DC SQUID Flux Interference

Distinguish a SQUID’s phase-dependent current from its flux-dependent critical envelope. A Direct Current Superconducting QUantum Interference Device (DC SQUID) uses two Josephson junctions in a superconducting loop. The total current depends both on the common mean phase and the applied magnetic flux.

Experiment

Open the DC SQUID Flux Interference module. Test the dependence of the total current on phase and flux asymmetry.

1. Set Flux quanta to 0.5.
2. Set Junction ratio to 1 (symmetric junctions). Observe complete cancellation (critical envelope = 0).
3. Change Junction ratio to 0 (completely asymmetric). The critical envelope becomes 1.0, meaning interference is incomplete.
4. Set Mean phase degrees to 90. Notice how the total current changes based on these parameters. The calculated total current will be 0.0 for this case, while the envelope is 1.0.