qkd.py

#!/bin/env python
# -*- coding: utf-8 -*-
##
# qkd.py: Defines functions needed to perform a basic quantum key exchange
#     protocol.
##
# Copyright (c) Sarah Kaiser and Chris Granade.
# Code sample from the book "Learn Quantum Computing with Python and Q#" by
# Sarah Kaiser and Chris Granade, published by Manning Publications Co.
# Book ISBN 9781617296130.
# Code licensed under the MIT License.
##

from interface import QuantumDevice, Qubit

def prepare_classical_message(bit: bool, q: Qubit) -> None:
    if bit:
        q.x()

def eve_measure(q: Qubit) -> bool:
    return q.measure()

def send_classical_bit(device: QuantumDevice, bit: bool) -> None:
    with device.using_qubit() as q:
        prepare_classical_message(bit, q)
        result = eve_measure(q)
        q.reset()
    assert result is bit


def qrng(device: QuantumDevice) -> bool:
    with device.using_qubit() as q:
        q.h()
        return q.measure()

def prepare_classical_message_plusminus(bit: bool, q: Qubit) -> None:
    if bit:
        q.x()
    q.h()

def eve_measure_plusminus(q: Qubit) -> bool:
    q.h()
    return q.measure()

def send_classical_bit_plusminus(device: QuantumDevice, bit: bool) -> None:
    with device.using_qubit() as q:
        prepare_classical_message_plusminus(bit, q)
        result = eve_measure_plusminus(q)
        assert result is bit

def send_classical_bit_wrong_basis(device: QuantumDevice, bit: bool) -> None:
    with device.using_qubit() as q:
        prepare_classical_message(bit, q)
        result = eve_measure_plusminus(q)
        assert result is bit, "Two parties do not have the same bit value"