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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.
Yo mama's so fat her wave function collapses into multiple eigenstates.
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The size of the visible universe is only on the order of 10^9 light years, so that won't do it. But combine it with the range of the weak force, which has been measured and our direct measurement capability spans a range of about 10^39 (weak force ~= 10^-18 meters, lightyear ~= 10^12 meters, visible universe ~= 10^9 lightyears) so we can at least comprehend this number in a concrete way. Measuring it even indirectly... not going to happen with your basic bathroom scale. But we are talking about finding a way to relate effects on the Planck scale to the cosmogical scale so big exponents should be unsurprising. Unlike the outspoken AC above I will wait for peer review before adjusting my bullshit meter. Naturally, we all want to believe there is some big breakthrough here after the endless low calorie diet of contrived mathematical attempts to unify the big theories for the last too many decades. Is this one it? Seems unlikely just based on the long run of failed attempts. But I will just sit back with popcorn and enjoy the show. At worst, a refreshing break from the usual multidimensional mathematical salad parade. I'm particularly interested in more eplanation of how two entangled particles became one, at least according to the press.
When all you have is a hammer, every problem starts to look like a thumb.
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)...
Either way, I should have it done by lunch time.
Or we could spend some time coming up with additional consequences that might allow indirect tests. For example, does this effect have any consequences for the spectrum of Hawking radiation (just to consider one area were entangled pairs and high gravitational fields are involved)?
How about the structure of the very early universe?
Or are there ridiculously subtle interferometric effects that might allow the detection of the phenomenon? Or other quantum effects?
Consider the Mossbauer Effect as an example of measuring stupidly small energy splittings so many orders of magnitude below any reasonable detector resolution that no doubt some smug bastard made fun of the people doing the hard work of calculating them "because no one will ever be able to measure that!"
Blasphemy is a human right. Blasphemophobia kills.
Your question doesn't have a simple answer, but if it did, it would involve signal-to-noise ratio within a given bandwidth. A radio receiver with a bandwidth in the audio range (~10 kHz) can amplify a signal by about ten trillion times its original power or a few million times its original voltage, before hitting the thermal noise floor of -174 dBm/Hz. These figures aren't exact (for one thing, they neglect the impedance change from a 50-ohm antenna input to an 8-ohm speaker) but the basic idea is correct: the noise floor at 25C in a 50-ohm system is -174 dBm/Hz + 10*log(bandwidth) dBm.
You can improve SNR by making your measurement near absolute zero, but you can't get rid of the noise entirely because some of it isn't strictly thermal in nature. Synchronous demodulation can let you recover information from below the noise floor, given a carrier of known phase. There are other tricks and hacks, but the bottom line is that you are still going to be at least ten or fifteen orders of magnitude away from being able to work with 37 significant figures in any real-world physical measurement. Integration times for such a measurement would have to approach heat-death-of-the-Universe durations.
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!