Secure communication protocols are becoming increasingly important, e.g. for internet-based
communication. Quantum key distribution (QKD) allows two parties, commonly called Alice and Bob, to
generate a secret sequence of 0s and 1s called a key that is only known to themselves. Classically,
Alice and Bob could never be certain that their communication was not compromised by a malicious
eavesdropper. Quantum mechanics however makes secure communication possible. The fundamental
principle of quantum mechanics that taking a measurement perturbs the system (unless the measurement
is compatible with the quantum state) also applies to an eavesdropper. Using appropriate protocols
to create the key, Alice and Bob can detect the presence of an eavesdropper by errors in their
measurements. As part of the QuVis Quantum Mechanics Visualisation Project, we have developed a
suite of four interactive simulations that demonstrate the basic principles of three different QKD
protocols. The simula…