Kvanttitietokone: Technical developments and single-shot qubit readout

Aalto Quantum Physics Seminar (Nanotalo). Speaker: Dr. Jan Goetz (QCD group, Aalto University).

We summarize technical developments within the Kvanttitietokone (quantum computer) project. We will present ongoing work for material development and fabrication techniques used to establish three-dimensional microwave structures. In addition, we will present our approach to establish a scalable control architecture suitable for randomized benchmarking and feedback experiments. These techniques rely on single-shot readout of superconducting quantum bits (qubits). We will present first results of single-shot measurements with a process fidelity of approximately 90%, which is limited by qubit relaxation. We will discuss the optimization procedure for our travelling wave parametric amplifier and the algorithms for making single-shot decisions. Our results point towards future implementations of fast feedback, quantum control, and quantum tomography. 
We acknowledge financial support by Janne and Aatos Erkko foundation, European Research Council under Grant No. 681311 (QUESS); by Academy of Finland under Grants No. No. 265675, No. 276528, No. 284621, No. 305237, No. 305306, No. 308161, and No. 312300. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 795159.