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To save time and dredging through pop-sci journalism for those who have some background knowledge already: https://journals.aps.org/prl/abstract/10.1103/PhysRe

• ianai 9y ago
  And to rip off the abstract “We show that despite the weakness of gravity, the phase evolution induced by the gravitational interaction of two micron size test masses in adjacent matter-wave interferometers can detectably entangle them even when they are placed far apart enough to keep Casimir-Polder forces at bay. We provide a prescription for witnessing this entanglement, which certifies gravity as a quantum coherent mediator, through simple spin correlation measurements.”
  • kurthr 9y ago
    A key point is that they have not measured the effect yet so it's not known whether the entanglement will be measured. Both papers describe a gravitational entanglement detection through measurement of evolution of a separate quantum phenomenon (e.g. nitrogen spin in a diamond lattice). One challenge, which is commonly a problem for laboratory gravitational experiments, is that many other force interactions dominate over short distance scales (electric, magnetic, or even vibrational phonons) so excluding those is critical to showing the entanglement is gravitational. This means near perfect electrical, magnetic, and vibrational isolation... and probably measuring their coupling amplitude them to show that it is perfect. As usual in experimental physics, the problem is not in detecting the effect, but in not detecting all the other interfering effects. It borders on proving a negative.
    • ianai 9y ago
      Having not seen this sort of theory before, it felt as though the sort of thing that may be a widespread hypothesis but the data are prohibitive to collect.
      • kurthr 9y ago
        They have teams working on it now, but experiment is notoriously more expensive than theory.