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TT: Fachverband Tiefe Temperaturen
TT 50: Superconducting Electronics: SQUIDs, Qubits, Circuit QED II
TT 50.13: Vortrag
Donnerstag, 20. März 2025, 18:15–18:30, H36
Engineering Cooper Pair Bunching Using an Anharmonic Environment — •Surangana Sengupta1, Björn Kubala1,2, Joachim Ankerhold1, and Ciprian Padurariu1 — 1ICQ and IQST,Ulm University,Germany — 2Institute of Quantum Technologies, German Aerospace Center (DLR), Ulm, Germany
The electromagnetic environment of superconducting circuits provides exciting opportunities to engineer the tunneling of Cooper pairs. The simplest example is a dc biased Josephson junction in series with a microwave cavity. There has been extensive work showing that when the dc bias is chosen to be resonant with a well-defined cavity mode, the transport of Cooper pairs has the same statistics in the long time limit as that of the photon emission from the cavity mode [1].
In my talk, I extend this study to the case when the cavity mode is anharmonic. I investigate the case when the voltage bias is detuned from the transition between Fock states 0 and 1. Due to the anharmonicity however, this voltage can be resonant with half the transition between Fock states 0 and 2. Therefore, the process of coherent two-Cooper pair tunneling accompanied by two-photon creation is favored compared to single Cooper pair tunneling and single photon creation. This results in bunched Cooper pair tunneling, with Fano factor approaching F=2, and in a squeezed cavity state. I will compare this effect to a similar and competing inelastic co-tunneling process arising from second-order rotating wave approximation.
[1] M. Hofheinz et al., Phys. Rev. Lett. 106, 217005 (2011).
Keywords: Superconducting; Microwaves; Tunneling; Cooper Pairs; Josephson Junctions