Source code for mitiq.pt.pt

# Copyright (C) Unitary Fund
#
# This source code is licensed under the GPL license (v3) found in the
# LICENSE file in the root directory of this source tree.

import random
from typing import List

import cirq

from mitiq import QPROGRAM
from mitiq.interface import accept_qprogram_and_validate

# P, Q, R, S from https://arxiv.org/pdf/2301.02690.pdf
CNOT_twirling_gates = [
    (cirq.I, cirq.I, cirq.I, cirq.I),
    (cirq.I, cirq.X, cirq.I, cirq.X),
    (cirq.I, cirq.Y, cirq.Z, cirq.Y),
    (cirq.I, cirq.Z, cirq.Z, cirq.Z),
    (cirq.Y, cirq.I, cirq.Y, cirq.X),
    (cirq.Y, cirq.X, cirq.Y, cirq.I),
    (cirq.Y, cirq.Y, cirq.X, cirq.Z),
    (cirq.Y, cirq.Z, cirq.X, cirq.Y),
    (cirq.X, cirq.I, cirq.X, cirq.X),
    (cirq.X, cirq.X, cirq.X, cirq.I),
    (cirq.X, cirq.Y, cirq.Y, cirq.Z),
    (cirq.X, cirq.Z, cirq.Y, cirq.Y),
    (cirq.Z, cirq.I, cirq.Z, cirq.I),
    (cirq.Z, cirq.X, cirq.Z, cirq.X),
    (cirq.Z, cirq.Y, cirq.I, cirq.Y),
    (cirq.Z, cirq.Z, cirq.I, cirq.Z),
]
CZ_twirling_gates = [
    (cirq.I, cirq.I, cirq.I, cirq.I),
    (cirq.I, cirq.X, cirq.Z, cirq.X),
    (cirq.I, cirq.Y, cirq.Z, cirq.Y),
    (cirq.I, cirq.Z, cirq.I, cirq.Z),
    (cirq.X, cirq.I, cirq.X, cirq.Z),
    (cirq.X, cirq.X, cirq.Y, cirq.Y),
    (cirq.X, cirq.Y, cirq.Y, cirq.X),
    (cirq.X, cirq.Z, cirq.X, cirq.I),
    (cirq.Y, cirq.I, cirq.Y, cirq.Z),
    (cirq.Y, cirq.X, cirq.X, cirq.Y),
    (cirq.Y, cirq.Y, cirq.X, cirq.X),
    (cirq.Y, cirq.Z, cirq.Y, cirq.I),
    (cirq.Z, cirq.I, cirq.Z, cirq.I),
    (cirq.Z, cirq.X, cirq.I, cirq.X),
    (cirq.Z, cirq.Y, cirq.I, cirq.Y),
    (cirq.Z, cirq.Z, cirq.Z, cirq.Z),
]


[docs] def pauli_twirl_circuit( circuit: QPROGRAM, num_circuits: int = 10, ) -> List[QPROGRAM]: r"""Return the Pauli twirled versions of the input circuit. Only the $\mathrm{CZ}$ and $\mathrm{CNOT}$ gates in an input circuit are Pauli twirled as specified in :cite:`Saki_2023_arxiv`. Args: circuit: The input circuit to execute with twirling. num_circuits: Number of circuits to be twirled, and averaged. Returns: The expectation value estimated with Pauli twirling. """ CNOT_twirled_circuits = twirl_CNOT_gates(circuit, num_circuits) twirled_circuits = [ twirl_CZ_gates(c, num_circuits=1)[0] for c in CNOT_twirled_circuits ] return twirled_circuits
[docs] def twirl_CNOT_gates(circuit: QPROGRAM, num_circuits: int) -> List[QPROGRAM]: """Generate a list of circuits using Pauli twirling on CNOT gates. Args: circuit: The circuit to generate twirled versions of num_circuits: The number of sampled circuits to return """ return [_twirl_CNOT_qprogram(circuit) for _ in range(num_circuits)]
@accept_qprogram_and_validate def _twirl_CNOT_qprogram(circuit: cirq.Circuit) -> cirq.Circuit: return circuit.map_operations(_twirl_single_CNOT_gate)
[docs] def twirl_CZ_gates(circuit: QPROGRAM, num_circuits: int) -> List[QPROGRAM]: """Generate a list of circuits using Pauli twirling on CZ gates. Args: circuit: The circuit to generate twirled versions of num_circuits: The number of sampled circuits to return """ return [_twirl_CZ_qprogram(circuit) for _ in range(num_circuits)]
@accept_qprogram_and_validate def _twirl_CZ_qprogram(circuit: cirq.Circuit) -> cirq.Circuit: return circuit.map_operations(_twirl_single_CZ_gate) def _twirl_single_CNOT_gate(op: cirq.Operation) -> cirq.OP_TREE: """Function which converts a CNOT gate to a logical equivalent. That is, it converts CNOT operations into the following, leaving all other cirq operations alone. --P---⏺---R-- | --Q---⊕---S-- Where P, Q, R, and S are Pauli operators sampled so as to not effect change on the underlying unitary. """ if op.gate != cirq.CNOT: return op P, Q, R, S = random.choice(CNOT_twirling_gates) control_qubit, target_qubit = op.qubits return [ P.on(control_qubit), Q.on(target_qubit), op, R.on(control_qubit), S.on(target_qubit), ] def _twirl_single_CZ_gate(op: cirq.Operation) -> cirq.OP_TREE: """Function which converts a CZ gate to a logical equivalent. That is, it converts CZ operations into the following, leaving all other cirq operations alone. --P---⏺---R-- | --Q---⏺---S-- Where P, Q, R, and S are Pauli operators sampled so as to not effect change on the underlying unitary. """ if op.gate != cirq.CZ: return op P, Q, R, S = random.choice(CZ_twirling_gates) control_qubit, target_qubit = op.qubits return [ P.on(control_qubit), Q.on(target_qubit), op, R.on(control_qubit), S.on(target_qubit), ]