Abstract
Quantum behavior of superconducting nanowires may essentially depend on the employed experimental setup. Here we investigate a setup that enables passing equilibrium supercurrent across an arbitrary segment of the wire without restricting fluctuations of its superconducting phase. The low temperature physics of the system is determined by a combined effect of collective sound-like plasma excitations and quantum phase slips. At T=0 the wire exhibits two quantum phase transitions, both being controlled by the dimensionless wire impedance g. While thicker wires with g>16 stay superconducting, in thinnest wires with g<2 the supercurrent is totally destroyed by quantum fluctuations. The intermediate phase with 2<g<16 is characterized by two different correlation lengths demonstrating superconducting-like behavior at shorter scales combined with vanishing superconducting response in the long scale limit.