Editorial Feature

New Cryogenic On-Wafer Prober for Quantum Material Characterization

Quantum technology is rapidly emerging as a disruptive form of innovation. A new, automated characterization device introduced by Fraunhofer promises to lift solid-state qubit generation to the next rung on the ladder of quantum technology advancement.

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Devices produced by using the principles of quantum mechanics constitute quantum technology. Quantum technology is currently being developed focusing on four different applications. These applications are computing, sensing, communication, and simulations.

The fundamental unit of data in quantum devices is called a qubit. There are different experimental platforms from which these qubits are generated. These platforms can range from cold atomic qubits, trapped ion qubits, solid-state qubits such as quantum dots and can also be superconducting qubits.

Properties of Quantum Devices

The performance of any quantum device depends on how well the qubits are isolated from environmental intervention. Some of the bigger challenges in the development of quantum technology rely on generating high-quality qubits that can be isolated from exterior interferences such as vibrations or thermal drifts. For solid-state qubits such as quantum dots, the fabrication process can also pose some challenges.

To reap the predicted benefits of quantum technology, many qubits have to be connected through quantum entanglement, scaling up the number of operational qubits.

In most qubit platforms, to extract the quantum mechanical properties, the qubits are maintained at very cold temperatures. In most cases, the temperature is less than 2 degrees kelvin - in atomic platforms it can go down to micro kelvins!

When controlling qubits like those generated from quantum dots, the fabrication method produces a characteristic randomness. This is an outcome that requires repeated single measurements to qualify and select the right candidates to develop devices. This exercise takes time and slows down the process of scaling.

Cryogenic On-Wafer Prober

The Fraunhofer Institute for Applied Solid State Physics IAF has introduced a new machine, the cryogenic on-wafer prober, capable of characterizing many wafers in a single measurement. Solid-state qubits are fabricated from appropriate materials in the form of wafers. The advantage provided by multiple wafers characterized in one measurement is that it enables faster identification of correct samples to use.

The newly installed cryogenic on-wafer prober can operate at cryogenic temperatures below 2 K (271.15 C). A high volume of up to 25 wafers in a row in industrial sizes of 200 nm and 300 nm can be fully characterized by the instrument.

At temperatures close to absolute zero (-273.15 °C), the functionality of qubits based on semiconductor quantum dots and quantum wells, as well as superconductors, increase. This is due to reduced outside interference, the threshold for superconductivity is reached and makes it possible for qubits to be developed and entangled. Qubits must therefore be characterized at their operational temperature, and a statistically evaluable collection of measurement data must be gathered in order for testing, optimization, and scaling to be successful.

The research efforts at the Fraunhofer Institute for Applied Solid State Physics IAF are hoping to gain a deeper understanding of the operation of quantum instruments based on semiconductor quantum dots, quantum wells, and superconductors using the cryogenic on-wafer prober. Access to statistically significant data sets from the wafer prober can be used to systematically improve and scale the manufacturing of qubit devices.

The data sets obtained greatly lessen the single measurement-specific dependence on random hits. In this approach, the development of dependable manufacturing of high-quality qubits that may be employed in quantum computers and quantum sensors is facilitated by the growth of measurement capacity at the institute.

This characterization gap is closed by the cryogenic on-wafer probe. The amount of data accessible is increased by automated measuring of industrial-size wafers at appropriate cold temperatures with a quick switching time. This information gives scientists and engineers the foundation they need to enhance qubit-formation devices specifically and scale them up.

Future Outlook

The cryogenic wafer prober was developed as part of the KryoproPlus project, a significant accomplishment in the field of quantum investigation. The facility is the second in Europe and the first in Germany of its sort, and it is the fifth of its kind globally.  The installation was supported by the German Federal Ministry of Education and Research (BMBF). This cutting-edge facility  has been commissioned to  support a further three ground-breaking projects. These are "QUASAR — Pioneering Semiconductor Quantum Processor with Scalable Shuttling Architecture," "MATQu — Exploring Quantum Materials," and "QLSI — Revolutionizing Large-Scale Quantum Integration with Silicon."

In order to enable scaling and industrial production of qubits for Europe and worldwide, it is crucial to better understand how to obtain good, homogeneous qubits.To do that, the qualitative view of device behavior must be widened to include a quantitative, statistical viewpoint. The initiatives surrounding the development of the Cryogenic wafer prober represent significant steps forward as we continue to explore the fascinating world of quantum computing.

More from AZoQuantum: What are Quantum Cascade Lasers?

References and Further Reading

Dargan, J. (01 September 2023) Cryogenic On-Wafer Probing For Assessing Qubit Device Quality In Quantum Computing & Sensing. [Online] Quantuminsider.com. Available at: https://thequantuminsider.com/2023/09/01/cryogenic-on-wafer-probing-for-assessing-qubit-device-quality-in-quantum-computing-sensing/#:~:text=This%20innovative%20on%2Dwafer%20prober,low%20temperatures%20below%202%20Kelvin

Press Release. (31 August 2023) Cryogenic on-wafer prober determines quality of qubit devices for quantum computing and quantum sensing. [Online] IAF.Fraunhofer.de. Available at: https://www.iaf.fraunhofer.de/en/media-library/press-releases/cryogenic-on-wafer-prober-determines-qubit-quality.html

Sivarajah, I. (16 December 2021) Building Quantum Networks to Connect the World.[Online] AZoQuantum.com. Available at: https://www.azoquantum.com/Article.aspx?ArticleID=262

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Written by

Ilamaran Sivarajah

Ilamaran Sivarajah is an experimental atomic/molecular/optical physicist by training who works at the interface of quantum technology and business development.


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