Quantum Echo Keys Theory: Secure Key Generation Using Echoed Superposition's in Feedback Quantum Circuits

This work proposes Quantum Echo Keys Theory (QEK-T), a cryptographic framework in which quantum keys are generated using echoed superposition’s inside feedback-controlled quantum circuits. The protocol distributes key information across temporal measurement echoes rather than storing it in a single quantum state. Qiskit simulations on a four-qubit system demonstrate perfect recovery in ideal conditions and high resilience under realistic noise. Parametric noise sweeps confirm graceful fidelity degradation, establishing temporal echo correlation as a new security dimension in quantum cryptography.