Startups develop diamond-based quantum computers

Startups develop diamond-based quantum computers

Technology News |
By Christoph Hammerschmidt

Diamonds are a girl’s best friend – and they even can advance quantum computing. Two startup companies are taking a promising approach there.

One promising technology approach for quantum computing is the realization of qubits based on so-called nitrogen vacancy (NV) centers in the crystal lattice of diamonds. This approach is being pursued independently by the technology companies SaxonQ and XeedQ (both Leipzig, Germany). Now they received a major assignment from the German Aerospace Research Centre DLR.

Perfect diamonds consist of a flawless lattice of interconnected carbon atoms. A nitrogen defect is a disorder in this crystal lattice. It can also occur naturally. Diamonds with a particularly large number of nitrogen atoms are yellowish in color. Only synthetic diamonds are used for quantum computers. Nitrogen atoms artificially introduced into the crystal lattice replace carbon atoms on their lattice sites. When these nitrogen foreign atoms combine with an adjacent empty lattice site, NV centers are formed.

“Such qubits have the advantage of operating at room temperature. This significantly expands the potential range of applications for these quantum computers. Other systems, such as those with superconducting circuits, can only be operated at very low temperatures,” explains Dr. Robert Axmann, head of the DLR Quantum Computing Initiative (QCI). NV quantum processors are considered lightweight and mobile. In the future, their use is also conceivable in aircraft or satellites. That’s why the German Aerospace Research Center (DLR) is also showing interest in the Leipzig-based company’s technology and has now awarded them contracts worth a total of €57 million.

One of the biggest challenges currently facing this technology is to place several suitable NV centers a short distance apart. Only then can they be effectively entangled with each other, which is the prerequisite for a quantum computer.

SaxonQ and XeedQ: Similar goal, different approaches

SaxonQ, a spin-off of the University of Leipzig, generates the NV centers just below the surface of the diamond crystal using a proprietary technique. This approach promises high precision in the targeted arrangement of NV centers. XeedQ, on the other hand, arranges the NV centers in a three-dimensional structure in the diamond crystal, resulting in a mutual interaction. Together with a special readout method, this makes it possible to build a scalable quantum computer.

In a first phase of the DLR contract, a demonstrator system with at least four qubits is to be created promptly in each of the two projects – although this is too few for practical use, it demonstrates the practical feasibility of this approach. In later phases, the development to larger systems will take place: After four years, the goal is to build quantum computers with more than 32 qubits that are scalable and error-correctable. All systems will be integrated and operated in the laboratories of the DLR Innovation Center in Ulm.

Synergies with projects in Ulm and Hamburg

In Ulm and at the DLR Innovation Center Hamburg, there are close synergies with other projects in the DLR Quantum Computing Initiative. A call for proposals on spin-enabling technologies focuses on subsystems and assistive technologies for spin-based quantum computing. NV quantum computer manufacturers will benefit from the reproducible fabrication and characterization of the qubit hardware that is being worked on jointly.

“DLR is building a quantum ecosystem in which research, industry and startups complement each other. In doing so, the DLR Quantum Computing Initiative is pursuing different technological approaches in order to evaluate and use them for a wide range of applications. In this way, the advantages and disadvantages of different architectures for quantum computers can be researched,” says Dr. Karla Loida, project manager in the DLR Quantum Computing Initiative. Recently, DLR has already awarded contracts for the development of ion trap systems and photonic systems.

Within the framework of the DLR Quantum Computing Initiative, prototype quantum computers of different architectures will be built within the next four years. In addition, the associated technologies and applications will be developed. DLR is involving companies, start-ups and other research institutions to jointly drive the work forward.

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