#### Q Full Adder

T
M
K
```"""
Build the quantum full adder (QFA) for any sum of
two quantum registers and one carry in. This circuit
is designed using the Qiskit framework. This
experiment run in IBM Q simulator with 1000 shots.
.
References:
"""

import math

import qiskit

input_1: int = 1, input_2: int = 1, carry_in: int = 1
) -> qiskit.result.counts.Counts:
"""
# >>> q_full_adder(inp_1, inp_2, cin)
# the inputs can be 0/1 for qubits in define
# values, or can be in a superposition of both
# states with hadamard gate using the input value 2.
# result for default values: {11: 1000}
qr_0: ──■────■──────────────■──
│  ┌─┴─┐          ┌─┴─┐
qr_1: ──■──┤ X ├──■────■──┤ X ├
│  └───┘  │  ┌─┴─┐└───┘
qr_2: ──┼─────────■──┤ X ├─────
┌─┴─┐     ┌─┴─┐└───┘
qr_3: ┤ X ├─────┤ X ├──────────
└───┘     └───┘
cr: 2/═════════════════════════
Args:
input_1: input 1 for the circuit.
input_2: input 2 for the circuit.
carry_in: carry in for the circuit.
Returns:
qiskit.result.counts.Counts: sum result counts.
>>> quantum_full_adder(1, 1, 1)
{'11': 1000}
>>> quantum_full_adder(0, 0, 1)
{'01': 1000}
>>> quantum_full_adder(1, 0, 1)
{'10': 1000}
>>> quantum_full_adder(1, -4, 1)
Traceback (most recent call last):
...
ValueError: inputs must be positive.
>>> quantum_full_adder('q', 0, 1)
Traceback (most recent call last):
...
TypeError: inputs must be integers.
>>> quantum_full_adder(0.5, 0, 1)
Traceback (most recent call last):
...
ValueError: inputs must be exact integers.
>>> quantum_full_adder(0, 1, 3)
Traceback (most recent call last):
...
ValueError: inputs must be less or equal to 2.
"""
if (
isinstance(input_1, str)
or isinstance(input_2, str)
or isinstance(carry_in, str)
):
raise TypeError("inputs must be integers.")

if (input_1 < 0) or (input_2 < 0) or (carry_in < 0):
raise ValueError("inputs must be positive.")

if (
(math.floor(input_1) != input_1)
or (math.floor(input_2) != input_2)
or (math.floor(carry_in) != carry_in)
):
raise ValueError("inputs must be exact integers.")

if (input_1 > 2) or (input_2 > 2) or (carry_in > 2):
raise ValueError("inputs must be less or equal to 2.")

# build registers
qr = qiskit.QuantumRegister(4, "qr")
cr = qiskit.ClassicalRegister(2, "cr")
# list the entries
entry = [input_1, input_2, carry_in]

quantum_circuit = qiskit.QuantumCircuit(qr, cr)

for i in range(0, 3):
if entry[i] == 2:
quantum_circuit.h(i)  # for hadamard entries
elif entry[i] == 1:
quantum_circuit.x(i)  # for 1 entries
elif entry[i] == 0:
quantum_circuit.i(i)  # for 0 entries

# build the circuit
quantum_circuit.ccx(0, 1, 3)  # ccx = toffoli gate
quantum_circuit.cx(0, 1)
quantum_circuit.ccx(1, 2, 3)
quantum_circuit.cx(1, 2)
quantum_circuit.cx(0, 1)

quantum_circuit.measure([2, 3], cr)  # measure the last two qbits

backend = qiskit.Aer.get_backend("aer_simulator")
job = qiskit.execute(quantum_circuit, backend, shots=1000)

return job.result().get_counts(quantum_circuit)

if __name__ == "__main__":
print(f"Total sum count for state is: {quantum_full_adder(1, 1, 1)}")
```