In this issue: New Light on Spacetime Wormholes, Modeling How Cells Grow Old, Catching Dark Matter with an Electrical Circuit, Picking the Brain, How Long Does a Neutron Live, What Accelerates Electrons in the Earth’s Radiation Belt, Computing with Entangled Ions
* Please note that there will be no tip sheet next week (Nov 26th). The tip sheet will be back on Dec. 3rd.
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New Light on Space-time Wormholes
(Image credit: APS/Alan Stonebraker)
New theoretical results suggest a connection between quantum mechanical entanglement and the space-time wormholes predicted by general relativity.
The concept of entanglement – a perplexing consequence of quantum mechanics – has been used to explain a number of experimental observations with photons, electrons and molecules and the basis of all quantum communication and computing schemes. Now, two independent studies, by researchers in the US and Canada, explain how entanglement may be tied to another paradoxical idea: the existence of “wormholes”, hypothetical shortcuts through space-time connecting black holes, a prediction of general relativity. The result supports the idea that entanglement is related to the very fabric of space-time, which in turn may provide clues on possible links between quantum mechanics and general relativity.
* Kristan Jensen (contact author), Andreas Karch, “The holographic dual of an EPR pair has a wormhole”, Physical Review Letters (expected publication date: Nov 20)
** Julian Sonner (contact author), “Holographic Schwinger effect and the geometry of entanglement”, Physical Review Letters (expected publication date: Nov 20)
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Modeling How Cells Grow Old
Researchers have developed a statistical model that describes how parts of the chromosomes called telomeres shorten with time - a process that may play a key role in senescence.
Telomeres are DNA sequences that protect the ends of chromosomes from deterioration or unwanted fusion with other chromosomes. They are thought to play a role in the aging of cells (senescence): since telomeres shorten at each cell division, a cell can only replicate a finite number of times. A research team in Paris has developed a statistical method that describes telomere shortening during cell division. The model predicts the distribution of telomere lengths in a population of dividing cells and relates such distribution to the presence of an enzyme called telomerase. The approach may help extract from experimental observations the key biological factors that regulate telomere length and thus the onset of senescence.
* K Dao Duc, David Holcman (contact author), “Computing the length of the shortest telomere in the nucleus”, Physical Review Letters (expected publication date: Nov 25)
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Catching Dark Matter with an Electrical Circuit
Certain dark matter particles may be detected by a small superconducting circuit, according to a theoretical proposal.
Several ongoing experiments, based on massive detectors, are attempting to identify the faint fingerprints of dark matter. But one of the leading candidate particles for dark matter may be revealed by a much smaller benchtop detector, according to a proposal by a researcher at the University of Cambridge (UK). The author’s calculations show that axions – a proposed component of dark matter – could leave a detectable signal when passing through a Josephson junction, a device made of two superconductors separated by a thin insulating barrier. He also suggests such a signal may have already been observed in a 2004 experiments, which revealed a signal of unknown origin that could now be interpreted as the indication of an axion with a certain mass.
* Christian Beck (contact author), “Possible resonance effect of axionic dark matter in S/N/S Josephson junctions”, Physical Review Letters (expected publication date: Dec 2)
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Picking the Brain
A mathematical analysis explains why the brain can be modeled using only a few key active regions.
To describe the complex architecture of the brain, researchers often employ a coarse model based on a few “regions of interest” – for instance those brain areas that are most active during a specific task. But is this approach, which is based on an empirical and arbitrary choice of such regions, sound? The theoretical work of a researcher at the University of Sydney (Australia) suggests the method can be put on more solid ground. Using techniques borrowed from quantum mechanics, he shows how the complex equations describing brain dynamics can be rigorously reduced to a representation based on few dominant modes (the region of interests). The theory provides a systematic approach for selecting such regions, which may lead to better brain models.
* Peter A Robinson (contact author), “Discrete-network versus modal representations of brain activity: Why a sparse regions-of-interest approach can work for analysis of continuous dynamics”, Physical Review E (expected publication date:Nov 26)
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How Long Does a Neutron Live?
An isolated neutron lives for about 15 minutes, before decaying into an electron and a proton, but some controversy exists on the exact lifetime: values obtained by two types of experiments differ by 8 seconds. By analyzing a 2005 experiment, scientists at NIST have reduced the measurement error of one of such methods to about 2 seconds, which confirms the discrepancy with the other method. Solving such discrepancy will be crucial since the free neutron lifetime is related to fundamental questions in particle physics and astrophysics, such as the rate of nucleosynthesis during the big bang.
* Andrew T Yue (contact author) et al, “Improved Determination of the Neutron Lifetime”, Physical Review Letters (expected publication date: Nov 27)
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What Accelerates Electrons in the Earth’s Radiation Belt
The Van Allen Probes – NASA spacecraft designed to characterize the Earth’s radiation belt – have observed the formation of transient, intense bursts of so-called “double layers”, structures consisting of two parallel layers of particles with opposite charge that create a strong electric field. The observation suggests such double layers may provide one of the key steps through which electrons in the Earth’s magnetosphere are accelerated to relativistic speeds. Similar double layers may also be important in radiation belts of planets such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in other astrophysical objects.
* Forrest S Mozer (contact author) et al, “Megavolt parallel potentials arising from double layer streams in the Earth’s outer radiation belt”, Physical Review Letters (expected publication date: Dec 2)
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Computing with Entangled Ions
Measurement-based quantum computing (MBQC) – a technique that processes information via sequences of measurements on single qubits - is expected to have significant advantages over other quantum computing approaches. Experimental MBQC demonstrations have so far used entangled photons, but these are hard to prepare in the large numbers needed for computation purposes. Now, for the first time, researchers In Austria have performed MBQC with trapped ions. The team entangled several ionic qubits and demonstrated a set of basic measurements that can be combined to produce any arbitrary logic function.
* Ben P Lanyon (contact author) et al, “Measurement-based quantum computation with trapped ions”, Physical Review Letters (expected publication date: Nov 19)
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