'Ingenious' Experiment Closes Loopholes In Quantum Theory

Annanag writes: A Bell experiment in the Netherlands has plugged loopholes in the theory of quantum mechanics using a technique called entanglement swapping to combine the benefits of using both light and matter. It's Nobel-Prize winning stuff. Quoting: "Experiments that use entangled photons are prone to the ‘detection loophole’: not all photons produced in the experiment are detected, and sometimes as many as 80% are lost. Experimenters therefore have to assume that the properties of the photons they capture are representative of the entire set. ...

[In the new work], researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometers apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location. There, the two photons were entangled with each other — and this caused both their partner electrons to become entangled, too.

This did not work every time. In total, the team managed to generate 245 entangled pairs of electrons over the course of nine days. The team's measurements exceeded Bell’s bound, once again supporting the standard quantum view. Moreover, the experiment closed both loopholes at once: because the electrons were easy to monitor, the detection loophole was not an issue, and they were separated far enough apart to close the communication loophole, too."

Comments

Loopholes in the experiments not the theory

[Barbecue911]

I'm not an quantum physicist, but the loopholes appear to be in the experiments intended to demonstrate the "spookiness" of quantum theory, not the theory itself:

The first Bell test was carried out in 1981, by Alain Aspect’s team at the Institute of Optics in Palaiseau, France. Many more have been performed since, always coming down on the side of spookiness — but each of those experiments has had loopholes that meant that physicists have never been able to fully close the door on Einstein’s view.

Re:Is quantum mechanics a theory?

[Anonymous Coward]

Gravity is just a label we put on the phenomenon that causes the cannonballs to fall. We don't know why this phenomenon emerges, thus we don't know why cannonballs fall.

Entanglement

[Anonymous Coward]

A lot of quantum confusion can be dispelled by realizing that particles don't really exist. There are a bunch of phenomenae that look like particles, but also look like wavelike perturbations of a field. Since we don't really have any good mental analogies of what's "really" happenening, we have to fall back on mathematical descriptions. So the general concept is that you can glom two waves/particles together so that you cannot describe them individually any more. From my limited understanding, I don't think there's a mechamism so much as it's inherent to quantum mechanics to be able to construct systems like this.

This is huge

[iris-n]

Guys, this is huge. People have been doing versions of this experiment for decades, every time making it more refined, in order to be able to reach the striking conclusion with the fewest possible assumptions: that the world is not deterministic. The quantum randomness is not our ignorance, is a fundamental property of nature.

What they did was to violate a Bell inequality, without using the most questionable extra assumptions (called loopholes) people normally use to extract a conclusion from this experiment: that the separated laboratories are not somehow communicating to conspire to produce the desired outcome, or that the photons they detect are indeed a good representative of all the photons that were emitted in the experiment (normally people can detect only a small fraction of the photons).

I am a quantum physicist, and I know the science behind this experiment very well. If anybody wants to ask me anything, I'd be glad to oblige.