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When talking about quantum physics, people will often nonchalantly say that particles can be in two places at once. Physicist Sabine Hossenfelder explores what is actually going on.
Ten years ago this week, two international collaborations of groups of scientists, including a large contingent from Caltech, confirmed that they had found conclusive evidence for the Higgs boson, an elusive elementary particle, first predicted in a series of articles published in the mid-1960s, that is thought to endow elementary particles with mass.
Fifty years prior, as theoretical physicists endeavored to understand the so-called electroweak theory, which describes both electromagnetism and the weak nuclear force (involved in radioactive decay), it became apparent to Peter Higgs, working in the UK, and independently to François Englert and Robert Brout, in Belgium, as well as U.S. physicist Gerald Guralnik and others, that a previously unidentified field that filled the universe was required to explain the behavior of the elementary particles that compose matter. This field, the Higgs field, would lead to a particle with zero spin, significant mass, and have the ability to spontaneously break the symmetry of the earliest universe, allowing the universe to materialize. That particle became known as the Higgs boson.
Scientists at Tokyo Institute of Technology designed a new type of molecular wire doped with organometallic ruthenium to achieve unprecedentedly higher conductance than earlier molecular wires. The origin of high conductance in these wires is fundamentally different from similar molecular devices and suggests a potential strategy for developing highly conducting “doped” molecular wires.
Since their conception, researchers have tried to shrink electronic devices to unprecedented sizes, even to the point of fabricating them from a few molecules. Molecular wires are among the building blocks of such minuscule contraptions, and many researchers have been developing strategies to synthesize highly conductive, stable wires from carefully designed molecules.
A team of researchers from Tokyo Institute of Technology, including Yuya Tanaka, designed a novel molecular wire in the form of a metal electrode-molecule-metal electrode (MMM) junction including a polyyne, an organic chain-like molecule, “doped” with a ruthenium-based unit Ru(dppe)2. The proposed design, featured in the cover of the Journal of the American Chemical Society, is based on engineering the energy levels of the conducting orbitals of the atoms of the wire, considering the characteristics of gold electrodes.
A major goal in the field of molecular electronics, which aims to use single molecules as electronic components, is to make a device where a quantized, controllable flow of charge can be achieved at room temperature. A first step in this field is for researchers to demonstrate that single molecules can function as reproducible circuit elements such as transistors or diodes that can easily operate at room temperature.
A team led by Latha Venkataraman, professor of applied physics and chemistry at Columbia Engineering and Xavier Roy, assistant professor of chemistry (Arts & Sciences), published a study in Nature Nanotechnology that is the first to reproducibly demonstrate current blockade—the ability to switch a device from the insulating to the conducting state where charge is added and removed one electron at a time—using atomically precise molecular clusters at room temperature.
Bonnie Choi, a graduate student in the Roy group and co-lead author of the work, created a single cluster of geometrically ordered atoms with an inorganic core made of just 14 atoms—resulting in a diameter of about 0.5 nanometers—and positioned linkers that wired the core to two gold electrodes, much as a resistor is soldered to two metal electrodes to form a macroscopic electrical circuit (e.g. the filament in a light bulb).
The ability to turn superconductivity off and on with a literal flip of a switch in so-called “magic-angle twisted graphene” has allowed engineers at Caltech to observe an unusual phenomenon that may shed new light on superconductivity in general.
The research, led by Stevan Nadj-Perge, assistant professor of applied physics and materials science, was published in the journal Nature on June 15.
Magic-angle twisted graphene, first discovered in 2018, is made from two or three sheets of graphene (a form of carbon consisting of a single layer of atoms in a honeycomb-like lattice pattern) layered atop one another, with each sheet twisted at precisely 1.05 degrees in relation to the one below it. The resulting bilayer or trilayer has unusual electronic properties: for example, it can be made into an insulator or a superconductor depending on how many electrons are added.
Martin ChartrandListen to the sound, more like a musket than a 3D printed plastic gun.
Second video shows the attempted assassination of former Japanese Prime Minister Shinzo Abe
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Continue reading “Physicists discover a ‘family’ of robust, superconducting graphene structures” »
The LUX-ZEPLIN detector searched for elusive WIMP particles for 60 days on its first scientific run. Did it detect dark matter?
Researchers in Germany have demonstrated quantum entanglement of two atoms separated by 33 km (20.5 miles) of fiber optics. This is a record distance for this kind of communication and marks a breakthrough towards a fast and secure quantum internet.
Quantum entanglement is the uncanny phenomenon where two particles can become so inextricably linked that examining one can tell you about the state of the other. Stranger still, changing something about one particle will instantly alter its partner, no matter how far apart they are. That leads to the unsettling implication that information is being “teleported” faster than the speed of light, an idea that was too much for even Einstein, who famously described it as “spooky action at a distance.”
Despite its apparent impossibility, quantum entanglement has been consistently demonstrated in experiments for decades, with scientists taking advantage of its bizarre nature to quickly transmit data over long distances. And in the new study, researchers from Ludwig-Maximilians-University Munich (LMU) and Saarland University have now broken a distance record for quantum entanglement between two atoms over fiber optics.
‘The more analyses we perform, the more kinds of exotic hadrons we find’
In the last two years, researchers have discovered a tetraquark made up of two charm quarks and two charm antiquarks, and two “open-charm” tetraquarks consisting of a charm antiquark, an up quark, a down quark and a strange antiquark.
“The more analyses we perform, the more kinds of exotic hadrons we find. We’re witnessing a period of discovery similar to the 1950s, when a ‘particle zoo’ of hadrons started being discovered and ultimately led to the quark model of conventional hadrons in the 1960s. We’re creating ‘particle zoo 2.0,” LHCb physics coordinator Niels Tuning said in a statement.
Continue reading “Cern physicists find evidence of three new ‘exotic’ particles” »
A network in which data transmission is perfectly secure against hacking? If physicists have their way, this will become reality one day with the help of the quantum mechanical phenomenon known as entanglement. For entangled particles, the rule is: If you measure the state of one of the particles, then you automatically know the state of the other. It makes no difference how far away the entangled particles are from each other. This is an ideal state of affairs for transmitting information over long distances in a way that renders eavesdropping impossible.
A team led by physicists Prof. Harald Weinfurter from LMU and Prof. Christoph Becher from Saarland University have now coupled two atomic quantum memories over a 33-kilometer-long fiber optic connection. This is the longest distance so far that anyone has ever managed entanglement via a telecom fiber.
The quantum mechanical entanglement is mediated via photons emitted by the two quantum memories. A decisive step was the researchers’ shifting of the wavelength of the emitted light particles to a value that is used for conventional telecommunications. “By doing this, we were able to significantly reduce the loss of photons and create entangled quantum memories even over long distances of fiber optic cable,” says Weinfurter.
