Quantum Expert Insights
Photonic Quantum Computing—Why Isn’t It More Mainstream Yet?
Photonic quantum computing has all the ingredients for success: room-temperature operation, inherent noise resistance, and compatibility with existing fiber optic infrastructure. Yet it remains overshadowed by superconducting and trapped-ion approaches. The reasons reveal the tough realities of building practical quantum systems.
The core challenge is deterministic entanglement generation. Unlike trapped ions that reliably entangle when zapped with lasers, photons interact weakly—creating the needed quantum correlations requires complex setups with nonlinear optical materials or probabilistic heralding techniques. Xanadu’s Borealis processor demonstrated 216 squeezed-light qubits, but most photonic systems still struggle with the scalable creation of entangled states on demand.
Another bottleneck: single-photon detection efficiency. Even the best transition-edge sensors miss about 5% of photons, and these errors compound rapidly in deep circuits. While error mitigation helps, it eats into the purported speed advantages. Compare this to superconducting qubits with >99% gate fidelities, and the performance gap becomes clear.
The control problem is equally daunting. Photonic qubits (typically encoded in light’s polarization or time bins) require precise, stable interferometers—any vibration or thermal drift ruins computation. This makes photonic quantum computers look more like delicate lab equipment than rack-mountable servers.
Yet the field is quietly making strides. The UK’s ORCA Computing and France’s Quandela are commercializing photonic systems, while PsiQuantum’s ambitious fiber-based approach promises error-corrected scalability. Recent breakthroughs in integrated photonics and quantum dot light sources suggest the technology might follow a similar trajectory as classical integrated circuits—starting clunky before becoming ubiquitous.
The killer app may come from hybrid architectures: using photons to link distant matter-based qubits. This would leverage photonics’ natural strength—long-distance entanglement distribution—while sidestepping its computational weaknesses. Until then, photonic quantum computing remains a dark horse contender rather than the mainstream favorite.