Final answer:
Quantum Key Distribution utilizes the Heisenberg Uncertainty Principle to secure cryptographic keys. The attempt to intercept and measure the quantum-encoded information inevitably disturbs it, alerting the users to the presence of an eavesdropper. Protection is assured through the detection of anomalies introduced by any interception attempts.
Step-by-step explanation:
Quantum Key Distribution (QKD) is a method used to securely communicate a cryptographic key between two parties. It employs principles of quantum mechanics, particularly the Heisenberg Uncertainty Principle, to ensure the security of the key. The principle states that certain pairs of physical properties, like position and momentum, cannot be measured exactly at the same time, and measuring one property inevitably disturbs the other.
In QKD, when an eavesdropper tries to intercept the quantum states used to encode the key, the act of measuring these states necessarily disturbs them due to the quantum measurement. This disturbance can be detected by the legitimate communication parties, alerting them to the presence of an eavesdropper. Quantum tunneling and the interaction of light with matter, as seen in the photoelectric effect, are examples of these uniquely quantum phenomena affecting measurement outcomes.
The security of QKD parallels the physics behind quantum phenomena such as the pattern change when determining the path of an electron in the double-slit experiment and the quantum-tunneling observed in nuclear decay and semiconductors. These principles indicate that any attempt at interception introduces detectable anomalies, thereby revealing the presence of an eavesdropper. By checking a subset of the key for these anomalies, parties can be confident that the remainder of the key is secure if no disturbances are detected.