IBM Quantum Heron r3 (ibm_pittsburgh)

fixed-frequency transmon + flux-tunable coupler; 156 q, 176 couplers, T2 ~350 µs (ibm_pittsburgh, DEPLOYED Jul 2025)

Bare two-level subspace — Computational subspace of an anharmonic oscillator; leakage to |2⟩ is the price.

native CZ via flux-tunable coupler, ZZ-free idling; median CZ error 1.52×10⁻³ (Jul 2025)

heavy-hex, degree ≤3, mean 2.3; 57 of 176 couplings below 1×10⁻³ 2Q error (QDC 2025)

room-temperature RF with high-density flex cabling

multiplexed dispersive; median readout error 1.3×10⁻² (Jul 2025); mid-circuit measurement + feed-forward in production

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)

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)

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)

rotated_surface magic-state injection (ibm_fez): |H_L⟩ 0.8806(2), |T_L⟩ 0.8665(3) at 36.28% acceptance

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

no decoder in loop; detection with post-selection, no closed-loop correction

monolithic single 156-q die; no interconnect in production (m-coupler prototyped on Crossbill, l-coupler on Flamingo)

IBM 300 mm Albany superconducting-qubit lithography; flip-chip + TSV + multi-level wiring