Atomic shells become computational building blocks
- The start-up planqc, based in Garching, near Munich, will construct quantum computers using neural atoms within three and a half years.
- A system with more than 100 qubits is being developed at the DLR Innovation Center in Ulm.
- planqc uses the interaction of atoms enlarged 1000 times.
- Focus: Quantum technologies, quantum computing, digitalisation
Neutral atoms, lattices of laser light, entanglements – the processing and memory components of quantum computers1* can be made from these. The more of these qubits2 that work without errors, the more powerful a quantum computer can be. Qubits made of neutral atoms3 are considered promising in this context. In order to advance the development of this technology, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) has awarded a contract. The start-up planqc, based in Garching, near Munich, will develop a quantum computer based on neutral atoms within three and a half years. The contract has a value of 29 million euros.
(*See glossary at the end)
Atoms – in contrast to charged ions – are electrically neutral. All atoms of the same isotope of an element have the same properties. planqc therefore uses them in their ‘ground state’ for quantum computing: "In order for the neutral atoms to become qubits, they must first be trapped and confined in a vacuum by laser beams," says Robert Axmann, Head of the DLR Quantum Computing Initiative (QCI). The atoms are then arranged regularly, similar to eggs in a carton, and can be manipulated with lasers. This is how individual qubits are created. "To have two qubits interact with each other, the atoms are excited into so-called Rydberg states. Without an interaction and entanglement4 between qubits, quantum computers do not work," Axmann explains.
In atoms in the Rydberg state, the outermost electron in the atomic shell is much further away from the atomic nucleus than normal. This makes the atoms a thousand times larger. In very simplified terms, this leads to a Rydberg atom ignoring neighbouring atoms and interacting with a more distant Rydberg atom beyond them. This is how atomic shells become the computational building blocks of quantum computers.
Development work in close proximity to DLR institutes and other start-ups
planqc is now creating a prototype quantum processor using this technology. It is to grow to a system with more than 100 qubits. The quantum computer is also to be scalable and, in the future, error correctable. This means that the number of qubits can be increased, and the system will work error-free. Error-proneness is considered one of the biggest obstacles in quantum computing.
planqc uses offices and laboratories at the DLR Innovation Center in Ulm for its development work. In the immediate vicinity of the DLR institutes, start-ups and companies here are already producing quantum computers based on nitrogen vacancies5 in diamond, photonic quantum computers6, hybrid systems with analogue computers and spin qubits7 on behalf of the QCI. At the second DLR Innovation Center in Hamburg, research is being conducted on quantum computers based on ion traps8. The application process for solid-state quantum computers ended recently.
“Diversity is an important feature of the DLR Quantum Computing Initiative. The QCI pursues different technological approaches to investigate their respective advantages and disadvantages. With this project, we are adding another promising technology to our quantum computing portfolio at the Ulm site,” says Karla Loida, Hardware Lead for the QCI. It is not yet clear which architectures for quantum computers will prevail. Some are already relatively advanced, such as superconducting9 systems, but these need extremely low temperatures. There are other systems that could be considered for quantum computers, but which have not yet been explored in depth.
The DLR Quantum Computing Initiative
The DLR Quantum Computing Initiative (QCI) is constructing prototype quantum computers with a number of different architectures. It is also developing the associated technologies and applications. DLR involves industry, start-ups and other research institutions to jointly advance the work and establish a quantum computing ecosystem.
DLR has been provided with resources by the Federal Ministry for Economic Affairs and Climate Action (Bundesministerium für Wirtschaft und Klimaschutz; BMWK) for four years and awards contracts to companies on a large scale. DLR contributes its own expertise and capabilities to the research and development process and focuses on transfer to industry.
Fast calculations with quantum bits
Quantum computers are an important technology for the future. They can perform calculations and simulations in specific fields of application much faster than conventional supercomputers. Their use is possible, for example, in the transport and energy sectors, but also in fundamental research or the operation of satellites. Quantum computers exploit quantum mechanical effects10 such as entanglement and superposition11. Their quantum bits (qubits) can assume the states 0 and 1 simultaneously – and not just one at a time, like conventional computers. This in turn is what makes quantum computers so powerful. At DLR, several institutes are working with quantum technologies. There is also a great need at DLR to conduct research on and with quantum computers in the future. The potential of quantum computing is one of the fundamental and pioneering areas of expertise needed to ensure that the German economy continues to occupy a leading position internationally.
planqc GmbH (Garching, near Munich, Bavaria)
The technology company planqc was founded in 2022 by a research team from the Max Planck Institute for Quantum Optics and the Ludwig Maximilian University of Munich. planqc builds quantum computers that store information in individual atoms. The qubits are arranged in highly scalable arrays and manipulated with precisely controlled laser pulses. planqc is the first start-up to emerge from Munich Quantum Valley.
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Glossary
- Quantum computer: Novel form of computer that works on the basis of the laws of quantum physics. Its quantum bits (qubits) can not only assume the states 0 and 1, but also intermediate values. Quantum computers have the potential to solve certain tasks that classical computers are not able to.
- Qubit: Qubits (quantum bits) are the smallest computing and storage units of a quantum computer, based on the laws of quantum mechanics. In contrast to the classic bits of conventional digital computers, which can only have states 0 and 1, qubits can assume an infinite number of intermediate values. Two-state quantum systems at the atomic level (for example atoms, ions or light quanta) or in solids (for example in semiconductors or superconductors) serve as qubits.
- Neutral atoms: Neutral atoms – unlike ions – are electrically neutral. For quantum computing, they are trapped individually using methods such as optical lattices. The properties of each atom are the same as those of the other atoms (of the same element adn isotope), which means that a large number of atoms can be controlled without calibration.
- Entanglement: In quantum physics, entanglement refers to the interdependance of individual states of an overall system. In a quantum computer, this means that one qubit has information about the state of another qubit, and manipulating one qubit affects the state of the other.
- Nitrogen-vacancy centre: A nitrogen-vacancy centre is a defect in the carbon crystal lattice of diamond consisting of a single nitrogen atom and a neighbouring carbon vacancy. NV centres can be used as a single-photon source or in quantum computers. Electron spins in the NV centre and the surrounding nuclear spins are used as qubits for the latter purpose.
- Photon: A massless, electrically neutral elementary particle. Light consists of photons. A photon is released, for example, when an electron in the atomic shell changes to a lower energy state.
- Spin-Qubits: Spin-Qubits sind Festkörperspins, die zur Realisierung von Quantencomputern genutzt werden. Hierbei können als Qubits sowohl Kernspins als auch Elektronenspins verwendet werden. Dabei handelt es sich um die Drehimpulse von Atomkernen und Elektronen, die sich in einem Magnetfeld ausrichten und manipulieren lassen.
- Ion trap: System of electromagnetic fields that spatially fixes charged atoms (ions). Ion traps are used for the implementation of quantum computers in which an ionised atom represents a quantum bit that is controlled and manipulated in the ion trap.
- Superconductor: A material that can conduct electricity with almost no resistance at extremely low temperatures. The superconducting ability occurs below this very low transition temperature. Superconducting circuits represent one approach for the implementation of quantum computers.
- Quantum mechanics/quantum physics: Branch of physics in which physical processes are described in the world of the very smallest objects, at the atomic level.
- Quantum superposition: In quantum mechanics, superposition means that a quantum physical object exists in several different states at the same time.