Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Focussed Session: Superconducting Quantum Circuits

TT 13.1: Invited Talk

Tuesday, March 24, 2009, 09:30–10:00, HSZ 03

Photons, Qubits and Computers - A Quantum Mechanics Lab on a Chip — •Andreas Wallraff — Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland

In our lab we experimentally investigate the interaction of matter and light on the level of single quanta. Our approach, known as circuit quantum electrodynamics [1], combines ideas of atomic physics, quantum optics and solid state physics to perform state of the art quantum mechanics experiments on a single chip. This is achieved by coupling single photons stored in high quality microwave frequency resonators to fully controllable superconducting two-level systems (qubits) realized in macroscopic electronic circuits. In particular, we have recently observed the formation of qubit/light molecules involving one, two or three photons [2], where we probe the quantum nonlinearity of the qubit/field interaction. This experiment unambiguously demonstrates that the radiation field in the on-chip cavity is quantized. We have also performed quantum optics experiments with no photons at all. In this situation, i.e. in pure vacuum, we have been able to resolve the non-resonant interaction of a qubit with the cavity vacuum fluctuations [3]. This interaction leads to a renormalization in the qubit transition frequency, known as the Lamb shift. The high degree of control achievable over a collection of two-level systems and their interactions also renders the circuit QED architecture attractive for quantum information processing.

[1] A. Wallraff et al., Nature (London) 431, 162 (2004).

[2] J. Fink et al., Nature (London) 454, 315 (2008).

[3] A. Fragner et al., Science 322, 1357 (2008).