Jonas Bühler - DR project
Scalable integrated readout circuits for silicon quantum dots at cryogenic temperatures
Quantum computing is one of the promising candidates to overcome the limitations of "classical" computing, e.g. von Neumann architecture. Nowadays much progress has been made on the implementation of scalable qubits. This work focuses on semiconductor qubits, which need operating temperatures near 0 K. Room temperature electronics for control and readout, which are limiting the bandwidth and the scalability due to parasitic elements and heat conduction, are still widely used. Some progress has been made to integrate the qubit control and readout in the direct vicinity of the qubit at cryogenic temperatures. Especially readout electronics still have a limited scalability because of circuit size and power consumption. This work investigates solutions to overcome those limitations by comparing different readout architectures and implement a multiplexed and integrated readout circuit with low area and power consumption. To achieve this goal, we focus on detecting single charge movements inside a quantum dot with a capacitively coupled charge sensor. The developed integrated circuit (Figure 1) reads the conductance of the charge sensor and gives a digital value depending on the existence of a charge transition. This is sufficient to measure the result of a computation performed by a quantum computer. For tuning the quantum bits we use the one-bit value to generate the first derivative of a charge stability diagram by averaging over multiple sweeps.
The integrated circuit produced in a 22nm FD-SOI technology will be placed on top of scalable quantum computing architectures at cryogenic temperatures. This helps to reduce the amount of wires to room temperature and hence reduce the heat conduction from room temperature to cryogenic electronics. Therefore, it might be a crucial step on the way to a multi-million qubit quantum computer.