Muons are radioactive particles which behave like tiny magnets. They can be implanted in matter and are sensitive to local magnetic fields. In this way we can explore quantum decoherence through spin systems, since the spin-polarised muon behaves like a qubit, and its spin-relaxation allows us to deduce how quantum information spreads out in a network of spins. We are using this idea to study spin liquids, highly entangled networks of magnetic spins where geometric frustration prevents long-range order but leads to complex correlations between the spins.
