On the track to quantum computing: Higher scalability of superconducting qubits

Quantum computers are expected to easily solve tasks that even today's super computing centers fail at. But there are still a number of challenges to overcome before these computing geniuses can actually be used in broad applications. As part of Munich Quantum Valley, researchers at Fraunhofer EMFT are working to push the transfer of quantum technologies to industry.

© Fraunhofer EMFT/ Bernd Müller
Resonators for material analysis for superconducting qubits on 200 mm wafers with Nb coating

One focus of the activities is to optimize the scalability and stability of superconducting qubits. Qubits are the basic units of a quantum computer and consist of a Josephson junction - a superconductor-nonconductor-superconductor junction, set with high precision in the qubit circuits - and a resonator.

They are able to superpose for a period of time, known as the coherence time, and thus adopt all possible states simultaneously. This allows the quantum computer to calculate all possible solution paths simultaneously, which drastically increases the processing speed. However, the quantum computer can only process within this time frame. In order to improve the coherence time and keep it stable over as long a period as possible, the researchers are focusing on the greatest possible homogeneity in manufacturing. The more finely tuned the individual components are to each other, the longer the achievable coherence time. Improved coherence time of superconducting quantum circuits is considered a crucial pre-condition for the successful industrial operation of quantum computers.

Another challenge is to minimize the noise that occurs in current quantum computers, which can lead to a high error rate in calculations and significantly reduce the performance. The problem: Individual qubits are extremely vulnerable to noise, as they are subject to thermal, electromagnetic and even cosmic interference and phenomena that lead to noise and thus computational errors. To compensate these interferences, as many qubits as possible have to be interconnected on a chip as close together as possible, while still not interfering with each other. At the moment, the limit here is nine qubits. The research team at Fraunhofer EMFT is pursuing the approach of interconnecting significantly more qubits than before by means of space-saving design using through silicon vias (TSV) through the 200mm silicon wafer.

Munich Quantum Valley is funded by the State of Bavaria.

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Strategic Research Topic: Microelectronics for Quantum Technologies

Research Area: Micro- and Nanotechnologies


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Alexandra Schewski, doctoral student at Fraunhofer EMFT, on the exciting possibilities of 3D integration for superconducting quantum hardware.

Munich Quantum Valley (MQV)