Quantum phase slip noise
Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩdecreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T→0. The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω.