Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 4: Superconductivity: Qubits I

TT 4.8: Vortrag

Montag, 12. März 2018, 11:30–11:45, H 2053

Qubit readout using a transmon with a V-shaped energy diagram — Remy Dassonneville, Luca Planat, Javier Puertas, Farshad Foroughi, Cecile Naud, Wiebke Guichard, Nicolas Roch, and •Olivier Buisson — University Grenoble Alpes & CNRS, Institut Néel, F-38000 Grenoble, France.

The most widely used scheme to perform qubit readout in cQED relies on the dispersive coupling between a qubit and a harmonic oscillator. However, despite important progresses, implementing a fast and high fidelity readout remains nowadays a major challenge. Indeed, inferring a qubit state is limited by the trade-off between speed and accuracy due to Purcell effect and transitions induced by readout photons in the resonator. To overcome this, we introduce a new device: a transmon with a V-shaped energy diagram, embedded in 3D architecture. It is made of two transmons coupled via a large inductance[1]. The resulting circuit presents two qubits longitudinally coupled called qubit and ancilla. Using symmetry rules[2], the ancilla can be strongly coupled to the cavity while the qubit remains uncoupled. However due to their strong longitudinal coupling, the qubit state can still be inferred through the ancilla state. A theoretical study[3] has predicted a QND readout with fidelity as high as 99.9
É. Dumur, et al, Phys. Rev. B 92, 020515(R) (2015).
É. Dumur, et al, IEEE Trans. Appl. Supercond. 26, 1700304 (2016).
I.Diniz, et al, , Phys. Rev. A 87, 033837 (2013).