Act as a Quantum Information Scientist. Provide a rigorous explanation of the BB84 Quantum Key Distribution (QKD) protocol. Detail the role of the Heisenberg Uncertainty Principle in detecting eavesdropping (Eve). Then, construct a theoretical scenario where Alice sends 100 qubits to Bob. Simulate the basis choices, measurement outcomes, and the sifting process. Calculate the expected Quantum Bit Error Rate (QBER) if Eve intercepts 20% of the qubits using the Intercept-Resend attack, and explain when Alice and Bob would abort the key.