add hea_symm.py example

Author: liwt31

.github/workflows/ci.yml

@@ -27,6 +27,10 @@ jobs:
  pytest tencirchem tests --durations=0 --cov=tencirchem
  - name: Upload coverage to Codecov
  uses: codecov/codecov-action@v3
+ - name: run examples
+ run: |
+ cd example; bash run.sh
+ cd ..
  - name: test build doc
  run: |
  sudo apt install pandoc

README.md

@@ -15,7 +15,7 @@ TenCirChem is based on [TensorCircuit](https://github.com/tencent-quantum-lab/te
 and is optimized for chemistry applications.
 
 ## Easy Installation
-Getting started with TenCirChem is a breeze. Simply install the package via pip:
+Getting started with TenCirChem by installing the package via pip:
 
 ```sh
 pip install tencirchem

example/README.md

@@ -0,0 +1,17 @@
+# Examples
+
+- `custom_excitation.py`: Specify custom excitation operators for unitary coupled-cluster (UCC) ansatz.
+- `hea_beh2.py`: VQE of BeH2 based on hardware-efficient ansatz (Ry ansatz), with (4e, 4o) active space.
+- `hea_lih.py`: VQE of LiH based on hardware-efficient ansatz (Ry ansatz), with (2e, 3o) active space.
+- `hea_symm.py`: VQE of H4 based on symmetry-preserving hardware-efficient ansatz.
+- `mr_uccsd.py`: Multi-reference UCCSD calculation of the bond dissociation limit of the water molecule.
+- `noisy_circuit.py`: Exemplary noisy circuit simulation based on hardware-efficient ansatz.
+- `print_circuit.py`: Draw UCCSD circuit for H2.
+- `pyrazine_spectra.py`: Absorption spectrum of the pyrazine molecule by variational quantum dynamics (VQD).
+- `pyscf_compatibility.py`: TenCirChem CI vector/reduced density matrices follow the convention of PySCF.
+- `sbm_dynamics.py`: Spin relaxation of the spin-boson model by variational quantum dynamics.
+- `simple_kupccgsd.py`: Simple k-UpCCGSD calculation with multiple initial guess.
+- `simple_uccsd.py`: Simple UCCSD calculation.
+- `switch_backend.py`: Switch backend at runtime.
+- `ucc_classes.py`: UCC subclasses share the same interface.
+- `water_pes.py`: Water potential energy curve with 6-31G(d) basis set, enabled by GPU acceleration.

example/hea_symm.py

@@ -0,0 +1,50 @@
+import numpy as np
+from tensorcircuit import Circuit
+
+from tencirchem import UCC, HEA, set_backend
+from tencirchem.molecule import h4
+
+K = set_backend("jax")
+
+ucc = UCC(h4)
+# reference energies
+ucc.print_energy()
+
+
+# symmetry preserving ansatz: npjqi 6:10, 2020
+n_layers = 5
+n_params = n_layers * (ucc.n_qubits - 2)
+def circuit(params):
+ params = params.reshape(n_layers, ucc.n_qubits - 2)
+ c = Circuit(ucc.n_qubits)
+ # HF initial state
+ for i in range(ucc.n_elec // 2):
+ c.x(ucc.n_qubits - 1 - i)
+ c.x(ucc.n_qubits // 2 - 1 - i)
+ for l in range(n_layers):
+ indices = list(range(0, ucc.n_qubits - 1, 2)) + list(range(1, ucc.n_qubits - 1, 2))
+ for i in indices:
+ if i < ucc.n_qubits // 2 - 1:
+ theta = params[l, i]
+ elif i == ucc.n_qubits // 2 - 1:
+ # preserve s_z
+ theta = 0
+ else:
+ theta = params[l, i-1]
+ unitary = K.convert_to_tensor([[1, 0, 0, 0],
+ [0, K.cos(theta), K.sin(theta), 0],
+ [0, K.sin(theta), -K.cos(theta), 0],
+ [0, 0, 0, 1]])
+ c.any(i, (i + 1), unitary=unitary)
+ return c
+
+
+es = []
+for i in range(10):
+ init_guess = (np.random.rand(n_params) - 0.5)
+ hea = HEA(ucc.h_qubit_op, circuit, init_guess, engine="tensornetwork")
+ # default parameter shift doesn't work for this type of circuit
+ hea.grad = "autodiff"
+ e = hea.kernel()
+ es.append(e)
+print(sorted(es))

example/run.sh

@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2023. The TenCirChem Developers. All Rights Reserved.
+#
+# This file is distributed under ACADEMIC PUBLIC LICENSE
+# and WITHOUT ANY WARRANTY. See the LICENSE file for details.
+#
+
+export PYTHONPATH=../:PYTHONPATH
+code=0
+for python_args in *.py; do
+ echo ============================$python_args=============================
+ timeout 20s python $python_args
+ exit_code=$?
+ echo ============================$python_args=============================
+ # if not the time out exit code or normal exit code
+ if [ $exit_code -ne 124 ] && [ $exit_code -ne 0 ]; then
+ echo "The script failed with exit code $exit_code" >&2
+ code=1
+ fi
+done
+
+exit $code