Qiskit Cold Atom

Qiskit is an open-source SDK for working with quantum computers at the level of circuits, algorithms, and application modules.

This project builds on this functionality to describe programmable quantum simulators of trapped cold atoms in a gate- and circuit-based framework. This includes a provider that allows access to cold atomic quantum devices located at Heidelberg University.

Traditionally, each wire in a quantum circuit represents one qubit as the fundamental unit of information processing. Here, we extend this concept and allow wires to represent individual internal states of trapped cold atoms. This currently covers two settings, one for fermionic modes and one for spin modes, demonstrating that a broad range of hardware can be accommodated in Qiskit.

We encourage new users to familiarize themselves with the basic functionalities through the tutorial-style python notebooks in docs/tutorials. These require an environment to execute .ipynb notebooks such as jupyter lab.

Installation

To install Qiskit Cold Atom from source and further develop the package, clone this repository and install from the project root using pip:

pip install -e .

To use the repository you can also install using either

pip install git+https://github.com/qiskit-community/qiskit-cold-atom.git

or Pypi

pip install qiskit-cold-atom

To install Qiskit Cold Atom with the ffsim fermion simulator backend (not supported on Windows), specify the ffsim extra in the pip install command, e.g.

pip install "qiskit-cold-atom[ffsim]"

Setting up the Cold Atom Provider

Qiskit Cold Atom includes local simulator backends to explore the cold atomic hardware. In order to access remote device backends, you will need valid user credentials. To this end, the user has to specify the url of the desired backend and a valid username and token as a password, which can be saved as an account:

from qiskit_cold_atom.providers import ColdAtomProvider

# save an account to disk
ColdAtomProvider.save_account(urls = ["url_backend_1", "url_backend_2"], username="my_name", token="my_password") 

Loading the account instantiates the provider from which the included backends can be accessed.

# load the stored account
provider = ColdAtomProvider.load_account()

# get available backends
print(provider.backends())

# Example: Get a simulator backend
spin_simulator_backend = provider.get_backend("collective_spin_simulator")

Cold atomic circuits

The circuits that can be run on the cold atomic hardware explored in this project use different gates from the circuits typically employed in Qiskit, because these hardware are not built from qubits, but from fermions or spins. Qiskit Cold Atom includes basic simulators for both the fermion and spin settings that can be used to simulate small circuits. See Introduction & Fermionic Circuits and Spin circuits for tutorials on how to define and run gates through quantum circuits in these settings.

Qiskit Cold Atom also includes a high-performance simulator for fermionic circuits based on ffsim, which can handle much larger circuits than the basic simulator mentioned before. The ffsim simulator is not supported on Windows, and in order for it to be available, Qiskit Cold Atom must be installed with the ffsim extra, e.g.

pip install "qiskit-cold-atom[ffsim]"

Documentation

The documentation can be found as Github pages here https://qiskit-community.github.io/qiskit-cold-atom/. To build the API reference locally, run:

pip install -r requirements-dev.txt
make -C docs html
open docs/_build/html/index.html

Tests

Test are located in the test folder. All contributions should come with test files that are named test_*.py which test the new functionalities. To execute the test suite locally, run

python -m unittest

from the project root.

License

Apache License 2.0.