Abstract
We analyze charge fluctuations in a parasitic state strongly coupled to a superconducting Josephson-junction-based charge detector. The charge dynamics of the state resembles that of electron transport in a quantum dot with two charge states, and hence we refer to it as a two-level fluctuator. By constructing the distribution of waiting times from the measured detector signal and comparing it with a waiting time theory, we extract the electron in- and out-tunneling rates for the two-level fluctuator, which are severely asymmetric.
Highlights
Parasitic states including charge traps are present in almost all solid-state devices and there have been several proposals on how to avoid them [1,2,3,4,5,6,7,8,9]
We employ a superconducting charge detector which consists of two Al/Al2O3/Al Josephson junctions in series with resistances and capacitances Ri, Ci, i = 1, 2 and a superconducting gap, which form a charge island with a charging energy of Ech = e2/C, where C = C1 + C2 + Cc + Cg, e is the elementary charge, Cg is the capacitive coupling between the gate and the island, and Cc is the mutual capacitance between the Two-level fluctuators (TLFs) and the detector island
The detector signal is filtered with a twopoint moving averaging window, which results in a detector bandwidth of D/(2π ) = 11.25 Hz
Summary
Parasitic states including charge traps are present in almost all solid-state devices and there have been several proposals on how to avoid them [1,2,3,4,5,6,7,8,9]. Electron waiting times have been investigated for a wide range of physical systems including quantum dots [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36], coherent conductors [37,38], molecular junctions [39,40], and superconducting systems [41,42,43,44,45,46,47]. Waiting time distributions capture the interference effects in double-dot setups [21], reveal the correlations in multichannel systems [25,48], allow us to separate slow and fast dynamics in Cooper-pair splitters [46], resolve few-photon processes [49], and even investigate the topological superconductivity in hybrid junctions [45,47].
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