IQM Garnet

Overview

IQM Garnet is the 20-qubit processor at the heart of IQM's current product range for research and education. Its qubits sit on a square lattice, which matches the layout used for surface-code error correction, and each pair of neighbors is linked by a tunable coupler that can turn their interaction on and off. IQM describes it as the representative of its qubit crystal family, the same technology used in its larger on-premises Radiance systems.

Garnet is available in several ways. Users can run programs on it through Amazon Braket or IQM's own Resonance cloud, and customers such as national laboratories and universities have bought systems built around it.

History and background

IQM was founded in 2018 as a spin-off from Aalto University and VTT in Finland. It built several generations of smaller processors before announcing Garnet. In February 2024 the company published benchmarks for the 20-qubit computer, including the median CZ gate fidelity of 99.51% and a 20-qubit GHZ state, and in May 2024 Garnet became available on Amazon Braket, which was the first time IQM computers were offered through a self-service cloud.

Garnet's architecture was designed to scale. IQM followed it with Emerald, a 54-qubit processor on the same architecture with 99.5% median CZ fidelity, and plans to scale the square-lattice design to 150 qubits. In 2024 IQM also reported a 99.9% two-qubit gate fidelity on a planar transmon in a research device, and it has developed a Star topology that uses a central resonator to link qubits.

How it works

Garnet's qubits are flux-tunable transmons, superconducting circuits whose frequency can be adjusted with a magnetic flux. They sit on a square lattice rotated by 45 degrees, forming an effective 5 by 5 grid with 20 qubits in the occupied sites. Between each pair of neighboring qubits is a tunable coupler, itself a flux-tunable transmon. When the coupler is set to one frequency, the qubits are decoupled, and when it is moved, the qubits interact.

The native gates are a phased X rotation (PRX) for single qubits and a controlled-Z (CZ) for pairs. A CZ takes about 20 to 40 nanoseconds and is carried out by moving qubit frequencies toward an avoided crossing for a short time. The tunable-coupler design allows fast gates while keeping idle crosstalk low, and IQM reports a CZ with fidelity of 99.81% in a research version of the architecture.

A system built around Garnet includes IQM's in-house control electronics, a dilution refrigerator, and software for calibration and job management. IQM publishes benchmark data, including randomized benchmarking, quantum volume, and GHZ fidelity, so users can compare the system with others on a consistent basis.

Connectivity

Square lattice: each qubit connects to up to four neighbors through tunable couplers (30 qubit pairs)

Specifications in detail

Key features

• 20 qubits in a square lattice with tunable couplers
• Median two-qubit CZ fidelity of 99.51% across 30 pairs; best pair 99.8%
• Median single-qubit fidelity about 99.9%
• 20-qubit GHZ state fidelity above 0.5, confirming genuine multi-qubit entanglement (about 0.62 with readout error mitigation)
• Available on Amazon Braket since May 2024

Limitations

• 20 qubits is small compared with IBM or Google chips
• Coherence times of around 40 microseconds limit circuit depth
• Raw GHZ fidelity falls below 0.5 for more than 12 qubits without readout error mitigation
• Tunable-coupler control adds calibration complexity

Timeline

What it is used for

• Teaching and training in quantum programming
• Testing algorithms with surface-code-compatible connectivity
• Hybrid HPC research when combined with supercomputers
• Benchmarking and calibration research

How it compares

• Compared with IBM Heron (156 qubits), Garnet has far fewer qubits and a similar two-qubit fidelity range, with an open, published benchmark set.
• Compared with the RIKEN-Fujitsu 64-qubit computer, it is a smaller European counterpart built with in-house electronics.
• Compared with Rigetti Novera (9 qubits), it is more than twice as large, with a comparable approach to tunable couplers.

Technical notes

A GHZ state is a maximally entangled state of all qubits. If its measured fidelity is above 0.5, the system must contain genuine multi-qubit entanglement across all qubits. IQM reported a fidelity above 0.5 for 20 qubits after readout error mitigation, with a value of about 0.62. It is a useful, if demanding, system-level test, because every error in every gate and measurement lowers the score.

Why it matters

Garnet is a good example of a mid-sized processor that is useful for learning and for early research, and its published benchmarks show how fidelity and entanglement tests are done in practice. It also anchors IQM's strategy of selling on-premises systems that connect with supercomputers.

For readers comparing machines, Garnet is a reminder that fidelity numbers should come with context: median versus best-pair values, the pairs and dates measured, and whether readout error mitigation was applied.

Frequently asked questions

Keep exploring

• Company profile: IQM
• Related processor: IBM Heron (r1, r2, and r3)
• Related processor: Rigetti Novera QPU
• Related processor: RIKEN-Fujitsu 64-Qubit Superconducting Quantum Computer
• Related processor: Origin Wukong

This profile is written for educational purposes and summarizes company announcements, published papers, and vendor specification sheets. Last reviewed: September 30, 2026. Figures marked as company-reported have not all been independently verified, and benchmarks differ between vendors, so compare them with care.

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