Detecting dual superconductivity in the ground state of gauge theory

We explicitly construct a monopole creation operator: its vacuum expectation value is a disorder parameter for dual superconductivity, in that it signals a spontaneous breaking of the U(1) symmetry corresponding to monopole charge conservation. This operator is tested by numerical simulations in compact U(1) gauge theory. Our construction provides a general recipe for detection of the condensation of any topological soliton. In particular our operator can be used to detect dual superconductivity of the QCD vacuum.