This is a rapidly evolving project - documentation and materials from previous recordings may become outdated quickly. If you encounter any inconsistencies or have questions, please open an issue.

TQEC

TQEC (Topological Quantum Error Correction) is a design automation software for representing, constructing and compiling large-scale fault-tolerant quantum computations based on surface code and lattice surgery.

In the past decade, there have been significant advancements in surface code quantum computation based on lattice surgery. However, the circuits required to implement these protocols are highly complex. To combine these protocols for constructing larger-scale computation, a substantial amount of effort is needed to manually encode the circuits, and it is extremely challenging to ensure their correctness. As a result, many complex logical computations have not been practically simulated.

tqec provides numerous building blocks based on state-of-the-art protocols, with verified correct circuits implementation for each block. These blocks can then be combined to construct large-scale logical computations, enabling the automatic compilation of large-scale computational circuits.

NOTE: This project is under active development and provide no backwards compatibility at current stage.

Documentation is available at https://tqec.github.io/tqec/index.html

Installation

Currently, you need to install tqec from source with pip or uv:

With pip:

python -m pip install git+https://github.com/tqec/tqec.git

With uv:

uv pip install git+https://github.com/tqec/tqec.git

For a more detailed installation guide and common troubleshooting tips, see the installation page in the documentation.

Basic Usage

Here we generate the circuits for a logical CNOT between two logical qubits to demonstrate how to use the tool. Refer to quick start in the documentation for more detailed explanation.

from pathlib import Path

from tqec import BlockGraph, compile_block_graph, NoiseModel

# 0. Path to the logical_cnot.dae file
cnot_dae_filepath = Path.cwd() / "assets" / "logical_cnot.dae"
if not cnot_dae_filepath.exists():
    print(f"The file '{cnot_dae_filepath}' does not exist.")

# 1. Construct the logical computation
block_graph = BlockGraph.from_dae_file(cnot_dae_filepath)

# 2. Get the correlation surfaces of interest and compile the computation
correlation_surfaces = block_graph.find_correlation_surfaces()
compiled_computation = compile_block_graph(block_graph, observables=[correlation_surfaces[1]])

# 3. Generate the `stim.Circuit` of target code distance
circuit = compiled_computation.generate_stim_circuit(
    # k = (d-1)/2 is the scale factor
    # Large values will take a lot of time.
    k=2,
    # The noise applied and noise levels can be changed.
    noise_model=NoiseModel.uniform_depolarizing(0.001),
)

See the user guide for more tutorials.

Contributing

Pull requests and issues are more than welcomed!

See the contributing page for for specific instructions to start contributing.

Community

Every Wednesday at 8:30am PST, we hold meetings to discuss project progress and conduct educational talks related to TQEC.

Here are some helpful links to learn more about the community:

• Overview of state of the art 2D QEC: Slides/Video
• Community questions and answers: Docs
• Introduction to surface code quantum computation: Slides
• Programming a quantum computer using SketchUp: Slides/Video

All the resources and group meeting recordings are available at this link.

Please join the Google group to receive more updates and information!

Ethical notice

This library is intended for academic, educational, and civilian research only, in the field of fault-tolerant quantum computing, particularly in surface code compilation and topological error correction.

It is made freely and publicly available without access restrictions, in the interest of advancing open scientific and academic collaboration.

The maintainers request that users and contributors refrain from engaging in, supporting, or facilitating military, surveillance, or dual-use applications.

Please, review the full ETHICAL_NOTICE.md for important terms regarding export control, ethical use, and contributor responsibilities.