Light Bridges for Quantum Computers ✛ ✎ ✦

Original: "Scalable Quantum Computing with Optical Links"
arXiv:2505.00542v1 · 2025-05-01 · arXiv non-exclusive · independent analysis · 1 min
You can connect quantum modules with light even using imperfect converters.

Modern quantum processors based on superconductors live only in bulky refrigerators at ultralow temperatures. Otherwise, thermal noise destroys their quantum nature — scientists call this quantum decoherence. One such fridge holds only a handful of qubits, but serious computing needs millions. The solution is to connect the fridges with light through fiber optics, which can carry quantum information. But inside, qubits talk in microwaves, while fiber optics only understand optical signals. So you need a translator, and current prototypes work like a bumbling moonshiner: they distill the microwave "mash" into photonic "liquor", but the output is a murky noise.

The solution resembles the art of distillation. Physicists devised a protocol where qubits from different modules try to establish quantum entanglement again and again. Each attempt is checked with a quantum measurement. Noisy, failed cycles are simply discarded, and several partially pure ones are repeatedly "distilled" together — just as raw alcohol is distilled into a pure product. After a few iterations, the connection fidelity rises to 99% — above the threshold needed for reliable quantum computing.

Ordinary fiber optics, which carry the internet today, can transmit single photons over hundreds of kilometers without noticeable signal loss — this is what makes the idea of quantum networks real.

The bottom line: there's no need to wait for perfect translators. Right now, we can build distributed quantum systems where dozens of simple fridges combine into a machine with millions of qubits, using existing technology.

Ordinary fiber optic cables can transmit single photons without significant attenuation over hundreds of kilometers — that's what the idea of quantum networks is built on.

C_{EO} = \frac{4 G_{EO}^2}{\kappa_{MW} \kappa_O} \approx 1
The cooperativity of the electro-optic interaction—a balance between coupling strength and resonator losses. A value around unity yields maximum conversion efficiency from microwaves to light.
Scientists
Erwin SchrödingerHugh Everett IIIStephen HawkingJacob BekensteinAbner ShimonyAlain Aspect
Concepts
scalable quantum computer scaling quantum computing technology data center optical switch optical computer medicine superconducting qubit hybrid algorithm cryogenic microwave measurement fiber optics complexity classical limit logical qubit memory computational cost supercomputer coupling transmon error propagation