The mirror inverts the break
The mirror inverts the break
In a Josephson junction, a physical barrier is introduced. A superconducting wire is deliberately broken, severed by a nanometer-thin wall of insulating oxide. The metal stops, but the current does not. Through the strange grace of quantum mechanics, the electrical charge simply tunnels across the void, passing through the solid insulator as if it were not there.
The Quantum Phase Slip is the exact electrodynamic mirror of this phenomenon.
In a QPS nanowire, there is no physical break. The superconducting wire is continuous, unbroken, and perfectly solid. But because the wire is unimaginably thin—narrower than the coherence length of the Cooper pairs themselves—the quantum state of the metal becomes fragile.
Under the strain of a bias current, the superconducting order parameter can violently fluctuate. For a fraction of a picosecond, the superconductivity at a single microscopic point simply vanishes. The metal is still there, but its quantum state is broken.
In that fleeting moment of vulnerability, the universe balances the dual equations of electromagnetism. Just as a physical break allows charge to tunnel across an insulator, a quantum break allows a magnetic flux quantum to tunnel through the solid wire. The barrier is not a physical wall, but a collapse of the state itself; the ghost does not leap the gap, the gap leaps the ghost.