Qubits from ion traps are characterized by particularly long coherence times, high gate qualities and high entanglement. With them, more complex calculations are possible than with short-lived and error-prone qubits. In addition, both their control systems and integration into microelectronics and microfabrication are mature. This makes them well suited for industrial production. All this makes ion traps an excellent basis for powerful quantum computers. However, there are also hurdles: They have to be heavily cooled and operated in a vacuum and require complex control by many lasers. This is currently still a scalability obstacle. And their characteristic stability also has a downside: ion trap qubits switch comparatively slowly, which partially offsets the advantage of long coherence times.
Significance for Germany
A lively, competitive environment has emerged in Germany for the production, classification and use of ion traps. Thanks to many research and qualification projects as well as advances in applications, ion trap technology has made great progress. This is especially true for quantum computing (ion traps are also suitable for other applications such as extremely precise atomic clocks). Together with NV centers, they are the most widespread hardware basis for German startups and companies. This makes ion traps one of the most promising systems in Germany.
Ion traps in the DLR QCI
We have commissioned five ion trap projects from German and European industrial companies. The reason for this is that not only are ion traps technologically advanced, but the industrial ecosystem fits. In the first batch, we are procuring a demonstrator system with 10 qubits, which should be available to DLR employees just one year after the start of the project. We are awarding the second lot twice: The goal is to build and operate a quantum computer with at least 50 fully functional qubits on a chip that is scalable and, in the future, error-correctable. We are also awarding the third lot twice: As an alternative to the chip design from lot 2, the focus here is on a modular design in which several chips are networked for a scalable architecture. In lots 2 and 3, usable complete systems should be available after four years.
All ion trap projects in the QCI
Legato: Prototype trapped ion quantum computer with four interconnected modules
TeufIQ: Technology development and support for ion-trap quantum computers
QSea II: Modular and scalable ion trap quantum computer
QSea I: Remote access 10-qubit ion trap-based quantum computer demonstrator
Xaphiro: Prototype trapped-ion quantum computer with at least 50 qubits
Toccata: Trapped-ion quantum computer with at least 50 qubits and error correction
Ion traps capture individual ions in an electrical field and use lasers to cool them down to a few millikelvins. The qubits are realized by different energy states within the hyperfine structure of the ion. This makes extremely long coherence times possible. Gate operations are implemented either by targeted laser pulses or by global microwave and magnetic fields. Finally, the state of the qubits is measured by optical transitions. In recent years there have been significant advances in the miniaturization of ion traps: This enables industrial production and innovative chip designs that contribute to scalability. We want to further advance and use this knowledge with the help of our orders.