# #

Mitiq is a Python toolkit for implementing error mitigation techniques on quantum computers.

Current quantum computers are noisy due to interactions with the environment, imperfect gate applications, state preparation and measurement errors, etc. Error mitigation seeks to reduce these effects at the software level by compiling quantum programs in clever ways.

Want to know more? Check out our documentation and chat with us on Discord.

Do you use near-term quantum hardware? Have you tried Mitiq? Either way, take our survey and help make Mitiq better! bit.ly/mitiq-survey

## Quickstart#

### Installation#

```
pip install mitiq
```

### Example#

Define a function which inputs a circuit and returns an expectation value you want to compute, then use Mitiq to mitigate errors.

```
import cirq
from mitiq import zne, benchmarks
def execute(circuit: cirq.Circuit, noise_level: float = 0.001) -> float:
"""Returns Tr[ρ |0⟩⟨0|] where ρ is the state prepared by the circuit with depolarizing noise."""
noisy_circuit = circuit.with_noise(cirq.depolarize(p=noise_level))
return cirq.DensityMatrixSimulator().simulate(noisy_circuit).final_density_matrix[0, 0].real
circuit: cirq.Circuit = benchmarks.generate_rb_circuits(n_qubits=1, num_cliffords=50)[0]
true_value = execute(circuit, noise_level=0.0) # Ideal quantum computer.
noisy_value = execute(circuit) # Noisy quantum computer.
zne_value = zne.execute_with_zne(circuit, execute) # Noisy quantum computer + Mitiq.
print(f"Error (w/o Mitiq): %0.4f" %abs((true_value - noisy_value) / true_value))
print(f"Error (with Mitiq): %0.4f" %abs((true_value - zne_value) / true_value))
```

Sample output:

```
Error (w/o Mitiq): 0.0688
Error (with Mitiq): 0.0002
```

See our guides and examples for more explanation, techniques, and benchmarks. The examples and other notebooks can be run interactively on the cloud with mybinder.org.

## Quick Tour#

### Error mitigation techniques#

Technique |
Documentation |
Mitiq module |
Paper Reference(s) |
---|---|---|---|

Zero-noise extrapolation |
|||

Probabilistic error cancellation |
|||

(Variable-noise) Clifford data regression |
|||

Dynamical decoupling |
(In progress) |
(In progress) |

See our roadmap for additional candidate techniques to implement. If there is a technique you are looking for, please file a feature request.

### Interface#

We refer to any programming language you can write quantum circuits in as a *frontend*, and any quantum computer / simulator you can simulate circuits in as a *backend*.

#### Supported frontends#

Note: Cirq is a core requirement of Mitiq and is installed when you `pip install mitiq`

.

#### Supported backends#

You can use Mitiq with any backend you have access to that can interface with supported frontends.

### Citing Mitiq#

If you use Mitiq in your research, please reference the Mitiq preprint (bibtex). A list of papers citing Mitiq can be found on Google Scholar / Semantic Scholar.

## License#

## Contributing#

We welcome contributions to Mitiq including bug fixes, feature requests, etc. To get started, check out our contribution guidelines and/or documentation guidelines. An up-to-date list of contributors can be found here and below.

## Contributors ✨#

Thanks goes to these wonderful people (emoji key):

This project follows the all-contributors specification. Contributions of any kind welcome!