In the realm of nanoscience and quantum technologies, the search for new materials with superior physiochemical, electrical, and thermal properties is ongoing. One such material which has received intense attention since its discovery in the early 2000s is graphene.
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What is Graphene?
Following its discovery in 2004, graphene has continued to be a hot topic of scientific research.
While its discovery, isolation, and investigation are credited to Nobel Prize winners Andre Geim and Konstantin Novoselov, its existence was theorized for decades previously.
Its remarkable properties, such as high electrical conductivity, flexibility, and strength, have ensured that graphene has become a key target of research within several fields, including energy storage, medicine, wearable technologies, fashion, and electronics.
Some of the favorable properties of graphene include strong absorption of all wavelengths of light and efficient electrical and thermal conduction along its plane. While graphene strongly absorbs light, the thinness of a single sheet of graphene renders it transparent. Furthermore, graphene is theoretically the strongest material known to science.
Besides its 2D form, bilayer graphene, which comprises two layers of graphene, produces a material with exceptional mechanical, electrical, and optical properties. This form of graphene has emerged as a particularly notable material in several research fields.
Graphene in the Field of Quantum Research
While graphene has potential applications in many industries, one of the most intriguing and innovative emerging areas of graphene research is its use in quantum technologies.
Graphene has been explored for its applications in multiple areas of quantum research, from quantum computing to graphene-based nanodevices. Graphene quantum dots (GQDs,) for instance, have been used in research into efficient energy storage and conversion applications and optical and electrochemical biosensors.
Bilayer GQDs possess unique chemical and physical properties, which make them attractive targets for quantum computing due to their near-perfect electron-hole symmetry. This symmetry allows quantum computers to possess robust read-out mechanisms, which is a core criterion for these devices.
Further Exploring GQDS in Robust Quantum Computing Devices
Research into bilayer graphene-based GQDs was published recently in the journal Nature. Scientists from the Netherlands were investigating how to realize robust semiconductor spin qubits. Such a development would help to realize large-scale quantum computers that could help solve some of the most profound research problems.
In 2022, researchers at QuTech, which also conducted the research in this latest paper, announced the development of the first silicon-based spin qubits. In total, six were created by the research team. Although graphene-based spin qubits hold vast potential, the authors have stated that there is still some way to go.
One of the most exciting potentials of bilayer GQDs is that both electrons and holes could be captured by the same gate structure, which would potentially revolutionize semiconductor technologies. In the latest research, the team created a “double” quantum dot, each housing a nearly perfectly mirrored electron and hole.
The research team has stated that their research could have implications for the development of robust and efficient hybrid systems for use in topological quantum computers.
Graphene-based Topological Qubits
Topological qubits are less error-prone to environmental factors than other qubit designs, giving them more stability and reliability. Research into this type of qubit is in its infancy, though graphene has emerged as a candidate for their realization.
Its ability to host “zero-energy modes” at its edges is one of the most intriguing properties that makes graphene an attractive prospect in topological qubit research. Quantum information can be stored and manipulated in these modes, facilitating a robust quantum computing platform.
Other research has incorporated graphene with other semiconducting materials, producing hybrid qubit systems. Graphene can also improve other aspects of quantum computing, such as highly-efficient single photon-detecting photodetectors.
Exploring the Potential of Graphene for High-Speed Read-Outs and Accurate Qubit State Measurements
A recent breakthrough was announced by researchers from Japan using graphene to improve high-speed rf reflectometry read-out techniques for nanodevices.
One of the key roadblocks to applying bilayer graphene to quantum computing is the accuracy of quantum bit state measurements. Even though there has been a lot of research into achieving this using low-frequency electronics, quantum computing demands faster and more efficient systems to measure dynamic electrical states.
The breakthrough was the use of microscale graphite (3-dimensional graphene) back-gates. Combined with a substrate made from undoped silicon, the team demonstrated a highly accurate quantum bit state measurement system that has good potential for use in quantum computers.
Here, we offered a brief introduction to some of the current research into graphene in the field of quantum science and technology. Although in its infancy, this field of quantum and nanotechnology research is highly promising, with the potential to realize robust, efficient, and highly accurate next-gen quantum computers.
References and Further Reading
Banszerus, L., et al. (2023). Particle–hole symmetry protects spin-valley blockade in graphene quantum dots. Nature 618 pp. 51-56 [online] nature.com. Available at: https://www.nature.com/articles/s41586-023-05953-5
Frąckiewicz, M. (2023). Graphene and Quantum Computing: A Match Made in Heaven. [online] TS2. Available at: https://ts2.space/en/graphene-and-quantum-computing-a-match-made-in-heaven/
Johmen, T., et al. (2023). Radio-Frequency Reflectometry in Bilayer Graphene Devices Utilizing Microscale Graphite Back-Gates. Physical Review Applied, 20, p. 014035 [online] journals.aps.org. Available at: dx.doi.org/10.1103/PhysRevApplied.20.014035