Photonic Quantum Computing

Photonic qubits have many advantages: The generation, control and measurement of photons as quantum systems is routine. With the help of light guides and optical paths, they bridge large distances as “flying qubits”. And thanks to the many advances in the manufacture of integrated optical components, photonic quantum computers fit on a single chip. However, they have one major disadvantage: photons do not interact with each other. Photonic quantum computers have to work around this problem in a complex manner, which has long been an obstacle. To advance the development of this technology, we rely on measurement-based photonic quantum computing as a promising platform and guarantor of quickly usable quantum computers.

Photonic quantum processor with cooling | Photo: QuiX Quantum, Daniël Verkijk

Significance for Germany

In photonics, Germany traditionally has a strong research and industrial base as well as a significant supplier industry and many small and medium-sized companies and start-ups for enabling technologies. Several German and European startups are developing quantum processors. Nevertheless, photonic quantum computing is less developed than other approaches. We expect this to accelerate technology transfer.

Our photonic projects

DLR QCI has placed an order for the development of a universal quantum processor based on photonic circuits: the contractor will implement more and more input modes and photonic qubits in several phases. After three years, the contractor will develop a demonstrator with eight photonic qubits and within four years a system with at least 64 qubits. The winner of the tender, the company QuiX Quantum, will integrate the photonic quantum computer at the DLR Innovation Center Ulm.

Photonic quantum processor | Bild: QuiX Quantum, Daniël Verkijk

All photonic quantum computing projects


Photonic quantum processor | Photo: PHIX BV

Technical implementation

Photonic quantum computers calculate by sending photons through a course of optical elements that represent the algorithm. The approach is elegant. But because photons do not interact with each other, photonic systems have long been considered unsuitable, despite their many advantages. One of several solutions to this problem is the creation of so-called cluster states: associations of many entangled photons.

We pursue this measurement-based approach with our photonic quantum computer. It can also be used to realize two-qubit gates, i.e. the basis for more complex quantum calculations. In addition to the application in quantum computers, photonic systems are also suitable for use in quantum cryptography and quantum communication – other important applications at DLR. This possible amalgamation of calculation and communication on a common technological basis makes photonic systems particularly attractive, and not just for us.


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