Qiskit code for QSVT example
This notebook shows how to generate data for the QSVT example using qiskit 1.2.4.
Here we provide the codes for block encoding the matrix \(A\), as well as the QSVT implementation. Qiskit does not have an adder by a constant function. Thus, we have modified their adder functions, which is applied between two quantum registers, to include this functionality.
# import time
# import numpy as np
# from qiskit.circuit import QuantumCircuit, QuantumRegister
# from qiskit.circuit.library import QFT
# from qiskit import QuantumCircuit, QuantumRegister, transpile
# from qiskit.circuit.library.standard_gates import XGate, RZGate
# BASIS_GATES = ["u", "cx"]
# OPT_LEVEL = 3
# class DraperQFTAdderConstant(QuantumCircuit):
# def __init__(self, num_state_qubits: int, constant: int, name: str = "DraperQFTAdderConst") -> None:
# # Create the quantum register
# qr_a = QuantumRegister(num_state_qubits, name="a")
# super().__init__(qr_a, name=name)
# # Apply the QFT
# self.append(QFT(num_state_qubits, do_swaps=False).to_gate(), qr_a)
# # Add the constant by applying controlled rotations
# for qubit in range(num_state_qubits):
# angle = (constant % (2 ** (qubit + 1))) * np.pi / (2 ** qubit)
# self.p(angle, qr_a[qubit])
# # Apply the inverse QFT
# self.append(QFT(num_state_qubits, do_swaps=False).inverse().to_gate(), qr_a)
# def get_reflect_around_zero(size):
# qc = QuantumCircuit(size)
# qc.x(0)
# qc.h(0)
# qc.mcx(control_qubits=[k for k in range(1,size)],ctrl_state="0"*(size-1),target_qubit=[0])
# qc.h(0)
# qc.x(0)
# return qc
# def get_cir_be(qc, data, block):
# qc.h(block[0])
# qc.h(block[2])
# qc.append(DraperQFTAdderConstant(num_state_qubits=len(data)+1,
# constant=2).control(1, ctrl_state=0).to_instruction(),[block[0]]+data[:]+[block[1]])
# qc.append(DraperQFTAdderConstant(num_state_qubits=len(data)+1,
# constant=-1+2**(len(data)+1)).to_instruction(),data[:]+[block[1]])
# qc.append(get_reflect_around_zero(len(data)).control(1, ctrl_state=0).to_instruction(),[block[2]]+data[:])
# qc.h(block[0])
# qc.h(block[2])
# return qc
# def apply_projector_controlled_phase(qc, phase, block_reg, aux_reg):
# qc.append(XGate().control(len(block_reg),ctrl_state=0),
# block_reg[:] + aux_reg[:]
# )
# qc.rz(phase, aux_reg)
# qc.append(XGate().control(len(block_reg),ctrl_state=0),
# block_reg[:] + aux_reg[:]
# )
# def apply_qsvt_step(qc, phase1, phase2, u, data, block, qsvt_aux):
# qc.append(u, data[:] + block[:])
# apply_projector_controlled_phase(qc, phase1, block, qsvt_aux)
# qc.append(u.inverse(), data[:] + block[:])
# apply_projector_controlled_phase(qc, phase2, block, qsvt_aux)
# def get_qsvt_circuit(qsvt_phases,
# size):
# block = QuantumRegister(3, 'block')
# data = QuantumRegister(size, 'data')
# qsvt_aux = QuantumRegister(1, 'qsvt_aux')
# cir_be = QuantumCircuit(data,block)
# cir_be = get_cir_be(cir_be,data, block)
# qsvt_cir = QuantumCircuit(data, block, qsvt_aux)
# qsvt_cir.h(qsvt_aux)
# apply_projector_controlled_phase(qsvt_cir, qsvt_phases[0], block, qsvt_aux)
# for i in range(int(np.floor((len(qsvt_phases) - 1) / 2))):
# apply_qsvt_step(qsvt_cir,
# qsvt_phases[(2 * i) + 1], qsvt_phases[(2 * i) + 2],
# cir_be,
# data,
# block,
# qsvt_aux
# )
# qsvt_cir.append(cir_be, data[:] + block[:])
# apply_projector_controlled_phase(qsvt_cir, qsvt_phases[len(qsvt_phases) - 1], block, qsvt_aux)
# qsvt_cir.h(qsvt_aux)
# return qsvt_cir
run an example
# SIZE = 6
# DEGREE = 3
# QSVT_PHASES = [1.280311896404252, 8.127145628464149, 1.8439603212845617, -5.002873410775335]
# start_time = time.time()
# qc_qsvt = get_qsvt_circuit(QSVT_PHASES, SIZE)
# transpiled_cir = transpile(
# qc_qsvt,
# basis_gates=BASIS_GATES,
# optimization_level=OPT_LEVEL,
# )
# transpilation_time = time.time()-start_time
# depth = transpiled_cir.depth()
# cx_counts = transpiled_cir.count_ops()["cx"]
# width = transpiled_cir.width()
# print(f"==== qiskit for {SIZE}==== time: {transpilation_time}")