Strong coupling and coherence in hybrid solid state quantum systems

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In the last half century of human history we have seen an incredible revolution in our ability to process and disseminate information, with the rise of computers, high speed communication networks, and the internet. The pace of progress is still extremely high, but a major challenge is on the horizon, as the size of processing devices shrinks to approach the scale of single atoms. At such tiny length scales, the physics governing the operation of electronic devices changes fundamentally to obey the laws of quantum mechanics, and computer processors could no longer operate in the conventional way that they do today. This approaching horizon is both a challenge and an opportunity. It has now long been known theoretically that quantum mechanics can in fact be used to carry out computing and communication in ways that are impossible with 'classical' systems, and a large research effort is now underway across many scientific disciplines to realize such quantum communication and computation in a practical way.In this fellowship, a variety of promising candidate systems for use as quantum bits (qubits) on future quantum electronic chips will be brought together and investigated in a truly quantum coherent manner. Static qubits made from superconducting electric circuits, and electrons trapped in islands on semiconductor chips will be coupled to 'flying' qubits in the form of quanta of light (photons) and quanta of vibrational motion (phonons) on electronic chips cooled to their lowest quantum mechanical energy state at close to absolute zero. The research will address key questions of how long the fragile quantum nature of information can last in such systems, how the different systems can be made to interact and exchange quantum information, and how they can be brought together to ultimately form the basic building blocks of future quantum computers, such as quantum logic gates and quantum memories.A particular focus of the research is to explore the potential of a system known as cavity QED in which the interaction between atoms (or static qubits) and light (or flying qubits) is enhanced by trapping the light between mirrors that form a cavity. Such a system makes it possible to observe the exchange of energy or information between the atoms/qubits and the light at a much higher rate than in free space. In this particular project, this scenario is realized with microwave frequency photons or phonons trapped on the surface of an electronic chip, with static qubits fabricated in place inside the on-chip cavities. This architecture for cavity QED, and for quantum computing, is thought to be highly promising since scaling it up to larger numbers of qubits may be achieved using conventional processor fabrication techniques that exist today.