Flying Qubits and Quantum Transistors – One More Piece in the Quantum Computing Puzzle

Developing components and systems for quantum information processing is a major task with a significant impact on the future of quantum computing. We are at a point where avid research is taking place in multiple directions; every little progress has the potential to shape the future of this industry. Within CEA Grenoble, Dr. Eleni Chatzikyriakou is working on simulating the operation of transistors, thus improving their functionality and performance. 

Along with efforts focused on building qubits and increasing their coherence time (the time spent by qubits in superposition), scientists all over the world are interested in the possibility of connecting qubits into complex circuits,  connecting multiple quantum devices, or developing hybrid devices, where both quantum and classical effects are harnessed simultaneously.

PHELIQS (Laboratoire PHotonique ELectronique et Ingénierie QuantiqueS) is a program developed within CEA Grenoble, aiming to find and test new solutions for creating devices that process quantum information. As a research fellow with a Ph.D. in Electronics and Computer Science and a strong interest in the quantum field, Dr. Eleni Chatzikyriakou contributes to this program by simulating the physical processes that take place in a quantum computer in order to find optimum designs that will improve transistor functionality.

In classical devices, transistors take care of the distribution of electric signals inside the machine. Similarly, a quantum transistor is meant to manipulate and transfer quantum information. However, due to the particularities of this technology, transistors have to function according to the principles of quantum physics as well. Even though some progress has been made, this technology is still in its infancy.

A way to transfer information between several quantum devices would be by using the so-called “flying (delocalized) qubits”. In this case, the quantum architecture would use stationary (localized) qubits to store data and perform computations. The information stored this way would then be transferred to a flying qubit, which will transport it to the next device and reconvert it into a stationary qubit.

“We are looking into technologies that incorporate various physical phenomena related to electrons, such as their spin or valley, or even delocalized electrons that take up more space but could be more robust than localized ones.”

Moreover, scientists within PHELIQS are also examining the possibility of performing logical operations on the qubits while they are being transmitted, making this channel more than just a means of data transport.

This process comes with multiple challenges, some of them relate to the accuracy of the transfer between a stationary and flying qubit, the flying qubit’s ability to preserve its coherence, and the distance it can cover. Like stationary qubits, scientists are testing different technologies to build flying qubits. One of the main questions is whether stationary and flying qubits could interact if they are built using various technologies, or if they must have a similar physical implementation.

Developing transistors and devices is a long and strenuous process, backed up by a lot of work on the theoretical level. Currently, most of the tests are carried out on classical computers, where various models are developed, evaluated, refined, and only then, applied in a laboratory setting.

Big players in the field of quantum computing have recently announced that they were able to perform operations faster than classical computers. However, this has also been questioned, as the decoherence of the qubits does not allow their number to increase beyond a certain threshold. Therefore, in some cases, classical computers are still faster than quantum devices. However, Dr. Chatzikyriakou remains optimistic that flying qubit technology can contribute to the robustness of the quantum devices.

When will we reach the next milestone in Quantum Technology?

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D. C. Glattli, J. Nath, I. Taktak, P. Roulleau, C. Bauerle,and X Waintal, Design of a single-shot electron detector withsub-electron sensitivity for electron flying qubit operation, arXiv:2002.03947

G. Fève, P. Degiovanni, and Th Jolicoeur, “Quantum Detection of Electronic Flying Qubits,” Physical Review B 77, no. 3 (January 8, 2008): 035308,

Quantum Computing, Quantum Tech, Quantum Transistors

Catalina Sparleanu

Working with top experts to identify how the latest innovations and disruptive technologies will impact businesses, industries, and society. I have an academic background in social science (Ph.D. in Sociology), an MBA degree, and experience in private companies and NGOs.

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