Photonic quantum computing
Qubits made of light — room temperature, and built to manufacture.
Photonic approaches encode quantum information in particles of light and process it with optical chips. Photons barely interact with their environment, so they can run at (or near) room temperature and travel through fibre — a natural fit for quantum networking. The bet is that photonics is the most manufacturable route to a million-qubit machine.
In plain terms
If other qubits are delicate ice sculptures that must be kept frozen, photons are beams of light bouncing through a hall of precisely angled mirrors. Nothing to keep cold — the challenge is making the light interact on demand.
How it works
Information rides on properties of photons (path, polarization, timing). Chips route them through interferometers — networks of beamsplitters and phase shifters — to perform gates.
Because photons rarely interact, two-qubit gates rely on measurement and clever schemes (measurement-based / fusion-based computing), plus very good single-photon sources and detectors.
The upside is manufacturability on semiconductor lines and easy networking over fibre; the challenge is photon loss and building deterministic gates at scale.
The problem it solves
Photonics targets large-scale, fault-tolerant machines by leaning on existing chip foundries, and is the natural technology for the quantum internet — linking processors and enabling secure communication.
- +Operates at or near room temperature — no dilution fridge.
- +Manufacturable on standard semiconductor processes.
- +Photons move through fibre — ideal for networking.
- –Photon loss accumulates and is hard to correct.
- –Deterministic two-qubit gates are difficult; often measurement-based.
- –Long-horizon: fewer incremental cloud products today.
Companies building this
Manufacturing-first bet: build a million-qubit fault-tolerant machine on a commercial semiconductor foundry.
Photonic hardware plus the open-source PennyLane framework for quantum machine learning.
High-quality single-photon sources — a key bottleneck — packaged into full photonic systems.