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Quantum state transduction in a hybrid spin-opto-mechanical system

Carlsbergfondets internationaliseringsstipendier

What

Modern communication and information technologies rely heavily on the use of transducers - devices which enable conversion of signals between different physical modalities (e.g. conversion between electrical and optical signals). However, with the rapid progress in quantum computing, communication and sensing, where the laws of quantum physics can be exploited to tackle problems beyond the reach of existing technologies, a markedly different type of transducers needs to be developed, capable of handling fragile quantum signals. This project seeks to develop such a quantum transducer, and study the interactions between optical, mechanical and electronic (i.e., electron spin) modalities in a regime where single quanta of information are shuttled between them.

Why

To fully harness the potential of quantum computing, an interconnected network of quantum devices is necessary. Today's leading contenders for quantum computers are based on superconducting electronic circuits, and connecting them over large distances will require efficient conversion between microwave and optical signals, since light can travel over vast distances with little attenuation. A number of proposed interconnect architectures rely on the use of phonons (quanta of vibrations) as information carriers at the nodes of the network, due to their ability to interact with a wide range of quantum systems. Therefore, understanding how phonons interact with electronic and optical degrees of freedom in a quantum device, and engineering these interactions is of significant importance.

How

The transducer at the heart of this project will be based on silicon carbide (SiC), a widely used semiconductor material in the high-power electronics industry. In addition to having excellent optical and mechanical properties, SiC also hosts a family of defects in its crystal structure, which act as artificial atoms. Importantly, the electron spin of a single defect can be used as a quantum bit (qubit), the state of which can be measured by optical means. Performing high-fidelity measurements of the qubit and, in parallel, of a vibrational mode of the device, constitute some of the first steps in this project. These will allow us to study the influence of vibrations on the qubit state and vice versa, and ultimately demonstrate quantum transduction between a spin qubit and mechanics.

SSR

While several aspects of this research project can aid our understanding of fundamental physics, the outcomes of the project also hold the potential for breakthroughs in quantum communication, sensing and information technologies. Quantum computing at large is expected to revolutionise several existing industries, with prospective applications ranging from drug and vaccine design, tackling of energy consumption and distribution problems, to "unhackable" new communication methods, secured by the laws of physics. We can therefore expect the emergence of this new technology to have a tangible impact on our society.