ETH Polymer Physics seminar


2013-04-10
10:15 at HCI J 574

A superconducting artificial atom with two internal degrees of freedom

Olivier Buisson

Institut Néel, CNRS Grenoble, France

The richness of the energy level structure and the diversity of the associated transitions are at the heart of atomic and quantum optics experiments. They are provided by the multiples degrees of freedom existing in these systems. In our recent work, by adding a large inductance in a dc-SQUID phase qubit loop, we create a superconducting artificial atom with two internal degrees of freedom. This device can be described by two anharmonic oscillators labelled "s" (symmetric) and "a" (anti-symmetric) because the current oscillations at each junction can be either in-phase or in phase-opposition, respectively [1]. Spectroscopic measurements show an anti-crossing of two levels which demonstrates a non-linear coupling between the two modes “s” and “a”. We also demonstrate a time resolved up and down frequency conversion in the microwave domain [2]. Finally such artificial atom with two degrees of freedom can provide substantial benefits with regard to non destructive qubit readout. We present a theoretical study of a quantum nondemolition (QND) readout scheme based on a diamond- shaped artificial atom coupled to a microwave resonator in a circuit quantum electrodynamics (CQED) architecture [3].

[1] Non-linear coupling between the two oscillation modes of a dc-SQUID, F. Lecocq, et al, Phys. Rev. Lett. 107, 197002 (2011).

[2] Coherent Frequency Conversion in a Superconducting Artificial Atom with Two Internal Degrees of Freedom, F. Lecocq, et al, Phys. Rev. Lett. 108, 107001 (2012).

[3] Ultrafast QND measurements based on diamond-shape artificial atom. I. Diniz, et al, Phys. Rev. A 87, 033837 (2013).


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