diff --git a/quantum/ripple_adder_classic.py b/quantum/ripple_adder_classic.py new file mode 100644 index 000000000..f5b0a980c --- /dev/null +++ b/quantum/ripple_adder_classic.py @@ -0,0 +1,108 @@ +# https://github.com/rupansh/QuantumComputing/blob/master/rippleadd.py +# https://en.wikipedia.org/wiki/Adder_(electronics)#Full_adder +# https://en.wikipedia.org/wiki/Controlled_NOT_gate + +from qiskit import Aer, QuantumCircuit, execute +from qiskit.providers import BaseBackend + + +def store_two_classics(val1: int, val2: int) -> (QuantumCircuit, str, str): + """ + Generates a Quantum Circuit which stores two classical integers + Returns the circuit and binary representation of the integers + """ + x, y = bin(val1)[2:], bin(val2)[2:] # Remove leading '0b' + + # Ensure that both strings are of the same length + if len(x) > len(y): + y = y.zfill(len(x)) + else: + x = x.zfill(len(y)) + + # We need (3 * number of bits in the larger number)+1 qBits + # The second parameter is the number of classical registers, to measure the result + circuit = QuantumCircuit((len(x) * 3) + 1, len(x) + 1) + + # We are essentially "not-ing" the bits that are 1 + # Reversed because its easier to perform ops on more significant bits + for i in range(len(x)): + if x[::-1][i] == "1": + circuit.x(i) + for j in range(len(y)): + if y[::-1][j] == "1": + circuit.x(len(x) + j) + + return circuit, x, y + + +def full_adder( + circuit: QuantumCircuit, + input1_loc: int, + input2_loc: int, + carry_in: int, + carry_out: int, +): + """ + Quantum Equivalent of a Full Adder Circuit + CX/CCX is like 2-way/3-way XOR + """ + circuit.ccx(input1_loc, input2_loc, carry_out) + circuit.cx(input1_loc, input2_loc) + circuit.ccx(input2_loc, carry_in, carry_out) + circuit.cx(input2_loc, carry_in) + circuit.cx(input1_loc, input2_loc) + + +def ripple_adder( + val1: int, val2: int, backend: BaseBackend = Aer.get_backend("qasm_simulator") +) -> int: + """ + Quantum Equivalent of a Ripple Adder Circuit + Uses qasm_simulator backend by default + + Currently only adds 'emulated' Classical Bits + but nothing prevents us from doing this with hadamard'd bits :) + + Only supports adding +ve Integers + + >>> ripple_adder(3, 4) + 7 + >>> ripple_adder(10, 4) + 14 + >>> ripple_adder(-1, 10) + Traceback (most recent call last): + ... + ValueError: Both Integers must be positive! + """ + + if val1 < 0 or val2 < 0: + raise ValueError("Both Integers must be positive!") + + # Store the Integers + circuit, x, y = store_two_classics(val1, val2) + + """ + We are essentially using each bit of x & y respectively as full_adder's input + the carry_input is used from the previous circuit (for circuit num > 1) + + the carry_out is just below carry_input because + it will be essentially the carry_input for the next full_adder + """ + for i in range(len(x)): + full_adder(circuit, i, len(x) + i, len(x) + len(y) + i, len(x) + len(y) + i + 1) + circuit.barrier() # Optional, just for aesthetics + + # Measure the resultant qBits + for i in range(len(x) + 1): + circuit.measure([(len(x) * 2) + i], [i]) + + res = execute(circuit, backend, shots=1).result() + + # The result is in binary. Convert it back to int + return int(list(res.get_counts().keys())[0], 2) + + +if __name__ == "__main__": + import doctest + + doctest.testmod()