Qiskit code for the BB84 algorithm

Our BB84 simulation is a 150-line program (give or take a few lines). To make the program comprehensible, we’ll divide it into 16 function definitions. Let’s start with the imports and constant declarations:

import randomfrom qiskit import QuantumCircuit, QuantumRegister, \
    ClassicalRegister, Aer, execute
NUMBER_OF_CIRCUITS = 100
DOES_EVE_EXIST = False
CHECK_MARK = u'\u2713'

According to these declarations, we’ll be creating 100 circuits – one for each of the qubits that Alice sends to Bob. We’ll simulate a situation in which no eavesdropper exists. For convenience, we will declare CHECK_MARK to be the Unicode symbol.

The main flow of execution looks like this:

circuits = create_circuits(NUMBER_OF_CIRCUITS,                           DOES_EVE_EXIST...