Josephson junction

Definition

A Josephson junction is a quantum mechanical device made up of two superconducting materials separated by a thin insulating barrier. It allows the tunneling of Cooper pairs, leading to unique electrical properties such as zero-voltage current and quantized voltage steps.

5 Must Know Facts For Your Next Test

1. Josephson junctions exhibit the Josephson effect, where a supercurrent flows without any voltage applied.
2. The critical current is the maximum supercurrent that can pass through the junction before resistance appears.
3. They are used in applications like SQUIDs (Superconducting Quantum Interference Devices) for extremely sensitive magnetometers.
4. The AC Josephson effect occurs when a constant voltage is applied, resulting in an oscillating current with frequency proportional to the applied voltage.
5. Josephson junctions have applications in quantum computing as qubits due to their coherent quantum state manipulation capabilities.

Review Questions

• What physical phenomenon allows a Josephson junction to conduct a supercurrent without any applied voltage?
• How does the critical current affect the behavior of a Josephson junction?
• Name one practical application of Josephson junctions in modern technology.

Related terms

Superconductor: A material that can conduct electricity with zero resistance below a certain critical temperature.

Cooper Pair: A bound pair of electrons that enables superconductivity by moving through a lattice without scattering.

SQUID: A Superconducting Quantum Interference Device used for measuring extremely subtle magnetic fields with high precision.