DraperQFTAdder

class qiskit.circuit.library.DraperQFTAdder(num_state_qubits, kind='fixed', name='DraperQFTAdder')

Bases: Adder

A circuit that uses QFT to perform in-place addition on two qubit registers.

For registers with $n$ qubits, the QFT adder can perform addition modulo $2^n$ (with kind="fixed") or ordinary addition by adding a carry qubits (with kind="half").

As an example, a non-fixed_point QFT adder circuit that performs addition on two 2-qubit sized registers is as follows:

 a_0:   ─────────■──────■────────────────────────■────────────────
                 │      │                        │
 a_1:   ─────────┼──────┼────────■──────■────────┼────────────────
        ┌──────┐ │P(π)  │        │      │        │       ┌───────┐
 b_0:   ┤0     ├─■──────┼────────┼──────┼────────┼───────┤0      ├
        │      │        │P(π/2)  │P(π)  │        │       │       │
 b_1:   ┤1 qft ├────────■────────■──────┼────────┼───────┤1 iqft ├
        │      │                        │P(π/2)  │P(π/4) │       │
cout_0: ┤2     ├────────────────────────■────────■───────┤2      ├
        └──────┘                                         └───────┘

References:

[1] T. G. Draper, Addition on a Quantum Computer, 2000. arXiv:quant-ph/0008033

[2] Ruiz-Perez et al., Quantum arithmetic with the Quantum Fourier Transform, 2017. arXiv:1411.5949

[3] Vedral et al., Quantum Networks for Elementary Arithmetic Operations, 1995. arXiv:quant-ph/9511018

Parameters

• num_state_qubits (int) – The number of qubits in either input register for state $|a\rangle$ or $|b\rangle$. The two input registers must have the same number of qubits.
• kind (str) – The kind of adder, can be 'half' for a half adder or 'fixed' for a fixed-sized adder. A half adder contains a carry-out to represent the most-significant bit, but the fixed-sized adder doesn’t and hence performs addition modulo 2 ** num_state_qubits.
• name (str) – The name of the circuit object.

Raises

ValueError – If num_state_qubits is lower than 1.

Attributes

name

from qiskit import QuantumCircuit
 
qc = QuantumCircuit(2, 2, name="my_circuit")
print(qc.name)

my_circuit