Colour-centre spins — network nodes (NV/SiV/T) on the map bar: Spin–photon nodes

The architecture in the report (§8.3)

8.3.15 Spin–photon nodes — Colour-centre spins — network nodes (NV/SiV/T) (defect)

The idea. A point defect in diamond (NV, SiV, SnV) or silicon (T centre) (defect) has a spin-selective optical transition: its electron spin emits a photon entangled with it, and nearby nuclear spins under hyperfine-conditional microwave gates (g_mwspin) keep a small memory. Heralded photons (ic_spinphoton), not on-chip wiring, join these few-qubit nodes. Table 8.3's bet fuses two on one carrier: a room-temperature NV accelerator and cryogenic network nodes. Both forgo a dense lattice; for the nodes, link rate, not gate error, is the clock.

What it needs. The own technologies require the carrier — gates its spin register, fluorescence readout its optical transition, the link its spin–photon interface — and the carrier requires a host crystal, whose only technology is diamond (fab_diamond). Five technologies are borrowed: encoding, readout, baseband control, nearest-neighbour lattice, qLDPC code. Two clash: the code conflicts with the lattice, needing degree-6 checks that here only the optical link supplies. No decoder (§7.6): a code named, none decoded.

Where it stands. Five machines, five devices, no two-qubit error (Table 8.3). The largest, QC2026 Dual Core (SaxonQ, 10 qubits on two five-qubit NV cores), ran under operating conditions at Hannover Messe in April 2026 — a mobile room-temperature system with no published error rates [P][364]; SaxonQ's four-qubit SXQ4 units are delivered (DLR, Fraunhofer IWU) [C][880]. Quoll / QB-QDK 2.0 (Quantum Brilliance) is deployed: 6 qubits in the register, room-temperature units at Oak Ridge, no gate fidelity [C][278]. Entanglement First modules (Photonic Inc, QBI Stage B [65], [66]) teleported a state into a remote matter node over 30 km of commercial fibre (February 2026), no rate or fidelity [P][279]. Fujitsu's Diamond-spin quantum computer prototype carries SnV centres on photonic circuits at −271.6 °C, no qubit count or fidelity, multi-module by 2027 [C][R][210]. Per-node figures: NV gate errors below 0.1% [P], SiV entanglement over 35 km at ~1 Hz [D], a post-selected T-centre teleported CNOT [P] [208], [209].

Exceptions and borrowings. All three fit here best; none fits whole. Photonic connects any-to-any through the optical link (∅G-optlink), which its SHYPS qLDPC code needs, claimed at 20× fewer physical qubits per logical [C][280]; its silicon host has no technology (∅G-sicolour): layers 4 and 10 are drawn too narrowly. Quoll lacks link, code and decoder, and its microwave-and-laser control has no technology (∅G-nvroom): a processor on a network architecture, drawn too widely. Fujitsu's prototype adds a photonic-IC foundry (fab_pic), states no connectivity and shares the control gap at 1.55 K: an early hybrid. Only Photonic uses the namesake link; the architecture's spin gates (g_mwspin) recur as the layer-3 alternate of the quantum-dot and donor architectures.

The next test. By the technology briefs (§5.2 has no defect row), confirmation by March 2028 is an unconditional inter-node gate above 90%, a heralded link above 1 kHz, or link rate and fidelity from Fujitsu's multi-module prototype. Demotion: Photonic's links still without rate and fidelity, and the SnV modules without a qubit count, at end-2027; then the network bet is repeater and sensing technology; Quoll needs its own architecture.

What the builders say. Fujitsu, with TU Delft and QuTech, built a working diamond-spin prototype with tin-vacancy centres on photonic chips [C][210], chose the route for its optical links between modules and plans a multi-module prototype by 2027 [R][210]. Photonic argues that T-centre spin qubits in silicon, linked by light, give high connectivity, efficient error correction and a fit with telecom networks [C][866]; in 2024 it ran a teleported CNOT between qubits in different cryostats [C][867]. Quantum Brilliance bets on nitrogen-vacancy qubits at room temperature and pressure, which its CEO says decides where the machines can go and who can use them [C][868]; Fraunhofer IAF bought its rack-mounted QB-QDK2.0 [C][869].

Machines of this architecture (register: 5, of them 5 devices, 5 gate-capable). SaxonQ — QC2026 Dual Core (demonstrated, 10), SXQ4 (deployed, 4); Fujitsu (with TU Delft and QuTech) — Diamond-spin quantum computer prototype (demonstrated); Photonic Inc. — Entanglement First modules (demonstrated); Quantum Brilliance — Quoll / QB-QDK 2.0 (deployed, 6).

Cells outside the architecture's slots (7). Diamond-spin quantum computer prototype: L4 undisclosed where the architecture expects a technology; Diamond-spin quantum computer prototype: L5 ∅G-nvroom (Atlas gap — light, microwave and RF control of SnV spins; module operated at -271.6 °C (1.55 K)); Entanglement First modules: L4 ∅G-optlink (Atlas gap — any-to-any optical link used as the connectivity layer, not only as interconnect; basis fo); Entanglement First modules: L10 ∅G-sicolour (Atlas gap — Si-28 T-centre + silicon-photonics co-fabrication; no foundry node published; fab_diamond ); Quoll / QB-QDK 2.0: L5 ∅G-nvroom (Atlas gap — room-temperature microwave drive + green-laser initialisation + optical readout; no cryoge); QC2026 Dual Core: L5 ∅G-nvroom (Atlas gap — room-temperature optical initialisation and microwave control from a standard wall outlet,); SXQ4: L5 ∅G-nvroom (Atlas gap — optical initialisation and microwave gates at room temperature (18–27 °C), mobile, no cryo).