Cavity Quantum Electrodynamics and Quantum Information Processing with Superconducting Circuits

Programme: Swiss National Science Foundation (SNSF)
Theme: Mathematics, Natural and Engineering Sciences - Independent Basic Research

Project Participants: Quantum Device Lab, ETH Zürich

Official project summary

Today individuals, businesses, industries, and societies as a whole have a quickly growing need for processing and storing ever increasing amounts of information. Intense publicly and privately funded research in information technologies has so far been able to fulfill these needs by miniaturization and large scale integration of electronic components used for data storage and processing. In the not so distant future the miniaturization will approach atomic scales. At this point, quantum mechanical effects will start to dominate over classical ones and seriously alter or impede the way electronic components will function. In the past 10 to 15 years, however, a solid theoretical framework has been developed that suggests to make use of quantum effects in a novel approach for information processing called quantum computation. A number of fundamental concepts of quantum information processing have been experimentally demonstrated already in a variety of physical realizations such as nuclear magnetic moments, ions, charges, spins and flux quanta. However, a larger scale physical realization of a quantum computer based on solid state approaches remains an extremely challenging goal. The question if and how a large scale quantum computer can be realized with state of the art technology is still an open one. But if realized it would provide an unprecedented increase in processing efficiency in comparison to present day computing technologies.

To search for a scalable solid-state realization of a quantum information processor while simultaneously pushing forward the limits of integrated circuit technology is our long term goal within the context of quantum information science. In the framework of this project we investigate the use of superconducting circuits operated at low temperatures and microwave frequencies for achieving this ambitious goal. In particular, we will explore a specific approach to this problem which exploits the strong controllable interaction between two-level quantum electronic circuits used as qubits, the carriers of quantum information, with single photons stored in high quality on-chip cavities to develop a promising quantum computing architecture. We have already demonstrated the principle feasibility of this approach in our labs. ETH Zurich with its excellent micro- and nano-fabrication facilities, a tradition for low temperature physics and existing complementary activities in both experimental and theoretical quantum information science has proven to be an ideal setting to start research in this new field as demonstrated by the success of the ongoing project.

This project will focus on our novel approach - now known as circuit quantum electrodynamics - to investigate coherent matter-light interaction and its use for quantum information processing in a solid-state setting. Based on the previous successes on the single qubit and single photon level we will now explore new regimes in multi-qubit and multi-photon interactions in quantum systems with a number of fully controllable degrees of freedom. This fundamental research in the domain of quantum optics will be at the foundations of further exploring the potential of the circuit QED approach for quantum information processing by demonstrating a quantum algorithm. To approach this goal, we will explore the effect of materials and fabrication processes on coherence properties of superconducting circuits and develop techniques to control and read-out superconducting qubits with high fidelity.

With its conclusion this project will have explored the interaction of a controlled number of photons with a controlled number of atoms on a fundamental level. Our approach combines ideas from mesoscopic condensed matter physics, atomic physics and quantum optics to explore new regimes of matter/light interaction difficult to conceive in any other setting. We will have demonstrated the potential of our solid-state based circuit QED approach for quantum information processing by realizing a quantum algorithm. The project will also contribute to establish a leading research team in Switzerland while fostering international collaborations and educating and promoting students and young scientist at all levels. The results of the project will have an impact on quantum information science in general but are also relevant for applications such as microwave single photon sources, detectors and solid-state instrumentation.