Zuchongzhi 3.2

Raveh Neeman

doi:10.5281/zenodo.22674814

USTC / Hefei National Laboratory · superconducting circuits · DEMONSTRATED (22 Dec 2025) · 107 physical qubits · access: research cloud by application with expert review (QuantumCTek cloud: 107 readable qubits + 187 couplers)

architecture: Transmon lattice with tunable couplers · Open on the map

Register profile — the machine's variant of its architecture

qubit type: tunable transmon + tunable coupler

gate mechanism: tunable coupler CZ

connectivity: lattice; coupler geometry not published

control: room-temperature RF; all-microwave leakage-reduction units on data qubits + fast unconditional ancilla reset inside the QEC cycle

control placement: room-temp

readout: dispersive, 0.95% readout error in a 300 ns window

gate evidence: a published figure (source class not yet tagged)

decoder mode: offline — syndromes decoded after the run

codes: xzzx

Technologies by layer — the machine's cell per layer

1 Qubit carrier	Transmon · primary ▣ Fig. 1b (patches mapped onto superconducting-qubit lattice) 🔎 tunable transmons + tunable couplers (Zuchongzhi-3 platform); 107 on chip, 97 used for QEC
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 ▤ 🔎 tunable-coupler CZ (Zuchongzhi-3 platform); 2Q error roughly 2× Google Willow's
4 Connectivity / transport	Static nearest-neighbour lattice · primary ▣ Fig. 1b (d=3 patches mapped onto qubit lattice) ✅ lattice; coupler geometry not published; d=7 rotated surface code across the 97-qubit patch
5 Control	Room-temperature electronics + per-qubit coax/flex · primary ▤ ✅ room-temperature RF; all-microwave leakage suppression inside one QEC cycle, avoiding the extra DC lines of DC-pulse leakage removal (Dec 2025)
6 Readout	Dispersive microwave readout (+TWPA, Purcell) · alternate ▤ ✅ dispersive; 0.95% readout error in a 300 ns window (Dec 2025) Fast unconditional / dissipative qubit reset · alternate ▤ ✅ fast unconditional ancilla reset inside each QEC cycle, paired with microwave LRUs (Dec 2025) — (Atlas gap: ∅G-lru) · primary ▤ ✅ all-microwave leakage-reduction units on data qubits; leakage population suppressed 72× to 6.4(5)×10⁻⁴ after 40 cycles (Dec 2025)
7 Code	Rotated surface code (+ yoked variants) · primary ▣ Fig. 1a–b (patch-based surface-code layout); Fig. 3 (logical CNOT) ✅ rotated_surface/surface-17: d=3, d=5 on subsets, d=7 on 97 q over 40 cycles, Λ = 1.40(6) (Dec 2025); logical CNOT/H/S on d=3 patches (Jul 2026)
8 Decoder	Neural decoders (AlphaQubit 2, CNN, transformers) · primary ▣ Fig. 2d, 3c (decoded fidelities); main text: neural-network decoder ✅ neural-network decoding for logical CNOT + H + S on d=3 patches, multi-round syndromes, no post-selection; CNOT process fidelity 0.643(2) (Jul 2026) — none — nothing in this layer ▤ 🔎 no decoder named for the d=7 memory; no real-time decoding claimed; treated as offline
9 Interconnect	Multi-die packaging in one module (flip-chip, bump-bonded control die) · primary ▤ 🔎 multi-die packaging inside one qubit module (Zuchongzhi-3 platform); no inter-module interconnect
10 Manufacturing	Superconducting-qubit lithography (Al/AlOx/Al junctions, Nb wiring, 300 mm) · primary ◌ 🔎 Superconducting-qubit lithography (Nb/Al JJ, 300 mm) — IBM Albany 300 mm / Anderon foundry; Google Santa Barbara; Rigetti ABAA trimming (97.4% frequency-targeting success); OQC 500-qubit wafer-scale…

Standard records

2Q layers per syndrome round → 40 cycles · best (QEC cycles at d=7)

Dec 2025 · source

leakage per gate → 6.40e-4 · best in the field (leakage after 40 cycles, 72x suppression)

all-microwave LRU, no extra DC lines · Dec 2025 · source

SPAM error → 9.50e-3 · typical (readout error in a 300 ns window)

Dec 2025 · source

evidence: ✅ 7 / 13