I've always assumed that "quantum locking" was a term invented by the writers of Dr Who, but this video suggests otherwise.
What is quantum locking? Is it real?
Answer
Apparently, a key detail is that the superconducting layer on the disk is very thin.
Usually superconducting levitation demonstrations use thicker layers of superconductors which completely deflect the field from magnets - so they float above the magnet but also tend to wobble around a bit.
This demo uses a very thin superconducting layer - this allows the magnetic field to penetrate the superconductor at a small number of defect sites. The small but non-zero magnetic field passing through the defect sites 'locks' the superconductor into whatever orientation is set initially - and also prevents the wobbly shaking normally seen in Meisner-effect levitation.
See: http://io9.com/5850729/quantum-locking-will-blow-your-mind--but-how-does-it-work
No 'Weeping Angels' are involved.
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