Overview

Each entry gives the arguments, defaults, return value and errors of a call, or the fields of a record with their meaning and unit. The quickstart and the guides show the same calls in context.

Import the Problems and the workflow calls from nwqlib, and the Methods from nwqlib.algorithms. This example finds the smaller eigenvalue of [[2, 1], [1, 2]], whose eigenvalues are 1 and 3:

from nwqlib import Eigenproblem, solve
from nwqlib.algorithms import Lanczos

problem = Eigenproblem(A=[[2.0, 1.0], [1.0, 2.0]])
method = Lanczos(initial_state=[1, 0], krylov_dimension=2)
result = solve(problem, method=method, seed=7)
print(round(result.eigenvalue, 10))  # 1.0

Entry headings show the object's name. The anchor of an entry names a module path, usually the module that defines it, which can differ from the public import path. The import lines and the opening paragraphs of each page give the public import path of the objects you construct or call.

Find an entry by task

Task	Reference	Guide
Solve a problem and read the answer	Solve, plan and read results	Plan, compare and solve, Choose a problem and output
Build inputs from a matrix, Pauli sum, stencil or state	Inputs and input types	Supply inputs
Build a molecular Hamiltonian and its reference energies from a geometry	build_gcim_chemistry_problem	Chemistry inputs and reference energies
Plan, compare or estimate before running	Plan, compare and estimate	Plan, compare and solve
Count qubits, gates and shots of a Plan	Resource estimates	Estimate resources
Rank Plans by shots, width or predicted time	Rank candidate plans	Rank candidate plans
Check accuracy or verify a result	Accuracy and verification	Check accuracy and verify a result
Choose a backend, check device fit or export OpenQASM	Backends, profiles and export	Choose a backend, Check device fit and run time
Run step by step, continue an interrupted run, or reopen saved work	Run step by step, Save and reopen	Run on a backend, Continue an interrupted run, Save, load and reanalyze results
Configure a Method and read its Result	Algorithms	The guide in each row of that table
Build circuits from subroutines	Subroutines	Compose blocks
Pass your own circuit or write a Method	Extending NWQLib	Run your own circuit, Add a method

Algorithms

Computes	Methods	Reference and guide
Expectation of a Hermitian observable in a state	ExpectationMethod	Pauli expectation and the guide Finite Pauli expectation
Estimate of the smallest eigenvalue from Chebyshev moments	Lanczos	Lanczos and the guide Chebyshev Lanczos
Eigenphase or energy by phase estimation	QCELS, SPE, RFE, RWPE	QPE and the guide QPE
Estimate of the smallest eigenvalue in a fixed or adaptively grown trial basis	FixedGCIM, ADAPT	GCiM and ADAPT and the guide GCiM
Solution of du/dt = -A u + b	LCHS	LCHS and the guide LCHS
Solution of A x = b	QLS	QLS and the guide QLS
Candidate minimizer of an objective over a box	QHD	QHD and the guide QHD
Candidate minimizer subject to constraints, and box refinement	solve_augmented_lagrangian, refine_box	QHD constrained problems and box refinement and the guide Constrained problems

Subroutines

Builds	Reference
Block encodings of matrices	Block encoding
Linear combinations of unitaries (PREP and SELECT)	LCU
Coherent phase-estimation circuits	Coherent QPE
QSP and QSVT phases and circuits	QSP and QSVT
State preparation circuits, direct or from a matrix product state	State preparation
Evolution under a Pauli sum	Hamiltonian evolution
Fermionic operator pools and their generator circuits	Fermionic pools
Pauli decomposition of a matrix	Pauli decomposition
Trotter step counts with error bounds, and Trotter circuits	Trotterization