Read more at: http://phys.org/news/2014-06-einstein-quantum-mechanics-hed-today.html#jCp
Albert Einstein may be most famous for his mass-energy equivalence formula E = mc2, but his work also laid down the foundation for modern quantum mechanics.
His analysis of the "spookiness" of quantum mechanics opened up a whole range of applications including quantum teleportation and quantum cryptography, but he wasn't completely convinced by the theory of quantum mechanics – and that story is as fascinating as the theory he attempted to nail down.
Quantum mechanics is downright bizarre. It implies that a particle, such as an electron, can pass through two holes at the same time.
More famously, German physicist Erwin Schrödinger's equations proved that a cat could end up in a peculiar sort of quantum state, being neither dead nor alive.
None of this impressed Einstein. He believed quantum mechanics was correct, but desperately wanted to find a way to "complete" quantum mechanics so it made sense.