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Entanglement Makes Quantum Particles Measurably Heavier, Says Quantum Theorist
KentuckyFC writes: Physicists have long hoped to unify the two great theories of the 20th century: general relativity and quantum mechanics. And yet a workable theory of quantum gravity is as far away as ever. Now one theorist has discovered that the uniquely quantum property of entanglement does indeed influence a gravitational field and this could pave the way for the first experimental observation of a quantum gravity phenomenon. The discovery is based on the long-known quantum phenomenon in which a single particle can be in two places at the same time. These locations then become entangled — in other words they share the same quantum existence. While formulating this phenomenon within the framework of general relativity, the physicist showed that if the entanglement is tuned in a precise way, it should influence the local gravitational field. In other words, the particle should seem heavier. The effect for a single electron-sized particle is tiny — about one part in 10^37. But it may be possible to magnify the effect using heavier particles, ultrarelativistic particles or even several particles that are already entangled.
FWIW, it appears from the paper that this extra "mass" is an artifact of analyzing entangled particles in a linearized gravity framework and observing a stress-energy tensor term that seems to appear higher for entangled particles and radiated away as particles move to decoherence. This perhaps might be considered the mass of the entanglement.
On the other hand, wouldn't it be cool if the reason for the observed equivalency of gravitational mass and inertial mass was somehow related to quantum entanglement? (yes I know this is unrelated to this phenomena, but still)...
The photon has zero rest mass, yes.
E = mc**2 is a nice popularization; it's also wrong. It's actually E**2=(mc**2)**2 + (pc)**2, where p is the momentum. When momentum is zero, you can usually simplify this to E=mc**2, but a photon's existence is defined mostly by its momentum. Since m is zero for a photon, this means the energy of a photon is given by entirely by E=pc.
Hope this helps!