Microwave Circulator (2D): Protecting a Qubit from Amplifier Back-Action

This 2D companion keeps the same three-port routing logic as the 3D circulator lab but lays it out as a flat schematic: qubit, circulator, amplifier and cold termination sit on a signal-flow diagram, with a probe pulse always running qubit → amplifier and an amplifier-noise pulse routed either to the termination (circulator in) or straight back to the qubit (bypassed). A noise-rate slider and a qubit-relaxation slider let you dial in how often back-action fires and how fast coherence recovers between hits, so the coherence and fidelity readouts respond to something you're actually driving rather than a fixed script.