Category Archives: Atomic physics

IceCube collaboration confirms first sighting of neutrinos from space

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New Scientist: Scientists have determined that two high-energy neutrinos detected by the South Pole IceCube Neutrino Observatory originated in outer space. Since the discovery of “Bert and Ernie” last year, the IceCube collaboration has been reexamining the data gathered from May 2010 to May 2012. So far they have found 26 more neutrinos of about 50 TeV each. Because that’s twice the expected number of atmospheric neutrinos, which are produced by cosmic rays hitting Earth’s atmosphere, about half must be coming from outside the solar system, according to IceCube team member Thomas Gaisser of the University of Delaware in Newark. Another indication that the neutrinos traveled a great distance is their distribution: Neutrinos are created with a well-defined flavor—either electron, muon, or tau—but can oscillate among the three flavors as they travel through space. The fact that the three types were equally represented indicates that they came a long way. As neutrinos only weakly interact with other matter, they may be able to be used to observe phenomena that optical telescopes cannot, such as the sources of cosmic rays, dark matter and dark holes, and stellar explosions.

Photon cloning may compromise quantum cryptography

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New Scientist: Although quantum cryptography has been touted as a method of secure communication, it may be susceptible to eavesdropping, according to a paper published in Physical Review Letters. Quantum cryptographic techniques rely on a fundamental principle of quantum mechanics—namely, that the act of measuring quantum data disturbs the data. Therefore, any attempt by a hacker to intercept a message compromises the transmittal. However, even the best systems will always have some margin of error. Now a quantum cloner has been developed that can create copies of a quantum-encrypted message’s photons that, although not perfect, are good enough to keep the transmission error rate relatively low. Only by closely monitoring the rate of error can the counterfeits be detected.

IBM uses carbon atoms to create world’s smallest movie

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BBC: Researchers at IBM invented the scanning tunneling microscope (STM), for which they won the Nobel Prize in Physics in 1986. Advances in the technology, which allows for the imaging and manipulation of individual atoms, are being applied to data storage. The microscope moves an electrically charged, very small-tipped needle over a surface and maps the location of atoms when the tip is close enough that the charge tunnels to the atom. By moving the tip even closer to the atom, the microscope can be used to push the atom to a new location. To demonstrate the capabilities that the technology has achieved, a team led by Andreas Heinrich of IBM Research in Almaden, California, worked 18-hour days for two weeks to create a short, stop-motion movie. Called A Boy and His Atom, the 242-frame, 90-second-long video shows a stick figure playing with a ball. The series of still images is created from dozens of carbon atoms arranged on a sheet of copper, to which the carbon atoms bond. Between frames, the researchers use an STM to carefully move the atoms around, which then rebond to the copper sheet and are imaged in their new positions. Heinrich admits that the movie isn’t about any particular breakthrough, but is more about getting people interested and excited about technology.

IceCube detector spots highest-energy neutrinos ever

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Ars Technica: Two neutrino-induced events with energy greater than 1 PeV have been reported by researchers at the IceCube Neutrino Observatory located at the South Pole. The observation is significant because it is likely the neutrinos originated in some high-energy event distant from Earth. Trillions of neutrinos, which emanate from a number of sources such as nuclear reactions in the Sun, pass through Earth every second. But they are extremely difficult to detect because they almost never interact with normal matter. Embedded in Antarctic ice, IceCube’s strings of photodetectors watch for the telltale emission of Cherenkov radiation when a neutrino passing through happens to collide with an atom in the ice. Most of the high-energy neutrinos detected by IceCube have come from cosmic rays colliding with atoms in Earth’s atmosphere. Because of the extremely high energy of the newly detected neutrinos, however, researchers believe they may be the first indication of an astrophysical high-energy neutrino flux—an extremely energetic event that occurs far out in the universe. Longer sampling times and more data will be required to verify that finding.

Diamonds used for qubit entanglement over distance

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Nature: Entangling quantum bits (qubits) at a distance has been done before, but most such demonstrations have used materials or systems that are not easily scalable. Ronald Hanson of Delft University of Technology in the Netherlands and his colleagues have now demonstrated the ability to entangle qubits in diamond crystals 3 m apart. Qubits, which are the basis for quantum computing, allow more than just a single bit of data to be encoded at one time. Entangling qubits over a distance may allow for the development of quantum communication systems with extreme levels of encryption and significantly faster transmission of information. The system demonstrated by Hanson and his colleagues is not very efficient, achieving entanglement only one time in every 10 million attempts (or about once every 10 minutes), and requires extremely low temperatures. However, once entangled, the qubits can be stored in the diamonds at room temperatures.

Should the Higgs boson be renamed?

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BBC: Speculation surrounding this year’s Nobel Prize in Physics has rekindled the debate concerning the naming of the Higgs boson. Because key contributions were made by at least six people—Robert Brout (who died in 2011), François Englert, Gerald Guralnik, Carl Hagen, Peter Higgs, and Tom Kibble—many in the community object to the particle’s being named for just one of them. Yet naming it after all six would be unwieldy. Because the Higgs theory may be the focus of this year’s Nobel, and a maximum of three individuals can share the prize, the controversy over what to call the new particle is heating up.

Light trapped in metamaterial for first time

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MIT Technology Review: Electromagnetic waves were first trapped in the 1990s. The complex setups for doing so involve ultracold atomic gases, such as cesium and rubidium, and systems of lasers that take advantage of electromagnetically induced transparency. Now Toshihiro Nakanishi of Kyoto University in Japan and his colleagues have demonstrated a similar effect in a metamaterial made of repeating units of two variable capacitors. When both capacitors are set to the same frequency, incoming electromagnetic waves of that frequency are absorbed and trapped. Detuning the capacitors releases the waves and maintains the phase distribution of the absorbed waves. The team’s metamaterial is a three-layer deep proof-of-concept device that they successfully tested with microwaves. They believe that further work could produce a material that could trap optical frequencies or that could release waves of arbitrary shape and polarization. Those capabilities could be useful in information storage and quantum optics.

Synchrotron used to help construct synthetic vaccine

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BBC: A collaboration of researchers in the UK has been able to create a fully synthetic vaccine for foot-and-mouth disease, a serious and contagious condition that afflicts cloven-hoofed animals. The researchers used x rays generated by the Diamond Light Source synchrotron to obtain a highly detailed, atomic-level understanding of the protein shell of the foot-and-mouth virus, a member of the picornavirus family. With that knowledge, they were able to construct a synthetic version of the virus consisting of an empty shell and lacking any of the internal RNA that makes viruses dangerous. Because the resulting vaccine has no live virus, there is no risk of infection, and animals given the vaccine can be easily distinguished from those that are infected. The researchers also reinforced the synthetic virus’s shell, which makes the vaccine stable for several hours, even at high temperatures. The vaccine is therefore very useful in places like southeast Asia, where foot-and-mouth disease is endemic. Also in the picornavirus family is polio, which has not yet been completely eradicated. The current polio vaccine uses a live virus and so carries the risk of potentially reestablishing itself. If the technique used to create the foot-and-mouth vaccine can also be used for polio and other similar viruses, such risks can be mitigated.

US produces first non-weapons-grade plutonium in 25 years

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Discovery News: It has been 25 years since the Department of Energy closed the Savannah River Site, the last source of non-weapons-grade plutonium-238 in the US. Since then, the US has been using up its stockpiles and obtaining plutonium through trade with Russia. The deal with Russia ended in 2010, however. Beginning in the 1970s, NASA used plutonium-238 to supplement solar panels as a power source in spacecraft, including probes such as Voyager 1 and 2, Galileo, and Cassini, and the Martian landers Viking and Curiosity. After the end of the trade deal with Russia, DOE and NASA began working to redevelop a plutonium production system at Oak Ridge National Laboratory. The agencies believe that the process of irradiating neptunium in the reactors at the laboratory will produce roughly 1.5 kg of plutonium-238 every year. The newly produced plutonium will then be mixed with the remaining stockpile, which will restore the older plutonium to a usable property density. So for every 1 kg of new production, 2 kg of the stockpile will be revived. NASA already intends to use plutonium in its next Martian rover, planned for launch in 2020.

Studying exotic zinc atoms to elucidate neutron stars

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Science News: The origin of neutron-rich heavy elements in the universe remains a mystery. One possible source could be neutron stars, whose high-pressure, high-gravity interiors could stabilize atoms that could not form otherwise. Collisions between neutron stars would then disperse the atoms into space. Because neutron stars are too far away to study, scientists are trying to determine their composition via computer simulations using the properties of exotic isotopes created in particle accelerators. One such isotope, thought to exist in the crust of neutron stars, is zinc-82. Using a facility at CERN, Robert Wolf of the University of Greifswald in Germany and colleagues were able to isolate a pure sample of zinc-82 and determine its mass. By comparing the mass with predictions from computer modeling, the researchers were able to rule out zinc-82 as a constituent of neutron stars. Despite the negative result, the technique shows potential for “pin[ning] down the characteristics of other exotic nuclei that may exist in neutron stars,” writes Andrew Grant for Science News.