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Quantum entanglement effects observed over 100s of miles

posted by Jason Kottke   Jun 19, 2017

A group of Chinese scientists say they have demonstrated the effects of quantum entanglement over a distance of 1200 km (745 miles).

Entanglement involves putting objects in the peculiar limbo of quantum superposition, in which an object’s quantum properties occupy multiple states at once: like Schrodinger’s cat, dead and alive at the same time. Then those quantum states are shared among multiple objects. Physicists have entangled particles such as electrons and photons, as well as larger objects such as superconducting electric circuits.

Theoretically, even if entangled objects are separated, their precarious quantum states should remain linked until one of them is measured or disturbed. That measurement instantly determines the state of the other object, no matter how far away. The idea is so counterintuitive that Albert Einstein mocked it as “spooky action at a distance.”

What’s weird to me is that all the articles I read about this touted that this happened in space, that an ultra-secure communications network was possible, or that we could build a quantum computer in space. Instantaneous communication over a distance of hundreds of miles is barely mentioned. Right now, it takes about 42 minutes for a round-trip communication between the Earth and Mars (and ~84 minutes for Jupiter). What if, when humans decide to settle on Mars, we could send a trillion trillion quantum entangled particles along with the homesteaders that could then be used to communicate in real time with people on Earth? I mean, how amazing would that be?

Update: Well, the simple reason why these articles don’t mention instantaneous communication at distance is that you can’t do it, even with quantum entanglement.

This is one of the most confusing things about quantum physics: entanglement can be used to gain information about a component of a system when you know the full state and make a measurement of the other component(s), but not to create-and-send information from one part of an entangled system to the other. As clever of an idea as this is, Olivier, there’s still no faster-than-light communication.

(thx, everyone)