Block Encoded Matrix is Permuted in Qiskit

Block Encoded Matrix is Permuted in Qiskit Ask Question Asked today Modified today Viewed 9 times 0 Trying to implement block encoding with LCU in Qiskit and the matrix looks correct but is permuted. What am I doing wrong ? from qiskit.quantum_info import SparsePauliOp, Statevector, Operator from qiskit import QuantumCircuit, transpile from qiskit.circuit.library import StatePreparation, PauliGate import numpy as np a = 0.25 b = 0.75 # matrix to be decomposed A = np.array( [[a, 0, 0, b], [0, -a, b, 0], [0, b, a, 0], [b, 0, 0, -a]] ) pauli_op = SparsePauliOp.from_operator(A) n_ancilla = int(np.ceil(np.log2(len(pauli_op.coeffs)))) n_reg = int(np.log2(len(A))) amps = np.sqrt(np.abs(pauli_op.coeffs) / np.linalg.norm(pauli_op.coeffs,ord=1)) padded_amps = np.zeros(2**n_ancilla) padded_amps[:len(amps)] = amps prep_gate = StatePreparation(padded_amps,label="Prep") qc = QuantumCircuit(n_ancilla + n_reg,n_ancilla) qc.append(prep_gate,qc.qubits[:n_ancilla]) for index, pauli in enumerate(pauli_op.paulis): intstr = f"{int(index):0{len(qc.qubits[:n_ancilla])}b}"[::-1] control_pauli_k = PauliGate(pauli.to_label()).control(num_ctrl_qubits=n_ancilla,ctrl_state=intstr) print(control_pauli_k) qc.append(control_pauli_k,qc.qubits) qc.append(prep_gate.inverse(),qc.qubits[:n_ancilla]) # qc.measure(qc.qubits[:n_ancilla],qc.clbits) qc.draw("mpl") Actual [[ 0.25, -0.43, 0. , 0. , 0. , 0. , 0.75, 0.43], [-0.43, 0.75, 0. , 0. , 0. , 0. , 0.43, 0.25], [ 0. , 0. , -0.25, 0.43, 0.75, 0.43, 0. , 0. ], [ 0. , 0. , 0.43, -0.75, 0.43, 0.25, 0. , 0. ], [ 0. , 0. , 0.75, 0.43, 0.25, -0.43, 0. , 0. ], [ 0. , 0. , 0.43, 0.25, -0.43, 0.75, 0. , 0. ], [ 0.75, 0.43, 0. , 0. , 0. , 0. , -0.25, 0.43], [ 0.43, 0.25, 0. , 0. , 0. , 0. , 0.43, -0.75]] Expected [[ 0.25 0. 0. 0.75 -0.43 0. 0. 0.43] [ 0. -0.25 0.75 0. 0. 0.43 0.43 0. ] [ 0. 0.75 0.25 0. 0. 0.43 -0.43 0. ] [ 0.75 0. 0. -0.25 0.43 0. 0. 0.43] [-0.43 0. 0. 0.43 0.75 0. 0. 0.25] [ 0. 0.43 0.43 0. 0. -0.75 0.25 0. ] [ 0. 0.43 -0.43 0. 0. 0.25 0.75 0. ] [ 0.43 0. 0. 0.43 0.25 0. 0. -0.75]] ``` qiskitquantum-stateunitaryblock-encoding Share Improve this question Follow asked 2 hours ago Raghav Baheti 1 New contributor 1 how did you come up with your "expected" matrix? First thing to check is usually the ordering of the tensor product: qiskit puts the "first" qubit last. So try changing all your basis elements from |abc⟩ | 𝑎 𝑏 𝑐 ⟩ to |cba⟩ | 𝑐 𝑏 𝑎 ⟩ . –  DaftWullie Commented 2 hours ago Add a comment Know someone who can answer? Share a link to this question via email, Twitter, or Facebook. Your Answer Sign up or log in Sign up using Google Sign up using Email and Password Post as a guest Name Email Required, but never shown Post Your Answer By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy. Start asking to get answers Find the answer to your question by asking. Ask question Explore related questions qiskitquantum-stateunitaryblock-encoding See similar questions with these tags. 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