entanglement Witness for Quantum Gravity and Gravitationally Induced Entanglement between Two Massive Particles is Sufficient Evidence of Quantum Effects in Gravity.

    Gravity is a tough nut to crack, there is just no doubt about it. In comparison, the strong, weak and electromagnetic forces are a walk in the park. Scientists still can’t explain the nature of gravity, though how it works is rather well understood. The current best theory regarding gravity goes all the way back to Einstein’s general theory of relativity, but there has been no way to reconcile it with quantum mechanics. Some physicists suggest it could be a particle called the graviton. But proving that such a particle exists has been frustrating, because it would be so weak that it would be very nearly impossible to measure its force. In this new effort, neither team is suggesting that their experiment could reconcile gravity and quantum mechanics. Instead, they are claiming that if such an experiment is successful, it would very nearly prove that it should be possible to do it.

    The experiment essentially involves attempting to entangle two particles using their gravitational attraction as a means of confirming quantum gravity. In practice, it would consist of levitating two tiny diamonds a small distance from one another and putting each of them into a superposition of two spin directions. After that, a magnetic field would be applied to separate the spin components. At this point, a test would be made to see if each of the components is gravitationally attracted. If they are, the researchers contend, that will prove that gravity is quantum; if they are not, then it will not. The experiment would have to run many times to get an accurate assessment. And while a first look might suggest such an experiment could be conducted very soon, the opposite is actually true. The researchers suggest it will likely be a decade before such an experiment could be carried out due to the necessity of improving scale and the sensitivity involved in such an experiment.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) 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, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 1:18 pm on March 5, 2018 Permalink | Reply
    Tags: , , , , , Quantum Mechanics, Schrödinger Equation   

    From Caltech: “Massive Astrophysical Objects Governed by Subatomic Equation” 

    Caltech Logo

    Caltech

    03/05/2018
    Lori Dajose

    1
    Schrödinger in Space: An artist’s impression of research presented in Batygin (2018), MNRAS 475, 4. Propagation of waves through an astrophysical disk can be understood using Schrödinger’s equation – a cornerstone of quantum mechanics.
    Credit: James Tuttle Keane, California Institute of Technology

    The Schrödinger Equation makes an unlikely appearance at the astronomical scale.

    Quantum mechanics is the branch of physics governing the sometimes-strange behavior of the tiny particles that make up our universe. Equations describing the quantum world are generally confined to the subatomic realm—the mathematics relevant at very small scales is not relevant at larger scales, and vice versa. However, a surprising new discovery from a Caltech researcher suggests that the Schrödinger Equation—the fundamental equation of quantum mechanics—is remarkably useful in describing the long-term evolution of certain astronomical structures.

    The work, done by Konstantin Batygin (MS ’10, PhD ’12), a Caltech assistant professor of planetary science and Van Nuys Page Scholar, is described in a paper appearing in the March 5 issue of Monthly Notices of the Royal Astronomical Society.

    Massive astronomical objects are frequently encircled by groups of smaller objects that revolve around them, like the planets around the sun. For example, supermassive black holes are orbited by swarms of stars, which are themselves orbited by enormous amounts of rock, ice, and other space debris. Due to gravitational forces, these huge volumes of material form into flat, round disks. These disks, made up of countless individual particles orbiting en masse, can range from the size of the solar system to many light-years across.

    Astrophysical disks of material generally do not retain simple circular shapes throughout their lifetimes. Instead, over millions of years, these disks slowly evolve to exhibit large-scale distortions, bending and warping like ripples on a pond. Exactly how these warps emerge and propagate has long puzzled astronomers, and even computer simulations have not offered a definitive answer, as the process is both complex and prohibitively expensive to model directly.

    While teaching a Caltech course on planetary physics, Batygin (the theorist behind the proposed existence of Planet Nine) turned to an approximation scheme called perturbation theory to formulate a simple mathematical representation of disk evolution. This approximation, often used by astronomers, is based upon equations developed by the 18th-century mathematicians Joseph-Louis Lagrange and Pierre-Simon Laplace. Within the framework of these equations, the individual particles and pebbles on each particular orbital trajectory are mathematically smeared together. In this way, a disk can be modeled as a series of concentric wires that slowly exchange orbital angular momentum among one another.

    As an analogy, in our own solar system one can imagine breaking each planet into pieces and spreading those pieces around the orbit the planet takes around the sun, such that the sun is encircled by a collection of massive rings that interact gravitationally. The vibrations of these rings mirror the actual planetary orbital evolution that unfolds over millions of years, making the approximation quite accurate.

    Using this approximation to model disk evolution, however, had unexpected results.

    “When we do this with all the material in a disk, we can get more and more meticulous, representing the disk as an ever-larger number of ever-thinner wires,” Batygin says. “Eventually, you can approximate the number of wires in the disk to be infinite, which allows you to mathematically blur them together into a continuum. When I did this, astonishingly, the Schrödinger Equation emerged in my calculations.”

    The Schrödinger Equation is the foundation of quantum mechanics: It describes the non-intuitive behavior of systems at atomic and subatomic scales. One of these non-intuitive behaviors is that subatomic particles actually behave more like waves than like discrete particles—a phenomenon called wave-particle duality. Batygin’s work suggests that large-scale warps in astrophysical disks behave similarly to particles, and the propagation of warps within the disk material can be described by the same mathematics used to describe the behavior of a single quantum particle if it were bouncing back and forth between the inner and outer edges of the disk.

    The Schrödinger Equation is well studied, and finding that such a quintessential equation is able to describe the long-term evolution of astrophysical disks should be useful for scientists who model such large-scale phenomena. Additionally, adds Batygin, it is intriguing that two seemingly unrelated branches of physics—those that represent the largest and the smallest of scales in nature—can be governed by similar mathematics.

    “This discovery is surprising because the Schrödinger Equation is an unlikely formula to arise when looking at distances on the order of light-years,” says Batygin. “The equations that are relevant to subatomic physics are generally not relevant to massive, astronomical phenomena. Thus, I was fascinated to find a situation in which an equation that is typically used only for very small systems also works in describing very large systems.”

    “Fundamentally, the Schrödinger Equation governs the evolution of wave-like disturbances.” says Batygin. “In a sense, the waves that represent the warps and lopsidedness of astrophysical disks are not too different from the waves on a vibrating string, which are themselves not too different from the motion of a quantum particle in a box. In retrospect, it seems like an obvious connection, but it’s exciting to begin to uncover the mathematical backbone behind this reciprocity.”

    The paper is titled “Schrödinger Evolution of Self-Gravitating Disks.” Funding was provided by the David and Lucile Packard Foundation.

    See the full article here .

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

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  • richardmitnick 11:44 am on February 25, 2018 Permalink | Reply
    Tags: , Quantum Mechanics,   

    From ScienceNews: “Two-way communication is possible with a single quantum particle” 


    ScienceNews

    February 23, 2018
    Emily Conover

    Studies show two people can simultaneously swap information using only one photon

    1
    DOUBLE DUTY Thanks to the phenomenon of quantum superposition, a single particle of light can send information in two directions at once, scientists report.

    Communication is a two-way street. Thanks to quantum mechanics, that adage applies even if you’ve got only one particle to transmit messages with.

    Using a single photon, or particle of light, two people can simultaneously send information to one another, scientists report in a new pair of papers. The feat relies on a quirk of quantum mechanics — superposition, the phenomenon through which particles can effectively occupy two places at once.

    Sending information via quantum particles is a popular research subject, thanks to the promise of unhackable quantum communication (SN: 12/23/17, p. 27). The new studies specify a previously unidentified twist on that type of technique. “Sometimes you overlook a cool idea, and then it’s just literally right in front of your nose,” says University of Vienna experimental physicist Philip Walther.

    Theoretical physicists Flavio Del Santo of the University of Vienna and Borivoje Dakić from the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences describe the theory behind the procedure in the Feb. 9 Physical Review Letters. Walther, Del Santo, Dakić and colleagues follow up with a demonstration of the technique in a paper posted at arXiv.org on February 14.

    Imagine that two people, Alice and Bob, are stationed some distance apart. In standard classical physics, Alice and Bob would each require their own photon to send each other messages simultaneously, with each light particle transmitting a single bit, 0 or 1.

    But if Alice and Bob possess a photon that is in a superposition — simultaneously located near Alice and near Bob — both of them can manipulate that photon to encode a 0 or 1, and then send it back to the other. How each manipulates the photon determines which of the two receives the photon in the end. If Alice and Bob put in the same bit — both 0s or both 1s — Alice receives the photon. If their bits don’t match, Bob gets it. Since Alice knows whether she sent a 0 or a 1, she immediately knows whether Bob encoded a 0 or 1, and vice versa.

    To show that such communication is possible, Walther and colleagues sent single photons through an arrangement of mirrors and other optical devices. The setup put the photon in a superposition, sending it simultaneously to two stations that represented Alice and Bob.

    By changing the phase of the light’s electromagnetic wave — shifting where the troughs and peaks of the wave fell — the researchers encoded the photon with a 0 or 1 at each station. Then, at each station, the photon — still in limbo between Alice and Bob — was sent to the opposite station. Along the way, the photon interacted with itself, interfering like water ripples combining to amplify their strength or cancel out. That interference determined whether the final photon was detected at Alice’s station or Bob’s.

    “It’s a very nice idea,” says physicist Giulio Chiribella of the University of Oxford, who was not involved with the research. “This is another way in which quantum mechanics catches us off guard.”

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

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