ETRI 8-photon silicon-photonic qubit chip

ETRI (with KAIST and the University of Trento) · photonics · DEMONSTRATED (chip level) (Nov 2024) · 8 physical qubits · access: lab-only

qubit type: path-encoded (dual-rail) photonic qubit

gate mechanism: linear-optic quantum gates formed by about half of the on-chip switches (probabilistic linear-optical entangling)

connectivity: programmable switch mesh routing photon paths

control: on-chip optical switch drive (switch technology not stated)

control placement: room-temp

readout: single-photon detectors (type not stated)

gate evidence: no published figure

flags: no published error rates

1 Qubit carrier	Single photon (discrete variable) · primary ▨ ✅ single photons from 8 on-chip photon sources; 8 photons controlled on one chip
2 Encoding	Dual-rail (erasure) encoding · primary ▨ 🔎 path-encoded qubits: a 4-qubit circuit uses 8 propagation paths, i.e. two paths per qubit
3 Gate mechanism	Linear-optical fusion (heralded) · primary ▨ 🔎 about half of the ~40 switches act as linear-optic quantum gates; 6-qubit entangled state generated
4 Connectivity / transport	Photonic switching / routing (electro-optic, feed-forward) · primary ▨ ✅ ~40 on-chip optical switches set the photon propagation paths
5 Control	Electro-optic drive + feed-forward electronics (room temperature) · primary ◌ 🔎 room-temperature drive of the on-chip switches; drive technology not described
6 Readout	Single-photon detection (SNSPD / TES) · primary ▨ ✅ final states measured with highly sensitive single-photon detectors
7 Code	— none — nothing in this layer ◌ 🔎 no QEC code; multiphoton state generation and interference experiments
8 Decoder	— none — nothing in this layer ◌ 🔎 no decoder; no QEC run
9 Interconnect	— none — nothing in this layer ◌ 🔎 single 10 mm x 5 mm chip; no fibre link between modules
10 Manufacturing	Photonic IC foundry (SiN, BTO, TFLN, SNSPD on 300 mm) · primary ▨ ✅ silicon-photonic integrated-circuit chip with sources and switches on one die

evidence: ✅ 4 / 10