We report on the investigation of Al single electron structures equipped with miniature (8 µm long) on-chip Cr resistors of R > R k = h/e 2 ≈ 26 kΩ. From the measurement of the Coulomb blockade in single-junction structures we evaluated the self-capacitance of our resistors per unit length, c ≈ 62 aF/µm. We demonstrate that the cotunneling current in the transistor samples in the Coulomb blockade regime obeys the power law, I ∝ V 3+(R/R k ) , predicted by Odintsov, Bubanja and Schön for a transistor having pure ohmic-resistance leads. The concept of the three-junction single electron pump with on-chip resistors (R-pump) is developed. We demonstrate that the implementation of the Rpump with a relative accuracy of the electron transfer of 10 −8 is quite feasible with the technology available.

We report on the operation of a single electron trap comprising a chain of four Al/AlOx/Al tunnel junctions attached, at one side, to a memory island and, at the other side, to a miniature on-chip Cr resistor (R ≈ 50 kΩ) which served to suppress cotunneling. At appropriate voltage bias the bistable states of the trap, with the charges differing by the elementary charge e, were realized. At low temperature, spontaneous switching between these states was found to be infrequent. For instance, at T =70 mK the system was capable of holding an electron for more than 2 hours, this time being limited by the time of the measurement.

We investigated transitions in an Al charge-phase qubit of SQUID-configuration which was inductively coupled to an rf tank circuit that made it possible to read out the state by measuring the Josephson inductance of the qubit. Depending on the flux and charge bias and on the amplitude of the rf-oscillations, we probed either the ground state or a dynamic change of the qubit states which we attributed to stochastic single quasiparticle tunneling onto and off the qubit island, involving an exchange of energy with the qubit. Within the scope of this model, a selection rule for quasiparticle-induced transitions in the qubit is discussed.

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We present investigations of Josephson charge-phase qubits inductively coupled to a radio-frequency driven tank-circuit enabling the readout of the states by measuring the Josephson inductance of the qubit. The circuits including junctions with linear dimensions of 60 nm and 80 nm are fabricated from Nb trilayer and allowing the determination of relevant sample parameters at liquid helium temperature. The observed partial suppression of the circulating supercurrent at 4.2 K is explained in the framework of a quantum statistical model. We have probed the ground-state properties of qubit structures with different ratios of the Josephson coupling to Coulomb charging energy at 20 mK, demonstrating both the magnetic control of phase and the electrostatic control of charge on the qubit island.Comment: 8 pages, 8 figure