Magnetic-Field-Compatible Superconducting Transmon Qubit

Abstract

We present a hybrid semiconductor-based superconducting qubit device that remains coherent at magnetic fields up to 1 T. The qubit transition frequency exhibits periodic oscillations with the magnetic field, consistent with interference effects due to the magnetic flux threading the cross section of the proximitized semiconductor nanowire junction. As the induced superconductivity revives, additional coherent modes emerge at high magnetic fields, which we attribute to the interaction of the qubit and low-energy Andreev states.

Quasiparticle trapping by orbital effect in a hybrid superconducting-semiconducting circuit

“…This observation is in agreement with the density of states being confined towards the superconducting shell, improving the induced superconducting gap. We observe a local minimum around B = 0.3 T, consistent with the flux induced interference effects as explained in the main text, and also reported by [26,30].…”

“…When the JJ is protected by the gate-controlled QP filters, we find peaks of enhanced charge-parity lifetimes induced by the magnetic field and centered around odd multiples of B ∼ 280 mT. We attribute these enhancements to the formation of quasiparticle traps in the ungated NW segments as a result of a local suppression of the induced gap by the orbital effect [26][27][28][29][30], efficiently trapping QPs away from the JJ. Finally we conclude that such devices can be operated at high magnetic field without being limited by QPP, paving the way for implementing proposals for novel superconducting-topological hybrid qubits [31,32].…”

“…We attribute these to the orbital effect of the magnetic field, that occurs when the cylindrical electron density in the leads is threaded by magnetic flux, leading to the suppression of the proximity-induced gap [Fig. 4(d)] [26,27,30]. Such a cylindrical electron density profile is a manifestation of charge accumulation at the InAs NW surface for V g ≥ 0 [29].…”

“…To date, magnetic field studies of QP dynamics in Josephson junction (JJ) circuits consist only of time-averaged experiments performed be-low B < 0.3 T. These works demonstrated the increase in QPP due to field induced Cooper pair breaking [6,20]. Recent developments in magnetic field compatible superconducting resonators [21] and advances in semiconducting NW-based JJs enabled novel semiconductor-based superconducting circuits [22][23][24], that operate in magnetic fields up to 1 T [25,26]. Such devices enable the investigation of QPP in the unexplored magnetic field parameter space that is essential in topological quantum computing, where a magnetic field as strong as 1 T may be required [19].…”

Growth of PbTe nanowires by molecular beam epitaxy

“…By defining quantum dots, e.g. using gate potentials, spin qubits can be studied, while in NW Josephson junctions gate-tunable transmon qubits were realized [6]. A substantial fraction of the research in the field of NW quantum computation is focused on III-V semiconductors, such as InSb and InAs [2][3][4][5].…”