Interview for Faculty Position

Opening the quantum tool box: from artificial atoms to photonic quantum phase transitions

Jens Koch

Yale University

In the early days of quantum mechanics, Gedanken experiments played a crucial role in probing the consistency of the quantum theoretical framework. The “Gedanken” (thought) character was mainly owed to the fact that the proposed experiments seemed outrageously difficult - if not impossible - to carry out. Much, however, has changed since then. Modern experiments have succeeded in eliminating this Gedanken character and have opened new vistas for harnessing quantum mechanics in applications such as quantum computing and quantum simulation. One approach to taming the quantum world consists of constructing tunable artificial atoms and devising schemes for manipulating and measuring their quantum states at will.

In this talk, I will introduce you to two artificial atoms named “transmon” and “fluxonium”, which we developed at Yale and which currently stand in the forefront of coherence in superconducting circuits. After outlining how the quantum state of such circuits can be controlled and probed with microwave photons, I will discuss the exciting idea of coupling resonator arrays to these artificial atoms. Such Jaynes-Cummings lattices allow one to explore strong correlations and quantum phase transitions in a system of interacting photons. Once realized, such a system could be employed as a quantum simulator of interesting many-body states.