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Ankaa and Cepheus QPUsRigetti Computing—
Ankaa and Cepheus QPUs
Courtesy of Rigetti Computing (photo: Drew Bird Photography) · Press kit, editorial use (opens rigetti.com)

Ankaa and Cepheus QPUs

by Rigetti ComputingUS

PilotStage 3 of 5

Scaling multi-chip systems toward 100+ qubits at 99.5% two-qubit fidelity.

Updated 21 May 2026Checked 25 Sep0 updates this week

Milestones

Next · 100+ qubit chiplet system
  1. Ankaa-2 (84 qubits)Dec 2023Complete.
  2. Ankaa-3 with 99.5% median two-qubit fidelityDec 2024Complete.
  3. Cepheus-1-36Q multi-chip systemAug 2025Complete.
  4. 100+ qubit chiplet systemNowCurrent milestone.

Most important updates

  • 21 May 2026
  • Aug 2025
  • Feb 2025
  • Dec 2024

Current obstacles

  • Chip-to-chip coupling qualityGates across chiplet edges must be as good as gates within one chip, so the tiles act as one device.

Physics limits

  • Defects in materials limit qubit lifeQubit lifetimes are limited by microscopic defects in oxides and surfaces of the chip, which absorb energy from the qubit. Better materials help, but no process is defect-free.
  • Qubit frequencies collideEach qubit sits at a microwave frequency of a few gigahertz. Small fabrication spreads mean neighbours can land too close in frequency, causing crosstalk that gets harder to avoid as counts grow.
  • Links between chiplets are imperfectCoupling qubits across two chiplets passes through bumps and gaps that add loss and variation, so cross-chip gates tend to be worse than gates within one chip.

How it works

3 parts
Inside the Ankaa-3 system's cryostat: control lines run down gold stages, each colder than the last, to the superconducting chip at the bottom
Inside the Ankaa-3 system's cryostat: control lines run down gold stages, each colder than the last, to the superconducting chip at the bottomCourtesy of Rigetti Computing (photo: Drew Bird Photography) · Press kit, editorial use (opens investors.rigetti.com)
Qubit

Superconducting circuits

Each qubit is a tiny aluminium circuit with a Josephson junction, cooled to about 10 mK and driven by microwave pulses.

Chiplets

Tiling small chips

Instead of one large chip, 9-qubit chiplets are joined in one package. Small chips yield better and can be tested before assembly.

Gates

Tunable couplers

Couplers between qubits switch interactions on for two-qubit gates; Ankaa-3 reached a 99.5% median two-qubit fidelity.

Update log

4 updates

Thu 21 May

  • Minor: PressFunding

Aug 2025

  • Minor: PressHardware

Feb 2025

  • Minor: PressPartnership

Dec 2024

  • Minor: PressHardware

About Rigetti Computing

The team behind Ankaa and Cepheus QPUs

Rigetti Computing

Superconducting chips, chiplets, Novera

Rigetti makes superconducting quantum chips in its own fab in Fremont, California. It sells them via the cloud and as on-site Novera units, and scales by tiling small chiplets.

  • Cepheus-1-36Q (2025) joined four 9-qubit chiplets at 99.5% median two-qubit fidelity.
  • Quanta Computer invested $35M and agreed to spend $250M on joint development (2025).
  • Owns its chip factory, Fab-1.

rigetti.com (opens rigetti.com)Company profile →

Founded
201313 yrs
Headquarters
United States
Status
Public
Listed
RGTI (opens google.com)NASDAQ
Valuation
public
Works in
QuantumSuperconducting
Coverage
1 program · 5 updateslatest 21 May 2026checked 25 Sep
People
Subodh KulkarniCEO
Primer