Noisy Quantum Gates

Implementation of the Noisy Quantum Gates model, published in Di Bartolomeo, 2023. It is a novel method to simulate the noisy behaviour of quantum devices by incorporating the noise directly in the gates, which become stochastic matrices.

Documentations

The documentation for Noisy Quantum Gates can be accessed on the website Read the Docs.

How to install

Requirements

The Python version should be 3.9 or later. Find your Python version by typing python or python3 in the CLI. We recommend using the repo together with an IBM Quantum Lab account, as it necessary for circuit compilation with Qiskit in many cases.

Installation as a user

The library is available on the Python Package Index (PyPI) with pip install quantum-gates.

Installation as a contributor

For users who want to have control over the source code, we recommend the following installation.

1. Clone the repository:

bash git clone https://github.com/CERN-IT-INNOVATION/quantum-gates.git

1. Navigate to the project directory:

bash cd quantum_gates

1. Create virtual environment

You can either use your IDE to set this up automatically or do it manually in the CLI. bash python -m venv venv source venv/bin/activate # On Windows use `venv\Scripts\activate` This saves your environment from pollution.

1. Install the package in editable mode.

bash pip install -e . This command installs the package in editable mode, allowing you to work directly with the source code. Any changes you make will be immediately available without the need to reinstall the package.

Quickstart

You can find this quickstart implemented in the tutorial notebook here.

Execute the following code in a script or notebook. Add your IBM token to by defining it as the variable IBMTOKEN = "yourtoken". Optimally, you save your token in a separate file that is not in your version control system, so you are not at risk of accidentally revealing your access token.

```python

Standard libraries

import numpy as np import json

Qiskit

from qiskit import QuantumCircuit, transpile from qiskit.visualization import plot_histogram

Own library

from quantumgates.simulators import MrAndersonSimulator from quantumgates.gates import standardgates from quantumgates.circuits import EfficientCircuit, BinaryCircuit from quantumgates.utilities import DeviceParameters from quantumgates.utilities import setupbackend IBMTOKEN = "" ``` We create a quantum circuit with Qiskit.

python circ = QuantumCircuit(2,2) circ.h(0) circ.cx(0,1) circ.barrier(range(2)) circ.measure(range(2),range(2)) circ.draw('mpl')

We load the configuration from a json file or from code with python config = { "backend": { "hub": "ibm-q", "group": "open", "project": "main", "device_name": "ibm_kyiv" }, "run": { "shots": 1000, "qubits_layout": [0, 1], "psi0": [1, 0, 0, 0] } } ... and setup the Qiskit backend used for the circuit transpilation.

python backend_config = config["backend"] backend = setup_backend(Token=IBM_TOKEN, **backend_config) run_config = config["run"]

This allows us to load the device parameters, which represent the noise of the quantum hardware. python qubits_layout = run_config["qubits_layout"] device_param = DeviceParameters(qubits_layout) device_param.load_from_backend(backend) device_param_lookup = device_param.__dict__()

Last, we perform the simulation ... ```python sim = MrAndersonSimulator(gates=standard_gates, CircuitClass=EfficientCircuit)

tcirc = transpile( circ, backend, schedulingmethod='asap', initiallayout=qubitslayout, seed_transpiler=42 )

probs = sim.run( tqiskitcirc=tcirc, qubitslayout=qubitslayout, psi0=np.array(runconfig["psi0"]), shots=runconfig["shots"], deviceparam=deviceparamlookup, nqubit=2, level_opt = 0)

``` ... and analyse the result.

python plot_histogram(probs, bar_labels=False, legend=['Noisy Gates simulation'])

If you want to use a non-linear topology you must use the BinaryCircuit and slightly modify the code. First of all we modify the qubit layout to match the topology of the device.

python config = { "run": { "shots": 1000, "qubits_layout": [0, 14], "psi0": [1, 0, 0, 0] } } Then also the command to import the parameter device has to change in order to import all the information of all the qubits up to the one with the max indices.

python device_param = DeviceParameters(list(np.arange(max(qubits_layout)+1))) device_param.load_from_backend(backend) device_param_lookup = device_param.__dict__()

Last, we perform the simulation ... ```python sim = MrAndersonSimulator(gates=standard_gates, CircuitClass=BinaryCircuit)

tcirc = transpile( circ, backend, schedulingmethod='asap', initiallayout=qubitslayout, seed_transpiler=42 )

probs = sim.run( tqiskitcirc=tcirc, qubitslayout=qubitslayout, psi0=np.array(runconfig["psi0"]), shots=runconfig["shots"], deviceparam=deviceparamlookup, nqubit=2, level_opt = 4)

``` ... and analyse the result.

python plot_histogram(probs, bar_labels=False, legend=['Noisy Gates simulation'])

Remember that the ouput of the simulator follows the Big-Endian order, if you want to switch to Little-Endian order, which is the standard for Qiskit, you can use the command

```python from quantumgates.utilities import fixcounts

nmeasuredqubit = 2 probslittleendian = fixcounts(probs, nmeasuredqubit) plothistogram(probslittleendian, bar_labels=False, legend=['Noisy Gates simulation']) ```

Usage

We recommend to read the overview of the documentation as a 2-minute preparation. You can import the package modules as shown in the Quickstart:

python from quantum_gates.simulators import MrAndersonSimulator from quantum_gates.gates import standard_gates from quantum_gates.circuits import EfficientCircuit from quantum_gates.utilities import DeviceParameters, setup_backend

Functionality

The main components are the gates, and the simulator. One can configure the gates with different pulse shapes, and the simulator with different circuit classes and backends. The circuit classes use a specific backend for the statevector simulation. The EfficientBackend has the same functionality as the StandardBackend, but is much more performant thanks to optimized tensor contraction algorithms. We also provide various quantum algorithms as circuits, and scripts to run the circuits with the simulator, the IBM simulator, and a real IBM backend. Last, all functionality is unit tested and one can get sample code from the unit tests.

Unit Tests

We recommend running the unit tests once you are finished with the setup of your environment. As some tests need access to IBM devices, you have to follow the steps outlined in token.py. Make sure that your token is active and you have accepted all license agreement with IBM in your IBM account. Before you run the tests, make sure that the device you are testing with (the on set in tests/simulation/testandersonsimulator.py) is available in your account and the device parameters are prepared in the tests/utility/device_parameters folder. In the future we might upgrade the tests and mock these dependencies.

Afer activating your virtual environment, you can run the tests from root with

bash python -m "pytest"

Using this command instead of just typing pytest will make sure that you are using the right Python version to run pytest. You can also just run a subset of the test, for example:

bash python -m pytest -k test_gates_noiseless_cnot_inv

How to contribute

Contributions are welcomed and should apply the usual git-flow: fork this repo, create a local branch named 'feature-...'. Commit often to ensure that each commit is easy to understand. Name your commits '[feature-...] Commit message.', such that it possible to differentiate the commits of different features in the main line. Request a merge to the mainline often. Contribute to the test suite and verify the functionality with the unit tests when using a different Python version or dependency versions. Please remember to follow the PEP 8 style guide, and add comments whenever it helps. You can run the linter with pylint .. The corresponding authors are happy to support you.

Build

You may also want to create your own distribution and test it. Navigate to the repository in your CLI of choice. Build the wheel with the command python3 -m build --sdist --wheel . and navigate to the distribution with cd dist. Use ls to display the name of the wheel, and run pip install <filename>.whl with the correct filename. Now you can use your version of the library.

Building the documentation

The documentation for Noisy Quantum Gates is built using Sphinx and is hosted on ReadTheDocs. If you wish to build and view the documentation locally, follow these steps:

1. Navigate to the docs directory:

From the root of the project, navigate to the docs folder:

bash cd docs

1. Install the documentation requirements:

bash pip install -r requirements.txt Note: It's recommended to perform this step in your virtual environment.

1. Build the HTML documentation:

Use the make command to build the HTML version of the documentation:

bash make html

1. View and check the documentation locally

Open the generated index.html file in your web browser to view the documentation:

bash open build/html/index.html # On macOS xdg-open build/html/index.html # On Linux start build\html\index.html # On Windows (Command Prompt)

Or manually navigate to the build/html directory and open index.html with your preferred web browser.

Credits

Please cite the work using the following BibTex entry:

text @article{PhysRevResearch.5.043210, title = {Noisy gates for simulating quantum computers}, author = {Di Bartolomeo, Giovanni and Vischi, Michele and Cesa, Francesco and Wixinger, Roman and Grossi, Michele and Donadi, Sandro and Bassi, Angelo}, journal = {Phys. Rev. Res.}, volume = {5}, issue = {4}, pages = {043210}, numpages = {19}, year = {2023}, month = {Dec}, publisher = {American Physical Society}, doi = {10.1103/PhysRevResearch.5.043210}, url = {https://link.aps.org/doi/10.1103/PhysRevResearch.5.043210} }

Authors

This project has been developed thanks to the effort of the following people:

• Giovanni Di Bartolomeo (dibartolomeo.giov@gmail.com)
• Michele Vischi (vischimichele@gmail.com)
• Francesco Cesa
• Michele Grossi (michele.grossi@cern.ch)
• Sandro Donadi
• Angelo Bassi
• Paolo Da Rold
• Roman Wixinger (roman.wixinger@gmail.com)