Scalable signal mixer stages in quantum processors

Abstract

The development of cost-effective and compact quantum computers in the Quantum Technology Laboratory (QTL) at Chalmers University of Technology demands that the hardware of the control system can easily be scaled with the number of qubits. In this thesis the design and development of a rack instrument prototype is presented along with an evaluation of its performance. Three printed circuit boards were constructed and mounted in a subrack with the purpose of upconverting and downconverting the frequency of signals to and from the quantum processor with IQ mixers. Measurements performed at QTL confirmed image rejection and local oscillator signal suppression between 49-51 dB and 86-85 dB respectively for the calibrated mixers. The instrument was not found to add any measurable phase noise beyond what was already present in the signal source. Possible future improvements include integrating amplifiers to both up- and downconverting mixer stages. Including amplifiers will also allow for an additional local oscillator signal distribution card to be added, which would improve the phase stability in the quantum computing system.