Quantum computers require interfaces with classical electronics for efficient qubit control, measurement and fast data processing. Fabricating the qubit and the classical control layer using the same technology is appealing because it will facilitate the integration process, improving feedback speeds and offer potential solutions to wiring and layout challenges. Integrating classical and quantum devices monolithically, using complementary metal-oxide-transistor (CMOS) processes, enables the processor to profit from the most mature industrial technology for the fabrication of large scale circuits. Here we demonstrate the integration of a single-electron charge storage CMOS quantum dot with a CMOS transistor for control of the readout via gate-based dispersive sensing using a lumped element
LC resonator. The control field-effect transistor (FET) and quantum dot are fabricated on the same chip using fully-depleted silicon-on-insulator technology. We obtain a charge sensitivity of
δq=165μeHz−1/2 when the quantum dot readout is enabled by the control FET. Additionally, we observe a single-electron retention time of the order of a second when storing a single-electron charge on the quantum dot at milli-Kelvin temperatures. These results demonstrate first steps towards time-based multiplexing of gate-based dispersive qubit readout in CMOS technology opening the path for the development of an all-silicon quantum-classical processor.
We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (SSET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the SSET are observed at a temperature of 0.3 K. Coupling of the SSET to the QD is confirmed by using the SSET to perform sensing of the QD charge state.
The characteristics of the single Cooper pair transistor, a key component of single-charge electronics that manipulates single or Cooper pair electrons via the Coulomb blockade phenomenon, are discussed in this article. Due to these characteristics, the single Cooper pair transistor plays an important role in metrology such as sensitive electrometry and quantum computing. Electron beam lithography and electron gun evaporation are used to fabricate the single Cooper pair transistor. The measurement is performed at lower temperatures than 100 mK by using a dilution refrigerator. It has been found that only the tunneling of Cooper pairs of electrons is shown by the relationship between the gate voltage and the supercurrent. It indicates that a single Cooper pair transistor can be used as a sensitive sensor when integrated into other devices, exhibiting the tunneling properties of Cooper pairs at 16 GHz.