انتقل إلى المحتوى الرئيسي

حسابات المذيب الضمني باستخدام Qiskit Serverless

تقدير الاستخدام: دقيقتان على معالج Heron r2 (ملاحظة: هذا مجرد تقدير. قد يختلف وقت التشغيل الفعلي لديك.)

مخرجات التعلم

  • كيفية تهيئة وتشغيل سير عمل عن بُعد باستخدام Qiskit Serverless

  • كيفية حساب تأثيرات المذيب الضمني باستخدام حاسوب كمومي

المتطلبات المسبقة

الخلفية

تُستخدم حسابات المذيب الضمني بشكل متكرر في الفيزياء الحيوية الحاسوبية. تصف هذه النماذج كيفية تفاعل مركب مذاب مع مذيب، دون نمذجة نظام المذيب مباشرة. بدلاً من ذلك، يُوضع تقريب حيث يُغلف نموذج نظام المذاب في تمثيل رياضي لوسط عازل يُوصف تجريبياً. يتفاعل هذا التقريب العازل بعدها مع المذاب، الذي يُنمذج هو نفسه مباشرة. يؤثر الوسط العازل على خصائص نظام المذاب، مثل طاقة حالته الأرضية، من خلال التفاعل مع مجاله الإلكتروني. هذا مهم للنماذج الفيزيائية الحيوية المستخدمة، على سبيل المثال، في اكتشاف الأدوية، لأن المركبات تتصرف بشكل مختلف في بيئات عازلة مختلفة. نمذجة مركب في الهواء (في الفراغ) ستصف سلوكاً مختلفاً عن نمذجته في الماء. بما أن المركبات الصيدلانية يجب أن تدخل الجسم البشري، الذي يتكون هو نفسه في الغالب من الماء، فمن المفيد نمذجة مركب في محلول مثل الماء بدلاً من في الفراغ. مع نماذج المذيب الضمني، يمكننا تحقيق هذا السلوك بتكلفة زهيدة، رغم أن النتيجة النهائية ستكون بشكل عام أكثر تقريبية من النظير: نماذج المذيب الصريح الأكثر تكلفة حسابياً التي تُنشئ تمثيلات مباشرة لكل من جزيئات المذاب والمذيب.

في هذا البرنامج التعليمي، نوضح كيف يمكن دمج خوارزمية كمومية، التقطير الكمومي القائم على العينات (SQD)، في نموذج مذيب ضمني رخيص الحساب نسبياً. في المثال، نصف كيف يتصرف الميثيل أمين عند ذوبانه في الماء. نُقارن الخوارزمية الكمومية بطريقة مقارنة كلاسيكية حديثة تُسمى CASCI ونُظهر توافقاً وثيقاً بين هذه الحسابات. نعرض بنية حوسبة فائقة محورها الكم مصغرة، ننقل فيها المعالجة اللاحقة الكلاسيكية المكلفة حسابياً لجزء أخذ العينات الكمومي من الروتين إلى بيئة سحابية ضمن Qiskit Serverless. تُظهر الشيفرة أيضاً التوازي عبر أنوية المعالج المتاحة عن بُعد لتحسين وقت الحساب.

Qiskit Serverless هو إطار عمل لتشغيل أعباء عمل موزعة كمومية وكلاسيكية دون إدارة البنية التحتية. لا يوجد توفير خوادم (لا إنشاء EC2s، أو عناقيد، أو حاويات Docker)، ولا أدوات تنسيق (Kubernetes، Docker Swarm) ولا مراقبة/صيانة. تعمل كل مهمة Serverless في حاوية نظيفة، تُنفذ شيفرتك، ثم تُغلق. لا توجد ذاكرة بين المهام. تكتب شيفرتك ببساطة ثم تُرسل مهمتك. ضمن مهمة Serverless، يمكن لبرنامج الوصول بسلاسة إلى واجهات IBM Quantum® الخلفية ومعالجة النتائج كلاسيكياً هناك. مع Qiskit Serverless، يمكن للمستخدمين الوصول إلى أنوية معالج وذاكرة عن بُعد تعمل دائماً، مما يوفر توزيع أعباء عمل كلاسيكية معينة عبر موارد بعيدة. يكسب المستخدمون أيضاً بعض المزايا في المعالجة المتوازية للبرامج مع تجنب الصداع الشائع من إغلاق الجهاز في منتصف التنفيذ. لمزيد من المعلومات حول Qiskit Serverless، انظر توثيقه، بالإضافة إلى مواد إضافية على GitHub.

يُظهر هذا البرنامج التعليمي تطبيقاً ذا صلة لما يلي:

  • التقطير الكمومي القائم على العينات

  • نماذج الحوسبة العميل-الخادم للحوسبة الكمومية

استُلهم هذا البرنامج التعليمي واستند إلى بحث أُجري في Cleveland Clinic، كما هو موصوف في Kaliakin, Danil, et al. "Implicit solvent sample-based quantum diagonalization." The Journal of Physical Chemistry B 129.23 (2025): 5788-5796، الذي يعرض سير العمل الكامل لحسابات المذيب الضمني ويوسعه بخاصية التناسق الذاتي التكراري للمذيب («خوارزمية Heartwood»، M. Motta، T. Pellegrini، 2025)، وتحسين الهندسة، والاختيار التلقائي لتخطيط الكيوبت. يُرجى الرجوع إلى قالب وظيفة SQD IEF-PCM من Qiskit، المُطوّر بشكل مشترك بين Cleveland Clinic وIBM® استناداً إلى بحث Cleveland Clinic، للحصول على واجهة مبسطة وجاهزة لتشغيل حسابات المذيب الضمني.

المتطلبات

قبل بدء هذا البرنامج التعليمي، تأكد من تثبيت ما يلي:

  • Qiskit SDK v2.0 أو أحدث مع دعم التصور
  • Qiskit Runtime v0.40 أو أحدث (pip install qiskit-ibm-runtime)
  • Qiskit IBM Catalog pip install qiskit_ibm_catalog
  • Qiskit IBM Serverless pip install qiskit_serverless
  • إضافة Qiskit: التقطير الكمومي القائم على العينات (SQD) v0.12.0 pip install qiskit_addon_sqd
  • PySCF pip install pyscf
  • FFSIM pip install ffsim
  • Matplotlib pip install matplotlib
  • Geometric pip install geometric

الإعداد

# Added by doQumentation — required packages for this notebook
!pip install -q ffsim matplotlib numpy psutil pyscf qiskit qiskit-addon-sqd qiskit-ibm-catalog qiskit-ibm-runtime qiskit-serverless rustworkx
# Establish Quantum Resource connection
from qiskit_ibm_runtime import QiskitRuntimeService

service = QiskitRuntimeService()

backend = service.least_busy()
print(f"Using backend {backend.name}")
# Establish Classical HPC Resource connection
from qiskit_ibm_catalog import QiskitFunction, QiskitServerless

client = QiskitServerless()

أنشئ دليلاً بجانب البرنامج التفاعلي الرئيسي مباشرة يُسمى source_files. ستضع ملفات Python في هذا الدليل تنوي مشاركتها مع بيئة الحوسبة البعيدة. يجب أن تُنشئ ملفين:

  • source_files\diagonalization_engine.py

  • source_files\classical_simulation.py

انقر لتوسيع النص لكل نص برمجي أدناه، ثم انسخ المحتوى والصقه في ملف محلي بأسماء المسارات هذه.

انقر لعرض source_files\diagonalization_engine.py
انقر لعرض source_files\classical_simulation.py
ملاحظة

لمزيد من المعلومات، يرجى الاطلاع على دليل قالب دالة SQD IEF-PCM Qiskit (المُطوَّر بالاشتراك بين Cleveland Clinic وIBM) المُشار إليه أعلاه. راجع أيضًا مكتبة qiskit_addon_sqd.

#!/usr/bin/env python3
import numpy as np
from json.encoder import JSONEncoder
from json.decoder import JSONDecoder
from functools import partial
import os

from qiskit_serverless import (
distribute_task,
get_arguments,
get,
save_result,
get_runtime_service,
)
from qiskit_addon_sqd.fermion import (
SCIResult,
diagonalize_fermionic_hamiltonian,
solve_sci,
)

### Argument retrieval
args = get_arguments()

data = args["data"] # Chemistry Data
energy_tol = args["energy_tol"] # SQD option
occupancies_tol = args["occupancies_tol"] # SQD option
max_iterations = args["max_iterations"] # SQD option
symmetrize_spin = args["symmetrize_spin"] # Eigenstate solver option
carryover_threshold = args["carryover_threshold"] # Eigenstate solver option
num_batches = args["num_batches"] # Eigenstate solver option
samples_per_batch = args["samples_per_batch"] # Eigenstate solver option
max_cycle = args["max_cycle"] # Eigenstate solver option
mem = args["mem"] # Memory per Worker

# --- fan‑out target: 1 CPU + mem GB RAM per call -------------
@distribute_task(target={"cpu": 1, "mem": mem * 1024**3})
def _solve_sci_worker(
ix, ci_strs, one_body_tensor, two_body_tensor, norb, nelec, spin_sq
):
print(f">>>>> WORKER {ix} INITIATED")
res = solve_sci(
ci_strs,
one_body_tensor,
two_body_tensor,
norb=norb,
nelec=nelec,
spin_sq=spin_sq,
)

print(f">>>>> WORKER {ix} COMPLETE")
return res

def distribute_solve_sci_batch(
ci_strings: list[tuple[np.ndarray, np.ndarray]],
one_body_tensor: np.ndarray,
two_body_tensor: np.ndarray,
norb: int,
nelec: tuple[int, int],
*,
spin_sq: float | None = None,
**kwargs,
) -> list[SCIResult]:
"""Diagonalize Hamiltonian in subspaces, parallelizing across
vCPUs in the Serverless environment.

Args:
ci_strings: List of pairs (strings_a, strings_b) of arrays of
spin-alpha CI strings and spin-beta CI strings whose Cartesian
product gives the basis of the subspace in which to perform a
diagonalization.
one_body_tensor: The one-body tensor of the Hamiltonian.
two_body_tensor: The two-body tensor of the Hamiltonian.
norb: The number of spatial orbitals.
nelec: The numbers of alpha and beta electrons.
spin_sq: Target value for the total spin squared for the ground state.
If ``None``, no spin will be imposed.
**kwargs: Keyword arguments to pass to
`pyscf.fci.selected_ci.kernel_fixed_space`
(https://pyscf.org/pyscf_api_docs/pyscf.fci.html#pyscf.fci.selected_ci.kernel_fixed_space

Returns:
The results of the diagonalizations in the subspaces given by ci_strings.
"""
inputs = [
(ix, ci_strs, one_body_tensor, two_body_tensor, norb, nelec, spin_sq)
for ix, ci_strs in enumerate(ci_strings)
]

# fan‑out: spawn one worker per input tuple
print(">>>>> ENTERING WORKER FAN-OUT")
refs = [_solve_sci_worker(*input_) for input_ in inputs]
print(">>>>> WAITING ON WORKERS TO FINISH TASKS")

# fan‑in: block until every worker finishes
results = get(refs)
print(">>>>> DISTRIBUTED JOBS COMPLETED")

return results

# A caveat of executing a Python program remotely is
# that the inputs to the remote program must be passed
# over an internet network. Similarly, the outputs
# must be passed back to the local program via the same
# structure. Python objects are not always able to be
# passed over a network, and must be encoded in a
# JSON serializable format.
i_data = JSONDecoder().decode(data)

# i_data has all of the information needed from the
# local program to pick up where the computation left off
# after its submission to the remote environment.
[
job_id,
hcore,
eri,
num_orbitals,
nuclear_repulsion_energy,
num_elec_a,
num_elec_b,
] = i_data

# Re-convert data back into numpy format, after serialization
hcore = np.array(hcore)
eri = np.array(eri)
nuclear_repulsion_energy = np.float64(nuclear_repulsion_energy)

# Instantiate Runtime Service to retrieve the
# bitstrings from the QPU job. We provided these
# credentials upon Serverless setup.
service = get_runtime_service()

# retrieving the QPU job data from the Serverless side
job = service.job(job_id)
primitive_result = job.result()
pub_result = primitive_result[0]
bit_array = pub_result.data.meas # Getting the bitstrings

# Pass options to the built-in eigensolver
sci_solver = partial(
distribute_solve_sci_batch, spin_sq=0.0, max_cycle=max_cycle
)

# List to capture intermediate results
result_history = []

def callback(results: list[SCIResult]):
result_history.append(results)
iteration = len(result_history)
print(f">>>>> SQD ITERATION {iteration}")
for i, result in enumerate(results):
print(f">>>>> SUBSAMPLE {i}")
print(f">>>>> \tENERGY: {result.energy + nuclear_repulsion_energy}")
print(
f">>>>> \tSUBSPACE DIMENSION: {np.prod(result.sci_state.amplitudes.shape)}"
)

result = diagonalize_fermionic_hamiltonian(
hcore,
eri,
bit_array,
samples_per_batch=samples_per_batch,
norb=num_orbitals,
nelec=(num_elec_a, num_elec_b),
num_batches=num_batches,
energy_tol=energy_tol,
occupancies_tol=occupancies_tol,
max_iterations=max_iterations,
sci_solver=sci_solver,
symmetrize_spin=symmetrize_spin,
carryover_threshold=carryover_threshold,
callback=callback,
seed=12345,
)

print(">>>>> EXACT DIAGONALIZATION COMPLETE. CLEANING UP, SERIALIZING DATA.")
# Numpy arrays are not JSON serializable.
# Convert them to List objects before using the JSONEncoder
o_data = JSONEncoder().encode(
[
result.energy + nuclear_repulsion_energy,
result.energy,
result.rdm1.tolist(),
result.rdm2.tolist(),
[x.tolist() for x in result.orbital_occupancies],
[
result.sci_state.nelec,
result.sci_state.norb,
[x.tolist() for x in result.sci_state.orbital_occupancies()],
[x.tolist() for x in result.sci_state.rdm()],
],
]
)

# JSON-safe package
save_result({"outputs": o_data}) # single JSON blob returned to client
#!/usr/bin/env python3
from json.encoder import JSONEncoder
from json.decoder import JSONDecoder

from qiskit_serverless import get_arguments, save_result

import pyscf
from pyscf import gto, scf
from pyscf.solvent import pcm
from pyscf.mcscf import avas

import psutil

mem_info = (
psutil.virtual_memory()
) # Get information about virtual memory (RAM)
total_ram_gb = mem_info.total / (1024**3) # Convert bytes to GB
print(f">>>>> SERVERLESS TOTAL RAM: {total_ram_gb:.2f} GB")

### Argument retrieval
args = get_arguments()
data = args["data"] # Chemistry Data

i_data = JSONDecoder().decode(data)
[mol_geo, eps, ao_labels] = i_data

print(">>>>> DEFINING MOLECULE")
mol = gto.M()
mol.atom = mol_geo
mol.basis = "cc-pVDZ"
mol.unit = "Ang"
mol.charge = 0
mol.spin = 0
mol.verbose = 0

print(">>>>> BUILDING MOLECULE")
mol.build()

print(">>>>> DEFINING PCM")
cm = pcm.PCM(mol)
cm.eps = eps # for water
cm.method = "IEF-PCM"

print(">>>>> BUILDING RESTRICTED HARTREE FOCK")
mf = scf.RHF(mol).PCM(cm) # This is the Final SCF object
mf.kernel(verbose=0)

print(">>>>> RUNNING AVAS")
avas_ = avas.AVAS(mf, ao_labels, with_iao=True, canonicalize=True, verbose=0)
avas_.kernel()
norb, ne_act, mo_avas = avas_.ncas, avas_.nelecas, avas_.mo_coeff

print(">>>>> STARTING CASCI")
mc_pcm = pyscf.mcscf.CASCI(mf, norb, ne_act).PCM(
cm
) # Make sure to decorate the CASCI object with PCM
mc_pcm.mo_coeff = mo_avas
# mc_pcm.max_memory = 140000

(CASCI_E, _, _, _, _) = mc_pcm.kernel(verbose=0)

print(f">>>>> CASCI_E: {CASCI_E}")
o_data = JSONEncoder().encode([float(CASCI_E)])

# JSON-safe package
save_result({"outputs": o_data}) # single JSON blob returned to client

نحتاج إلى مشاركة البرنامج المُراد تشغيله في بيئة السحابة، وإعادة تحميله في أي وقت نُغيّر فيه شيفرته المصدرية:

client.upload(
QiskitFunction(
title="diagonalization_engine",
entrypoint="diagonalization_engine.py", # lives in ./source_files
working_dir="source_files",
)
)
client.upload(
QiskitFunction(
title="classical_simulation",
entrypoint="classical_simulation.py", # lives in ./source_files
working_dir="source_files",
)
)

مثال محاكي صغير المقياس

لا يستخدم هذا البرنامج التعليمي محاكياً صغير المقياس لأن الهدف هو إظهار تطبيق كمومي قابل للتوسع يتجاوز نطاق استكشاف المحاكي. بدلاً من ذلك، نُظهر لاحقاً كيف يمكن تنفيذ هذه الطريقة باستخدام طريقة مقارنة كلاسيكية حديثة تُسمى CASCI.

مثال جهاز كبير المقياس

# This is a useful helper function that displays
# remote job execution details to the user's local machine
def feedback_serverless(serverless_job):
import time

# Wait for the job to execute
print(f">>>>> Serverless status: {serverless_job.job_id}")
timer = 0
while timer < 10000:
if (
serverless_job.status() == "QUEUED"
or serverless_job.status() == "INITIALIZING"
or serverless_job.status() == "RUNNING"
):
print(f">>>>> [{timer}s] Serverless job {serverless_job.job_id}: \
{serverless_job.status()}")
time.sleep(10)
timer += 10

elif serverless_job.status() == "ERROR":
print(
f">>>>> Serverless job {serverless_job.job_id}: {serverless_job.status()}"
)
print(">>>>> Logs:")
print(serverless_job.logs())
break

elif serverless_job.status() == "DONE":
print(
f">>>>> Serverless job {serverless_job.job_id}: {serverless_job.status()}"
)
break

else:
break

return

الخطوة 1: تحويل المدخلات الكلاسيكية إلى مسألة كمومية

1.1: تهيئة كائن الجزيء باستخدام هندسة جزيئية معروفة a priori\textit{a priori}

# Reference guide for building molecule structures:
# https://pyscf.org/user/gto.html
# Video tutorial on building molecular objects in PySCF:
# https://www.youtube.com/watch?v=cNC2cY9E9j0

molecule_name = "Methylamine"

methylamine_geo = """
N -0.7154 0.0000 0.0000;
C 0.7154 0.0000 0.0000;
H 1.1069 0.0916 1.0174;
H 1.0996 0.8349 -0.5930;
H 1.0996 -0.9274 -0.4345;
H -1.0625 0.8564 0.4294;
H -1.0625 -0.7661 0.5753;
"""
# Imports
import pyscf
from pyscf import gto # Deals with molecular initialization
from pyscf import scf # Solvation methods

# Explicitly defining the Methylamine molecule
mol = gto.M()
mol.atom = methylamine_geo
mol.basis = "cc-pVDZ"
mol.unit = "Ang"
mol.charge = 0
mol.spin = 0
mol.verbose = 0

mol.build()

1.2: تعريف تأثيرات الإذابة باستخدام نموذج الوسط المتصل القابل للاستقطاب (PCM)

# You can explore other solvents (such as methanol) by
# retrieving other dielectric parameters from:
# https://gaussian.com/scrf/
from pyscf.solvent import pcm

eps_water = 78.3553 # If solvating in a different medium,
# set this constant appropriately using a known value
cm = pcm.PCM(mol)
cm.eps = eps_water # PySCF defaults to water solvation,
# but here we show this solvation parameter explicitly

cm.method = (
"IEF-PCM" # Alternative solvation models include C-PCM, SS(V)PE, COSMO
)
# Create a "Restricted Hartree-Fock" object for the solute,
# then wrap the SCF object with a Polarizable Continuum Model
mf_pcm0 = scf.RHF(mol).PCM(
cm
) # Restricted Hartree-Fock misses instantaneous correlations,
# post-HF methods like CCSD, CI, MP2 might be worth exploring

1.3: تحسين الهندسة باستخدام TRIC

# Geometry optimization with geomeTRIC
from pyscf.geomopt.geometric_solver import (
optimize,
) # GeomeTRIC under the hood, for geometry optimization

mol_opt = optimize(
mf_pcm0, tol_grad=3e-4, verbose=0
) # Use geomeTRIC/TRIC under the hood

1.4: تحضير نموذج الوسط المتصل وكائن المجال المتوسط بالمتغيرات ذات الصلة

from pyscf.mcscf import avas

# Re-define PCM
cm = pcm.PCM(mol_opt)
cm.eps = eps_water # for water
cm.method = "IEF-PCM"

# Re-build Restricted Hartree Fock object
mf_opt = scf.RHF(mol_opt).PCM(cm)
mf_opt.kernel(verbose=0)

# Run AVAS
ao_labels = ["C 2s", "C 2p", "N 2s", "N 2p", "H 1s"]
avas_ = avas.AVAS(
mf_opt, ao_labels, with_iao=True, canonicalize=True, verbose=0
)
avas_.kernel()
norb, ne_act, mo_avas = avas_.ncas, avas_.nelecas, avas_.mo_coeff

num_elec_a = (ne_act + mol_opt.spin) // 2
num_elec_b = (ne_act - mol_opt.spin) // 2

الخطوة 2: تحسين المسألة لتنفيذها على الأجهزة الكمومية

لمزيد من المعلومات حول الدوال المساعدة الموضحة هنا، انظر البرنامج التعليمي التقطير الكمومي القائم على العينات لهاميلتوني كيميائي.

# Standard SQD helper functions (From SQD Tutorial)

from typing import Sequence
import rustworkx
from qiskit.providers import BackendV2
from qiskit import QuantumCircuit, QuantumRegister

from rustworkx import NoEdgeBetweenNodes, PyGraph

IBM_TWO_Q_GATES = {"cx", "ecr", "cz"}

def create_linear_chains(num_orbitals: int) -> PyGraph:
"""In zig-zag layout, there are two linear chains (with connecting
qubits between the chains). This function creates those two linear
chains: a rustworkx PyGraph with two disconnected linear chains.
Each chain contains `num_orbitals` number of nodes, that is, in the
final graph there are `2 * num_orbitals` number of nodes.

Args:
num_orbitals (int): Number orbitals or nodes in each linear chain.
They are also known as alpha-alpha interaction qubits.

Returns:
A rustworkx.PyGraph with two disconnected linear chains each with
`num_orbitals` number of nodes.
"""
G = rustworkx.PyGraph()

for n in range(num_orbitals):
G.add_node(n)

for n in range(num_orbitals - 1):
G.add_edge(n, n + 1, None)

for n in range(num_orbitals, 2 * num_orbitals):
G.add_node(n)

for n in range(num_orbitals, 2 * num_orbitals - 1):
G.add_edge(n, n + 1, None)

return G

def create_lucj_zigzag_layout(
num_orbitals: int, backend_coupling_graph: PyGraph
) -> tuple[PyGraph, int]:
"""This function creates the complete zigzag graph that 'can be mapped'
to an IBM QPU with heavy-hex connectivity (the zigzag must be an
isomorphic sub-graph to the QPU/backend coupling graph for it to be
mapped). The zigzag pattern includes both linear chains (alpha-alpha
interactions) and connecting qubits between the linear chains
(alpha-beta interactions).

Args:
num_orbitals (int): Number of orbitals, that is, number of nodes in
each alpha-alpha linear chain.
backend_coupling_graph (PyGraph): The coupling graph of the backend
on which the LUCJ ansatz will be mapped and run. This function takes
the coupling graph as a undirected `rustworkx.PyGraph` where there
is only one 'undirected' edge between two nodes, that is, qubits.
Usually, the coupling graph of an IBM backend is directed (for
example, Eagle devices such as ibm_brisbane) or may have two edges
between two nodes (for example, Heron `ibm_torino`). A user
needs to make such graphs undirected or remove duplicate edges
(or do both) to make them compatible with this function.

Returns:
G_new (PyGraph): The graph with IBM backend compliant zigzag pattern.
num_alpha_beta_qubits (int): Number of connecting qubits between the
linear chains in the zigzag pattern. While we want as many
connecting (alpha-beta) qubits between the linear (alpha-alpha)
chains, we cannot accommodate all due to qubit and connectivity
constraints of backends. This is the maximum number of connecting
qubits the zigzag pattern can have while being backend compliant
(that is, isomorphic to backend coupling graph).
"""
isomorphic = False
G = create_linear_chains(num_orbitals=num_orbitals)

num_iters = num_orbitals
while not isomorphic:
G_new = G.copy()
num_alpha_beta_qubits = 0
for n in range(num_iters):
if n % 4 == 0:
new_node = 2 * num_orbitals + num_alpha_beta_qubits
G_new.add_node(new_node)
G_new.add_edge(n, new_node, None)
G_new.add_edge(new_node, n + num_orbitals, None)
num_alpha_beta_qubits = num_alpha_beta_qubits + 1
isomorphic = rustworkx.is_subgraph_isomorphic(
backend_coupling_graph, G_new
)
num_iters -= 1

return G_new, num_alpha_beta_qubits

def lightweight_layout_error_scoring(
backend: BackendV2,
virtual_edges: Sequence[Sequence[int]],
physical_layouts: Sequence[int],
two_q_gate_name: str,
) -> list[list[list[int], float]]:
"""Lightweight and heuristic function to score isomorphic layouts. There
can be many zigzag patterns, each with different set of physical qubits,
that can be mapped to a backend. Some of them might include fewer noise
qubits and couplings than others. This function computes a simple error
score for each such layout. It sums up 2Q gate error for all couplings
in the zigzag pattern (layout) and measurement of errors of physical
qubits in the layout to compute the error score.

Note:
This lightweight scoring can be refined using concepts such as
mapomatic.

Args:
backend (BackendV2): A backend.
virtual_edges (Sequence[Sequence[int]]): Edges in the device-
compliant zigzag pattern where nodes are numbered from 0 to (2 *
num_orbitals + num_alpha_beta_qubits).
physical_layouts (Sequence[int]): All physical layouts of the zigzag
pattern that are isomorphic to each other and to the larger backend
coupling map.
two_q_gate_name (str): The name of the two-qubit gate of the
backend. The name is used for fetching two-qubit gate error from
backend properties.

Returns:
scores (list): A list of lists where each sublist contains two
items. First item is the layout, and second item is a float
representing error score of the layout. The layouts in the `scores`
are sorted in the ascending order of error score.
"""
props = backend.properties()
scores = []
for layout in physical_layouts:
total_2q_error = 0
for edge in virtual_edges:
physical_edge = (layout[edge[0]], layout[edge[1]])
try:
ge = props.gate_error(two_q_gate_name, physical_edge)
except Exception:
ge = props.gate_error(two_q_gate_name, physical_edge[::-1])
total_2q_error += ge
total_measurement_error = 0
for qubit in layout:
meas_error = props.readout_error(qubit)
total_measurement_error += meas_error
scores.append([layout, total_2q_error + total_measurement_error])
return sorted(scores, key=lambda x: x[1])

def _make_backend_cmap_pygraph(backend: BackendV2) -> PyGraph:
graph = backend.coupling_map.graph
if not graph.is_symmetric():
graph.make_symmetric()
backend_coupling_graph = graph.to_undirected()

edge_list = backend_coupling_graph.edge_list()
removed_edge = []
for edge in edge_list:
if set(edge) in removed_edge:
continue
try:
backend_coupling_graph.remove_edge(edge[0], edge[1])
removed_edge.append(set(edge))
except NoEdgeBetweenNodes:
pass

return backend_coupling_graph

def get_zigzag_physical_layout(
num_orbitals: int, backend: BackendV2, score_layouts: bool = True
) -> tuple[list[int], int]:
"""The main function that generates the zigzag pattern
with physical qubits that can be used as an `intial_layout` in a
preset passmanager/transpiler.

Args:
num_orbitals (int): Number of orbitals.
backend (BackendV2): A backend.
score_layouts (bool): Optional. If `True`, it uses the
`lightweight_layout_error_scoring` function to score the
isomorphic layouts and returns the layout with
fewer erroneous qubits.
If `False`, returns the first isomorphic subgraph.

Returns:
A tuple of device compliant layout (list[int]) with zigzag pattern
and an int representing number of alpha-beta-interactions.
"""
backend_coupling_graph = _make_backend_cmap_pygraph(backend=backend)

G, num_alpha_beta_qubits = create_lucj_zigzag_layout(
num_orbitals=num_orbitals,
backend_coupling_graph=backend_coupling_graph,
)

isomorphic_mappings = rustworkx.vf2_mapping(
backend_coupling_graph, G, subgraph=True
)
isomorphic_mappings = list(isomorphic_mappings)

edges = list(G.edge_list())

layouts = []
for mapping in isomorphic_mappings:
initial_layout = [None] * (2 * num_orbitals + num_alpha_beta_qubits)
for key, value in mapping.items():
initial_layout[value] = key
layouts.append(initial_layout)

two_q_gate_name = IBM_TWO_Q_GATES.intersection(
backend.configuration().basis_gates
).pop()

if score_layouts:
scores = lightweight_layout_error_scoring(
backend=backend,
virtual_edges=edges,
physical_layouts=layouts,
two_q_gate_name=two_q_gate_name,
)

return scores[0][0][:-num_alpha_beta_qubits], num_alpha_beta_qubits

return layouts[0][:-num_alpha_beta_qubits], num_alpha_beta_qubits
from qiskit.transpiler import generate_preset_pass_manager
import ffsim

# Initial LUCJ ansatz layout
initial_layout, _ = get_zigzag_physical_layout(norb, backend=backend)

# Initialize a pass manager
pass_manager = generate_preset_pass_manager(
optimization_level=3, backend=backend, initial_layout=initial_layout
)

pass_manager.pre_init = ffsim.qiskit.PRE_INIT

الخطوتان 3 و4: التنفيذ باستخدام Qiskit والمعالجة اللاحقة باستخدام Qiskit Serverless

هنا، نجمع بين الخطوة 3 (التنفيذ) والخطوة 4 (المعالجة اللاحقة) لأن سياق تطبيق نموذج المذيب الضمني يتطلب حلقة تغذية راجعة تكرارية تُنفذ عدة دورات من التنفيذ والمعالجة اللاحقة لتحسين الحساب النهائي.

3.1 حساب طاقة هارتري-فوك المقيدة

# Run the kernel to get the RHF energy
mf_opt = scf.RHF(mol_opt).PCM(cm)
hf_e = float(mf_opt.kernel())
print(f"Restricted Hartree-Fock Energy: {hf_e}")

3.2: إنشاء طاقة مرجعية كلاسيكية باستخدام CASCI

# Setup a Serverless Client
worker = client.load("classical_simulation")
from json.encoder import JSONEncoder

ao_labels = ["C 2s", "C 2p", "N 2s", "N 2p", "H 1s"]
data_e = JSONEncoder().encode([mol_opt.tostring(), eps_water, ao_labels])
serverless_job = worker.run(data=data_e)
# Optionally, check the Serverless status feedback
# Don't sit here and stare at the feedback unless debugging.
# You can go develop something else while the Serverless job runs.
_ = feedback_serverless(serverless_job)
# If you make a mistake and need to cancel something

# for job in client.jobs():
# job.cancel()
from json.decoder import JSONDecoder

CASCI_E = JSONDecoder().decode(serverless_job.result()["outputs"])[0]
# We have approximated the red, classical baseline from
# Figure 1 for Methanol (North-West panel)
print(f"CASCI/IEF-PCM(cc-pVDZ): E={CASCI_E}")

تكوين معاملات التطبيق

# Systematically vary these parameters to improve hardware results

# Set to "True" to run on real hardware
use_hardware = True

# Error suppression/mitigation options
# >> Configure within Sampler primitive

# Transpiler Options
optimization_level = 3

# Heartwood algorithm options
n_iter = 15 # How many update loops to run
resample = 1 # (resample=1 -> resample the QPU after every
# update loop; resample=n_iter -> sample QPU only once)
shots = 10000

# SQD options
energy_tol = 1e-4
occupancies_tol = 1e-3
max_iterations = 12

# Eigenstate solver options
num_batches = 5
samples_per_batch = 300
symmetrize_spin = True
carryover_threshold = 1e-5
max_cycle = 200

# Classical post-processing options
local = (
False # Remote, Serverless (False) versus Local Post-Processing (True)
)
mem = 16 # Memory allocated to each diagonalization worker (Gb)
# Heartwood algorithm subroutines
import numpy as np
import pyscf
from pyscf import ao2mo, cc
from functools import reduce
import ffsim

from json.encoder import JSONEncoder
from json.decoder import JSONDecoder
import time

from functools import partial
from qiskit_addon_sqd.fermion import (
SCIResult,
diagonalize_fermionic_hamiltonian,
solve_sci_batch,
)

def update_rdm(casci_object, dmas):
"""
Inputs:
mc -> CASCI object
dmas -> Spin-summed 1-particle reduced density matrix

This function returns the CASCI/SQD one-body density matrix in
the full basis of atomic orbitals, written as the sum (last line)
of two terms:
- a contribution from the core orbitals,
np.dot(mocore, mocore.conj().T) * 2, (core = inactive and doubly-occupied)
- a contribution from the active-space orbitals and electrons (dmas)
rotated from the active-space to the AO basis (the reduce operation)

Outputs:
rho_approximation: The CASCI/SQD one-body density matrix
in the full basis of atomic orbitals

"""
mo_coeff = casci_object.mo_coeff
ncore = casci_object.ncore
ncas = casci_object.ncas
mocore = mo_coeff[:, :ncore]
mocas = mo_coeff[:, ncore : ncore + ncas]
dm1 = np.dot(mocore, mocore.conj().T) * 2

rho_approximation = dm1 + reduce(np.dot, (mocas, dmas, mocas.conj().T))
return rho_approximation

def run_active_space_calculation(
h1e_cas, h2e_cas, norb, ne_act, orbs, fermilevel, ecore
):
# ----- perform an HF and a CCSD calculation in the active space
from pyscf import tools
from datetime import datetime

now = datetime.now().strftime("%H:%M:%S")
print(">>>>> ACTIVE SPACE CALCULATIONS ")
tools.fcidump.from_integrals(
f"as_fcidump_{now}.txt",
h1e_cas,
h2e_cas,
norb,
ne_act,
ms=0,
nuc=ecore,
) # Forcefully represents the active space in the correct structure
mf_as = tools.fcidump.to_scf(f"as_fcidump_{now}.txt")
os.remove(f"as_fcidump_{now}.txt")
mf_as.kernel()
print(">>>>> RUNNING CCSD")

mf_cc = cc.CCSD(mf_as)
mf_cc.kernel()
orbts = mf_as.mo_coeff
t1, t2 = mf_cc.t1, mf_cc.t2
print(">>>>> UPDATED t1, t2 PARAMETERS")

# ----- update the HF orbitals
active = list(
range(fermilevel - ne_act // 2, fermilevel - ne_act // 2 + norb)
)
orbs[:, active] = np.dot(orbs[:, active], orbts)
return orbs, t1, t2

def get_lucj(norb, num_elec_a, num_elec_b, t1, t2, n_reps=1):
print(">>>>> CONSTRUCTING LUCJ CIRCUIT")

alpha_alpha_indices = [(p, p + 1) for p in range(norb - 1)]
alpha_beta_indices = [(p, p) for p in range(0, norb, 4)]

ucj_op = ffsim.UCJOpSpinBalanced.from_t_amplitudes(
t1=t1, # <---- Update t1 each loop
t2=t2, # <---- Update t2 each loop
n_reps=n_reps,
interaction_pairs=(alpha_alpha_indices, alpha_beta_indices),
)
nelec = (num_elec_a, num_elec_b)

# create an empty quantum circuit
qubits = QuantumRegister(2 * norb, name="q")
circuit = QuantumCircuit(qubits)

# prepare Hartree-Fock state as the reference state
# and append it to the quantum circuit
circuit.append(ffsim.qiskit.PrepareHartreeFockJW(norb, nelec), qubits)

# apply the UCJ operator to the reference state
circuit.append(ffsim.qiskit.UCJOpSpinBalancedJW(ucj_op), qubits)
circuit.measure_all()

return circuit

# Classical diagonalization engine sent to HPC
def classically_diagonalize(
bit_array=None, # Bit string array (only needed if locally processing data)
nuclear_repulsion_energy=None, # Electronic energy from the core orbitals
hcore=None, # 1-electron hamiltonian integrals
eri=None, # 2-electron hamiltonian integrals
num_orbitals=None, # Number of spatial orbitals
nelec=None, # Number of electrons
num_elec_a=None, # Alpha orbitals
num_elec_b=None, # Beta orbitals
job_id=None, # QPU bitstring Job ID
client=None, # Diagonalization engine worker
energy_tol=1e-4, # SQD option
occupancies_tol=1e-3, # SQD option
max_iterations=12, # SQD option
num_batches=8, # Eigenstate solver option
samples_per_batch=300, # Eigenstate solver option
symmetrize_spin=False, # Eigenstate solver option
carryover_threshold=1e-5, # Eigenstate solver option
max_cycle=200, # Eigenstate solver option
local=True, # Remote vs Local Diagonalization
mem=16.0, # Memory per Serverless Worker (Gb)
):
print(">>>>> STARTING DIAGONALIZATION ENGINE ")
# Pass options to the built-in eigensolver. If you just want to use
# the defaults, you can omit this step, in which case you would not
# specify the sci_solver argument in the call to
# diagonalize_fermionic_hamiltonian below.
if local:
sci_solver = partial(
solve_sci_batch, spin_sq=0.0, max_cycle=max_cycle
)

# List to capture intermediate results
result_history = []

def callback(results: list[SCIResult]):
result_history.append(results)
iteration = len(result_history)
print(f">>>>> SQD ITERATION {iteration}")
for i, result in enumerate(results):
print(f">>>>> SUBSAMPLE {i}")
print(
f">>>>> \tENERGY: {result.energy + nuclear_repulsion_energy}"
)
print(
f">>>>> \tSUBSPACE DIMENSION: {np.prod(result.sci_state.amplitudes.shape)}"
)

result = diagonalize_fermionic_hamiltonian(
hcore,
eri,
bit_array,
samples_per_batch=samples_per_batch,
norb=num_orbitals,
nelec=(nelec // 2, nelec // 2),
num_batches=num_batches,
energy_tol=energy_tol,
occupancies_tol=occupancies_tol,
max_iterations=max_iterations,
sci_solver=sci_solver,
symmetrize_spin=symmetrize_spin,
carryover_threshold=carryover_threshold,
callback=callback,
seed=12345,
)

result = (result.energy, result.rdm1, result.rdm2)

else:
# Serverless Logic
print(
f">>>>> SENDING QISKIT RUNTIME JOB {job_id} TO QISKIT SERVERLESS"
)

data = [
job_id,
hcore.tolist(),
eri.tolist(),
int(num_orbitals),
float(nuclear_repulsion_energy),
int(num_elec_a),
int(num_elec_b),
]

# Encode the execution dependencies with the JSONEncoder
data_e = JSONEncoder().encode(data)

# Send to Serverless
worker = client.load("diagonalization_engine")
serverless_job = worker.run(
data=data_e,
energy_tol=energy_tol, # SQD option
occupancies_tol=occupancies_tol, # SQD option
max_iterations=max_iterations, # SQD option
symmetrize_spin=symmetrize_spin, # Eigenstate solver option
carryover_threshold=carryover_threshold, # Eigenstate solver option
num_batches=num_batches, # Eigenstate solver option
samples_per_batch=samples_per_batch, # Eigenstate solver option
max_cycle=max_cycle, # Eigenstate solver option
mem=mem, # Memory per Worker (Gb)
)

# Wait for the job to execute
_ = feedback_serverless(serverless_job)

o_data = JSONDecoder().decode(serverless_job.result()["outputs"])
result = (o_data[1], np.array(o_data[2]), np.array(o_data[3]))

print(f">>>>>>>>>> Active Space Energy: {o_data[1]}")
print(f">>>>>>>>>> rdm1: {o_data[2]}")
print(f">>>>>>>>>> rdm2: {o_data[3]}")

return result
# The Heartwood algorithm
import numpy as np

from qiskit_ibm_runtime import SamplerV2 as Sampler
from qiskit_addon_sqd.counts import generate_bit_array_uniform

mc = pyscf.mcscf.CASCI(mf_opt, ncas=norb, nelecas=ne_act).PCM(cm)
mc.with_solvent.method = mf_opt.with_solvent.method # Here we make sure
# that mc is also using the same solvent method defined earlier (IEF-PCM)
mc.with_solvent.eps = mf_opt.with_solvent.eps # Set the dielectric parameters
mc.mo_coeff = mo_avas.copy() # Update the molecular orbitals to include
# those computed in the presence of the solvent

h1e_cas, ecore = (
mc.get_h1eff()
) # <-- h1eff is the 1-electron hamiltonian integrals. h1e_cas is
# a common alias. ecore is the electronic energy from the core orbitals.
h2e_cas = ao2mo.restore(
1, mc.get_h2eff(), norb
) # <-- get the 2-electron hamiltonian integrals

mc.mo_coeff, t1, t2 = run_active_space_calculation(
h1e_cas,
h2e_cas,
norb,
ne_act,
mo_avas.copy(),
mf_opt.mol.nelectron // 2,
ecore,
)

# Sampler primitive options
sampler = Sampler(mode=backend)

# Explore error suppression techniques and see if they can improve result quality
sampler.options.dynamical_decoupling.enable = True
sampler.options.dynamical_decoupling.sequence_type = "XY4"
sampler.options.twirling.enable_measure = True
sampler.options.environment.job_tags = ["TUT_ISC"]
# sampler.options.twirling.enable_gates = False
# sampler.options.twirling.num_randomizations = 10
# sampler.options.twirling.shots_per_randomization = 1024

# initial approximation for rdm1
with_solvent_e, with_solvent_v = None, None # Don't touch
data = []
for iiter in range(n_iter):
print(f">>>>> IMPLICIT SOLVENT ITERATION {iiter+1}/{n_iter}")
if with_solvent_v is not None:
# Subsequent update loops enter here
mc.get_hcore = lambda *args: mc._scf.get_hcore() + with_solvent_v
else:
# First update loop starts here
# hcore is the CAS space (classically computed) 1-electron
# hamiltonian, which we default to at the start of the routine.
mc.get_hcore = (
lambda *args: mc._scf.get_hcore()
) # REF: https://pyscf.org/pyscf_api_docs/pyscf.mcscf.html#pyscf.scf.hf.CASBase.get_h1cas

# Alias mapping
# hcore : h1e_cas : h1e_eff
# nuclear_repulsion_energy : ecore
# eri : h2e_cas : h2e_eff

h1e_cas, ecore = (
mc.get_h1eff()
) # <-- h1eff is the 1-electron hamiltonian integrals. h1e_cas is a
# common alias. ecore is the electronic energy from the core orbitals.
h2e_cas = ao2mo.restore(
1, mc.get_h2eff(), norb
) # <-- get the 2-electron hamiltonian integrals

mc.mo_coeff, t1, t2 = run_active_space_calculation(
h1e_cas,
h2e_cas,
norb,
ne_act,
mo_avas.copy(),
mf_opt.mol.nelectron // 2,
ecore,
)

if use_hardware:
if (
iiter % resample == 0
): # <-- Toggle how often you refresh your bitstrings here. The
# developer suggests that you do it every time, but benevolently
# provides the freedom to disagree with him via the resample
# control variable.
# The "Quantum-Centric" part
print(">>>>> GENERATING BITSTRINGS USING QUANTUM HARDWARE")
# LUCJ Ansatz construction
circuit = get_lucj(norb, num_elec_a, num_elec_b, t1, t2, n_reps=1)

print(f">>>>> TRANSPILING LUCJ TO {backend.name}")
isa_circuit = pass_manager.run(circuit)
print(f">>>>> SUBMITTING ISA_CIRCUIT TO {backend.name}")
job = sampler.run(
[isa_circuit], shots=shots
) # <----- Error Suppression/Mitigation configured performed upstream
job_id = str(job.job_id())

timer = 0
while job.status() != "DONE":
timer += 10
print(
f">>>>> [{timer}s] RUNTIME JOB {job_id}: {job.status()}"
)
time.sleep(10)

primitive_result = job.result()
print(f">>>>> RETRIEVED {job_id} FROM {backend.name}")

pub_result = primitive_result[0]
bit_array = pub_result.data.meas

else:
print(">>>>> GENERATING BITSTRINGS CLASSICALLY")
rng = np.random.default_rng(24)
bit_array = generate_bit_array_uniform(
100_000, 2 * norb, rand_seed=rng
) # <-- Sample bitstrings from a uniform distribution. This is
# useful for debug, but runs out of steam on large systems
job_id = float(
"nan"
) # <-- we will check that valid job_id's were passed during grading
local = True

# The "Classical Post-processing" part
result = classically_diagonalize(
bit_array=bit_array,
nuclear_repulsion_energy=ecore, # Electronic energy from the core orbitals
hcore=h1e_cas, # 1-electron hamiltonian integrals
eri=h2e_cas, # 2-electron hamiltonian integrals
num_orbitals=norb, # Number of spatial orbitals
nelec=ne_act, # Number of electrons
num_elec_a=ne_act // 2, # Alpha orbitals
num_elec_b=ne_act // 2, # Beta orbitals
job_id=job_id, # QPU bitstring Job ID
client=client, # Diagonalization engine worker
energy_tol=energy_tol, # SQD option
occupancies_tol=occupancies_tol, # SQD option
max_iterations=max_iterations, # SQD option
num_batches=num_batches, # Eigenstate solver option
samples_per_batch=samples_per_batch, # Eigenstate solver option
symmetrize_spin=symmetrize_spin, # Eigenstate solver option
carryover_threshold=carryover_threshold, # Eigenstate solver option
max_cycle=max_cycle, # Eigenstate solver option
local=local, # Remote vs Local Diagonalization
mem=mem, # Memory per Worker (Gb)
)

# e : SQD-based estimate of the energy
# rdm1: Spin-summed 1-particle reduced density matrix
e, rdm1 = result[0], result[1]
rho_approximation = update_rdm(
mc, rdm1
).copy() # <--- Reconstruct the one-body density matrix in the
# atomic orbital basis to update the external potential due to
# the solvent

if with_solvent_e is not None:
# Subsequent update loops enter here
edup = np.einsum(
"ij,ji->", with_solvent_v, rho_approximation
) # <-- edup: Incrementing the energy calculation with
# subsequent iterations
e += ecore + with_solvent_e - edup

else:
# First update loop enters here
e += (
ecore # Pulled from the CAS space object (molecule's core energy)
)

# Outputs:
# with_solvent_e : scalar energy correction due to solvent polarization
# with_solvent_v : Fock-like matrix to be added to the core Hamiltonian in SCF
with_solvent_e, with_solvent_v = mc.with_solvent._get_vind(
rho_approximation
)
data.append((iiter, float(e), job_id))
print(f">>>>> END IITER {iiter}")
print(f">>>>> TOTAL ENERGY: {e}\n")
import matplotlib.pyplot as plt
from matplotlib.ticker import ScalarFormatter

def plot_data(data, baseline=0, name=None, save=False):
x_vals, y_vals, job_ids = zip(*data)
fig, ax = plt.subplots(figsize=(10, 6))

# Plot line + markers
ax.plot(
x_vals,
y_vals,
color="navy",
linewidth=2,
marker="o",
markersize=5,
label="Energy trajectory",
)
ax.axhline(
baseline,
color="red",
linestyle="--",
linewidth=1.5,
label="Reference energy",
)

# Force plain formatting
ax.yaxis.set_major_formatter(ScalarFormatter(useMathText=True))
ax.ticklabel_format(style="plain", axis="y")

# Annotate each point with its exact value
for x, y, job_id in zip(x_vals, y_vals, job_ids):
ax.annotate(
f"{y:.8f}, ID: {job_id}",
(x, y),
textcoords="offset points",
xytext=(0, 8), # vertical offset
ha="center",
fontsize=8,
rotation=25,
color="navy",
)

# Annotate the Classical Reference line
for x, y in zip([0.5], [baseline]):
ax.annotate(
f"{y:.5f}",
(x, y),
textcoords="offset points",
xytext=(0, 8), # vertical offset
ha="center",
fontsize=8,
rotation=25,
color="red",
)

# Titles, labels, etc
ax.set_title(
f"SQD/IEF-PCM(cc-pVDZ) - {name}\nEnergy Convergence",
fontsize=14,
fontweight="bold",
pad=15,
)
ax.set_xlabel("Update Iterations", fontsize=12)
ax.set_ylabel("Total Energy (Hartrees)", fontsize=12)
ax.grid(True, linestyle="--", linewidth=0.6, alpha=0.7)
ax.legend(frameon=True, loc="best")
plt.tight_layout()

if save:
plt.savefig(f"./results/{name}_energy_convergence.png")
return fig, ax
# Plot your data

fig, ax = plot_data(data, baseline=CASCI_E, name=molecule_name, save=True)
plt.show()

الخطوات التالية

توصيات

إذا وجدت هذا العمل مثيراً للاهتمام، فقد تكون مهتماً بالموارد التالية: