The universe really is weird, which is bad news for Albert Einstein and would-be hackers hoping to break into quantum encryption systems.

Eighty years after Einstein dismissed the idea of quantum entanglement as "spooky", Dutch scientists say they have proved the effect is real, and that simply observing one particle can instantly change another far-away object.



Researchers detailed an experiment in the journal Nature this week that showed how two electrons at separate locations 1.3 km apart on the Delft University of Technology campus demonstrated a clear, invisible and instantaneous connection.



Importantly, the new study closed loopholes in earlier tests that had left some doubt as to whether the eerie connection predicted by quantum theory was real or not.

Einstein famously insisted, in a 1935 scientific paper, that what he called "spooky action at a distance" had to be wrong, and that there must be undiscovered properties of particles to explain such counter-intuitive behaviour.

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The idea certainly confounds our day-to-day experience of the world, where change only appears to occur through local interactions. But in recent decades, scientific evidence has been building that particles can indeed become "entangled" so that no matter how far apart they are, they will always be connected.



The Delft experiment is conclusive because, for the first time, scientists have closed two potential loopholes at once.



The first suggested that particles could somehow synchronise behaviour ahead of time, while the second implied that testing might detect only a subset of prepared entangled pairs.



To prove their case, the team led by Delft professor Dr Ronald Hanson used two diamonds containing tiny traps for electrons with a magnetic property called 'spin' and measured all entangled pairs across the 1.3 km separating two laboratories.



The experiment effectively closes a chapter in an 80-year scientific debate, but Dr Hanson said it also had important implications for the future, since sophisticated cryptography is already using quantum properties to guarantee data security.



Such quantum encryption systems will only be 100 per cent secure, however, if all loopholes are closed, as in the Delft system.



"Loopholes can be backdoors into systems," Dr Hanson said.

"When you go loophole-free then you add an extra layer of security and you can be absolutely certain there is no way for hackers to get in."

Reuters