What is The QEM Zoo?

The QEM Zoo is a comprehensive, freely accessible catalog of quantum error mitigation (QEM) and quantum error suppression (QES) techniques. It aims to be a living reference for researchers, students, and practitioners working with near-term quantum computers.

The site is inspired by similar community resources like the Complexity Zoo and the Error Correction Zoo.

Why does quantum error mitigation matter?

Today's quantum computers are noisy. Gate errors, decoherence, and crosstalk corrupt computations well before they finish, and full fault-tolerant quantum error correction — which can suppress these errors to arbitrarily low levels — requires hardware resources far beyond what current devices offer. This leaves a gap: we have quantum processors that are too noisy to run deep circuits reliably, yet too small to encode logical qubits with error-correcting codes.

Quantum error mitigation (QEM) and quantum error suppression (QES) techniques bridge this gap. Rather than correcting errors at the hardware level, they use clever circuit design, classical post-processing, and statistical methods to extract more accurate answers from noisy results. These techniques are what make it possible to do useful work on near-term quantum hardware — and understanding their strengths, limitations, and tradeoffs is essential for anyone working with today's quantum devices.

Why does this exist?

The need for such a resource was identified as an open problem in the comprehensive review "Quantum Error Mitigation" by Cai et al. (2023), published in Reviews of Modern Physics. The field of quantum error mitigation has grown rapidly, with dozens of techniques proposed across hundreds of papers. Keeping track of all these methods, their relationships, tradeoffs, and applications has become increasingly difficult.

The QEM Zoo aims to fill this gap by providing a structured, searchable, and continuously updated reference that organizes this knowledge in one place.

How do I navigate the site?

The site is organized into several main sections:

• Protocols - The main catalog of QEM and QES methods (e.g., ZNE, PEC, dynamical decoupling)
• Techniques - Supporting methods like noise scaling and extrapolation
• Noise - Types of quantum noise and which techniques address them
• Applications - Real-world use cases like VQE, QAOA, and quantum simulation
• Visualize - Interactive charts showing tradeoffs and technique relationships

Each page has a search bar and category filters. You can also use the A-Z navigation to jump to techniques alphabetically. Click on any technique name to see its detailed page with equations, references, and related methods.

What do the bias/variance/overhead ratings mean?

On the Visualize page and in technique details, you'll see metrics for:

• Bias - How much systematic error remains after mitigation (lower is better)
• Variance - How much statistical noise is introduced (lower is better)
• Overhead - Additional computational cost (circuit executions, classical processing)

These are qualitative assessments meant to help compare techniques. Real-world performance depends heavily on the specific noise model, circuit, and implementation.

Where can I learn more about quantum error mitigation?

Here are some recommended resources:

• Review Paper: Quantum Error Mitigation (Cai et al., 2023) - Comprehensive review in Reviews of Modern Physics
• Software: Mitiq - Open-source Python library for quantum error mitigation by Unitary Fund
• Related Resource: Error Correction Zoo - Catalog of quantum error correcting codes

How do I cite this resource?

If you find The QEM Zoo useful in your research, please cite it as:

Or in plain text:

I found an error or have a suggestion. How do I report it?

I welcome corrections, suggestions, and contributions! If you've found an error, have a technique to add, or want to suggest improvements, please reach out:

Click to reveal email

When reporting errors, please include:

• The specific page or technique where the error appears
• What the error is and what the correct information should be
• A reference (paper, textbook, etc.) supporting the correction, if applicable

Can I contribute a new technique or application?

Yes! If you know of a QEM/QES technique that isn't covered, or if you have detailed information to add to an existing entry, please reach out. Contributions with references to peer-reviewed papers are especially appreciated.