AQP Seminar: Experimental benchmark of small quantum processors
Aalto Quantum Physics -seminaari (Nanotalo). Puhuja: Mr. Johannes Heinsoo (QCD group, Aalto-yliopisto)
The number of superconducting qubits tends to double during the study of a single PhD student, and companies including Google , IBM , Intel  and Rigetti  already claim to work on quantum processors sufficiently large to demonstrate quantum supremacy. These machines employ transmon type qubits with improved coherence and reliable gate performance. I will give a short introduction to the transmon qubits and experiments carried out to benchmark the performance of 2, 4 and 8 qubit devices in ETH Zürich. The benchmark experiments include a free-will-based Bell test , a full state tomography of 4-qubit maximally-entangled GHZ state, entanglement swapping, entanglement distillation and characterization of 8-qubit low-crosstalk frequency-multiplexed readout circuit . The results of these benchmark experiments allow for the identification of specific challenges in designing and running multi-qubit experiment and, thus, provide essential information for building larger quantum devices in the near future.
 Challenging local realism with human choices, The BIG Bell Test Collaboration, Nature 557, 212–216 (2018), also in arXiv:1805.04431
 Rapid High-fidelity Multiplexed Readout of Superconducting Qubits, J. Heinsoo et al., Phys. Rev. Applied 10, 034040 (2018), also in arXiv:1801.07904