IBM Quantum Heron r3 (ibm_pittsburgh)
IBM Quantum Heron r3 (ibm_pittsburgh)
Register profile — the machine's variant of its architecture
qubit type: fixed-frequency transmon + flux-tunable coupler
gate mechanism: native CZ
connectivity: heavy-hex, mean degree 2.3; 57 of 176 couplings below 1e-3
control: room-temperature RF, high-density flex
control placement: room-temp
readout: multiplexed dispersive
gate evidence: a published figure (source class not yet tagged)
codes: dynamic_compass, heavy_hex, quantum_repetition, rotated_surface, spacetime_circuit, stab_4_2_2, steane, triangular_color
flags: conflicting claims
Technologies by layer — the machine's cell per layer
| 1 Qubit carrier | |
| 2 Encoding | Bare physical qubit (no encoding) · primary ◌ 🔎 Bare two-level subspace — Computational subspace of an anharmonic oscillator; leakage to |2⟩ is the price. |
| 3 Gate mechanism | Tunable-coupler CZ / iSWAP · primary ▨ ✅ native CZ via flux-tunable coupler, ZZ-free idling; median CZ error 1.52×10⁻³ (Jul 2025) |
| 4 Connectivity / transport | Static nearest-neighbour lattice · primary ▦ ✅ heavy-hex, degree ≤3, mean 2.3; 57 of 176 couplings below 1×10⁻³ 2Q error (QDC 2025) |
| 5 Control | Room-temperature electronics + per-qubit coax/flex · primary ▨ 🔎 room-temperature RF with high-density flex cabling |
| 6 Readout | Dispersive microwave readout (+TWPA, Purcell) · primary ▨ ✅ multiplexed dispersive; median readout error 1.3×10⁻² (Jul 2025); mid-circuit measurement + feed-forward in production |
| 7 Code | Rotated surface code (+ yoked variants) · primary ▤ abstract; ibm_pittsburgh runs ✅ rotated surface (3,3),(3,5),(5,3) memory up to 10 cycles on ibm_pittsburgh; heavy-hex d=5 memory to 30 rounds (arXiv:2604.14296) (sweep 7 Oct 2026, source read) Colour code (transversal Cliffords) · alternate ▤ abstract; colour-code results ✅ two d=5 triangular 6.6.6 colour-code logical qubits (38 physical), logical Bell state better than physical to depth 20 (sweep 7 Oct 2026, source read) Error-detection codes ([[4,2,2]], d=2 surface, iceberg, spacetime) · alternate ▤ Abstract (v3) 🔎 spacetime-code error detection with syndrome post-selection: 64-qubit, depth-73 Clifford circuit doped with 314 T gates on 76 physical qubits; ~10× error suppression; fidelity lower bound 0.349 at 95% confidence (v3, 2 Sep 2026) Magic-state factory (cultivation / distillation / code switching) · alternate ▤ 🔎 rotated_surface magic-state injection (ibm_fez): |H_L⟩ 0.8806(2), |T_L⟩ 0.8665(3) at 36.28% acceptance Error mitigation in the code slot (ZNE, PEC) — not a code · alternate ▤ Abstract; §Experiments ('ibm_boston Heron r3 processor'); also arXiv:2607.25998 ✅ QESEM (PEC-type unbiased and ZNE-type extrapolated) on the ibm_boston Heron r3 processor, 51- and 74-qubit heavy-hex circuits (Jul 2026); Algorithmiq et al. PEC on a 56-qubit section of ibm_boston |
| 8 Decoder | — none — nothing in this layer ▣ Fig. 1c (fault classification, rejected faults); SI §S2 ✅ no decoder in loop; detection with post-selection, no closed-loop correction |
| 9 Interconnect | — none — nothing in this layer ◌ 🔎 monolithic single 156-q die; no interconnect in production (m-coupler prototyped on Crossbill, l-coupler on Flamingo) |
| 10 Manufacturing | Superconducting-qubit lithography (Al/AlOx/Al junctions, Nb wiring, 300 mm) · primary ◌ 🔎 IBM 300 mm Albany superconducting-qubit lithography; flip-chip + TSV + multi-level wiring |
Standard records
acceptance fraction → 5.90e-4 · best (spacetime detection code)
2,051 accepted samples in 16.1 min of QPU time · Jul 2026 · source
2Q error under full-width parallel operation → 1.52e-3 · best (median CZ)
Jul 2025 · source
SPAM error → 0.013 · typical (median readout error)
Jul 2025 · source
T2 coherence (echo/DD) → 350 µs · typical
2025 · source
evidence: ✅ 8 / 14