# #

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.

## 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, noise_level=0.005):
"""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 = 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: {abs((true_value - noisy_value) / true_value):.3f}")
print(f"Error w Mitiq: {abs((true_value - zne_value) / true_value):.3f}")
```

Sample output:

```
Error w/o Mitiq: 0.264
Error w Mitiq: 0.073
```

### Calibration#

Unsure which error mitigation technique or parameters to use? Try out the calibration module demonstrated below to help find the best parameters for you particular backend!

See our guides and examples for more explanation, techniques, and benchmarks.

## Quick Tour#

### Error mitigation techniques#

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

Zero-noise extrapolation |
|||

Probabilistic error cancellation |
|||

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

Digital dynamical decoupling |
|||

Readout-error mitigation |

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 whitepaper using the bibtex entry found in `CITATION.bib`

.

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.

## Contributors ✨#

Thank you to all of the wonderful people that have made this project possible. Non-code contributors are also much appreciated, and are listed here. Thank you to

@francespoblete for much of Mitiq’s design work/vision

Contributions of any kind are welcome!