def qubit_send_w_retransmission(host, q_size, receiver_id,
checksum_size_per_qubit):
"""
Sends the data qubits along with checksum qubits , with the possibility of retransmission.
:param host: Sender of qubits
:param q_size: Number of qubits to be sent
:param receiver_id: ID of the receiver
:param checksum_size_per_qubit: Checksum qubit per data qubit size
:return:
"""
bit_arr = np.random.randint(2, size=q_size)
print('Bit array to be sent: ' + str(bit_arr))
qubits = []
for i in range(q_size):
q_tmp = Qubit(host)
if bit_arr[i] == 1:
q_tmp.X()
qubits.append(q_tmp)
check_qubits = host.add_checksum(qubits, checksum_size_per_qubit)
checksum_size = int(q_size / checksum_size_per_qubit)
qubits.append(check_qubits)
checksum_cnt = 0
for i in range(q_size + checksum_size):
if i < q_size:
q = qubits[i]
else:
q = qubits[q_size][checksum_cnt]
checksum_cnt = checksum_cnt + 1
q_success = False
got_ack = False
number_of_retransmissions = 0
while not got_ack and number_of_retransmissions < MAX_NUM_OF_TRANSMISSIONS:
print('Alice prepares qubit')
err_1 = Qubit(host)
# encode logical qubit
q.cnot(err_1)
_, ack_received = host.send_qubit(receiver_id, q, await_ack=True)
if ack_received:
err_1.release()
got_ack = True
q_success = True
if not q_success:
print('Alice: Bob did not receive the qubit')
# re-introduce a qubit to the system and correct the error
q = Qubit(host)
err_1.cnot(q)
number_of_retransmissions += 1
if number_of_retransmissions == 10:
print("Alice: too many attempts made")
return False
return True
def RepeaterProtocol(host, alice, bob):
timeout = 180
start = time.time()
logrepeater = open("logs/repeater.txt", "w")
bit_count = 0
while bit_count < 1:
if time.time() - start > timeout:
return
host.empty_classical()
time.sleep(1)
# Synchronize with Alice and Bob
host.send_broadcast(str(bit_count))
wait = True
messages = []
while wait:
messages = host.classical
if len(messages) == 2:
wait = False
host.empty_classical()
basis = random.randint(0, 1)
ack_arrived = host.send_classical(alice, basis, await_ack = True)
if not ack_arrived:
logrepeater.write("Repeater: Failed to send basis %d to Alice\n"%bit_count)
print("Repeater: Failed to send basis %d to Alice"%bit_count)
continue
ack_arrived = host.send_classical(bob, basis, await_ack = True)
if not ack_arrived:
logrepeater.write("Repeater: Failed to send basis %d to Bob\n"%bit_count)
print("Repeater: Failed to send basis %d to Bob"%bit_count)
continue
# Generate two qubits
q_alice = Qubit(host)
q_mem_alice = Qubit(host)
# Entangle the two qubits to create an entangled pair
q_alice.H()
q_alice.cnot(q_mem_alice)
# Send one of the qubits of the entangled state to Alice
q_alice_id, ack_arrived = host.send_qubit(alice, q_alice, await_ack=True)
if not ack_arrived:
# Alice did not receive qubit
logrepeater.write("Repeater: Alice did not receive EPR %d\n"%bit_count)
print("Repeater: Alice did not receive EPR %d"%bit_count)
#q_alice.measure()
q_mem_alice.measure()
continue
else:
alice_bit = host.get_next_classical(alice, wait=5)
if alice_bit is not None:
logrepeater.write("Repeater: Alice received entangled qubit %d and measured %s\n"%(bit_count, str(alice_bit.content)))
print("Repeater: Alice received entangled qubit %d and measured %s"%(bit_count, str(alice_bit.content)))
else:
continue
# Generate two qubits
q_bob = Qubit(host)
q_mem_bob = Qubit(host)
# Entangle the two qubits to create an entangled pair
q_bob.H()
q_bob.cnot(q_mem_bob)
q_bob_id, ack_arrived = host.send_qubit(bob, q_bob, await_ack=True)
if not ack_arrived:
# Bob did not receive qubit
#print("Repeater: Bob did not receive EPR")
logrepeater.write("Repeater: Bob did not receive EPR %d\n"%bit_count)
print("Repeater: Bob did not receive EPR %d"%bit_count)
#q_bob.measure()
q_mem_bob.measure()
q_mem_alice.measure()
continue
else:
bob_bit = host.get_next_classical(bob, wait=5)
if bob_bit is not None:
logrepeater.write("Repeater: Bob received entangled qubit %d and measured %s\n"%(bit_count, str(bob_bit.content)))
print("Repeater: Bob received entangled qubit %d and measured %s"%(bit_count, str(bob_bit.content)))
else:
continue
# Both Alice and Bob have successfully made BB84 measurements
# Perform Bell state measurement on the two qubits present in the memory
q_mem_alice.cnot(q_mem_bob)
q_mem_alice.H()
alice_bit = q_mem_alice.measure()
bob_bit = q_mem_bob.measure()
# Send results of measurement to Bob
ack_arrived = host.send_classical(bob, "%d:%d"%(alice_bit, bob_bit), await_ack = True)
if not ack_arrived:
logrepeater.write("Repeater: Bell State Measurement %d void\n"%bit_count)
print("Repeater: Bell State Measurement %d void"%bit_count)
q_mem_alice.release()
q_mem_bob.release()
continue
else:
# Communicate Bob's success to Alice
ack_arrived = host.send_classical(alice, str(bit_count), await_ack=True)
if not ack_arrived:
print("Repeater: Alice did not acknowledge Bob's success for bit %d"%bit_count)
logrepeater.write("Repeater: Alice did not acknowledge Bob's success for bit %d\n"%bit_count)
continue
bit_count += 1
logrepeater.close()