Superconducting qubit readout using a multi-stage quantum amplifier readout chain

The current available superconducting quantum processors (IBM, Google,…), operated at temperatures down to 20 mK (-273,13 °C), have a limited amount of quantum bits (qubits) because of the difficulty to have compact readout chains allowing to measure several qubits simultaneously. The current cryogenic amplifiers used for superconducting qubit readout are based on semiconductor technologies, which limits their performances because of their electrical resistance. Moreover, they are powered with DC-current and have to be operated at elevated temperature (4 K) to dissipate the heat they produce.

The topic of this PhD is to design a new kind of cryogenic amplifiers, called parametric amplifiers, based on superconducting materials in order to replace semiconductor-based ones. The designed amplifier will be fabricated in the industrial-grade cleanroom of CEA-Leti, and further used to measure our superconducting qubits.