QuantumSpy.py

from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister, Aer

from QuantumPlatform import QuantumPlatform


# Set up the program
def get_quantum_spy_circuit():
    alice = QuantumRegister(1, name='alice')
    fiber = QuantumRegister(1, name='fiber')
    bob   = QuantumRegister(1, name='bob')
    alice_had = ClassicalRegister(1, name='ahad')
    alice_val = ClassicalRegister(1, name='aval')
    fiber_val = ClassicalRegister(1, name='fval')
    bob_had   = ClassicalRegister(1, name='bhad')
    bob_val   = ClassicalRegister(1, name='bval')
    qc = QuantumCircuit(alice, fiber, bob, alice_had, alice_val, fiber_val, bob_had, bob_val)

# Use Alice's QPU to generate two random bits
    qc.reset(alice)          # write the value 0
    qc.h(alice)
    qc.measure(alice, alice_had)
    qc.reset(alice)          # write the value 0
    qc.h(alice)
    qc.measure(alice, alice_val)

# Prepare Alice's qubit
    qc.reset(alice)          # write the value 0
    qc.x(alice).c_if(alice_val, 1)
    qc.h(alice).c_if(alice_had, 1)

# Send the qubit!
    qc.swap(alice, fiber)

# Activate the spy
    spy_is_present = True
    if spy_is_present:
        qc.barrier()
        spy_had = True
        if spy_had:
            qc.h(fiber)
        qc.measure(fiber, fiber_val)
        qc.reset(fiber)
        qc.x(fiber).c_if(fiber_val, 1)
        if spy_had:
            qc.h(fiber)

    qc.barrier()

# Use Bob's QPU to generate a random bit
    qc.reset(bob)
    qc.h(bob)
    qc.measure(bob, bob_had)

# Receive the qubit!
    qc.swap(fiber, bob)
    qc.h(bob).c_if(bob_had, 1)
    qc.measure(bob, bob_val)

    return qc


def main():
    qc = get_quantum_spy_circuit()

    platform_backend = QuantumPlatform(Aer, 'statevector_simulator')
    job = platform_backend.schedule_job(qc)
    result = job.result()

# Now Alice emails Bob to tell
# him her had setting and value.
# If the had setting matches and the
# value does not, there's a spy!
    counts = result.get_counts(qc)
    print('counts:',counts)
    caught = False
    for key,val in counts.items():
        ahad,aval,f,bhad,bval = (int(x) for x in key.split(' '))
        if ahad == bhad:
            if aval != bval:
                print('Caught a spy!')
                caught = True
    if not caught:
        print('No spies detected.')

    outputstate = result.get_statevector(qc, decimals=3)
    print(outputstate)
#    qc.draw()        # draw the circuit


main()