S. Liu

FPGA-based electronic system for the control and readout of superconducting qubit systems

  1. Y. Yang,
  2. Z. Shen,
  3. X. Zhu,
  4. Z. Wang,
  5. G. Zhang,
  6. J. Zhou,
  7. C. Deng,
  8. S. Liu,
  9. and Q. An
This paper reports the development of an electronic system for the control and readout of superconducting qubits. The system includes a timing control module (TCM), four-channel arbitrary
waveform generators (AWGs), four-channel data acquisition modules (DAQs), six-channel bias voltage generators (BVGs), a controller card, and mixers. The AWGs have a 2-GSa/s sampling rate and a 14-bit amplitude resolution. The DAQs provide a 1-GSa/s sampling rate and 12-bit amplitude resolution. The BVGs provide an ultra-precise DC voltage with a noise level of ~6 {\mu}Vp-p. The TCM sends system clock and global triggers to each module through a high-speed backplane to achieve precise timing control. These modules are implemented in a field-programmable gate array (FPGA). While achieving highly customized functions, the physical interface and communication protocol are compatible with each other. The modular design is suitable for quantum computing experiments of different scales up to hundreds of qubits. We implement a real-time digital signal processing system in the FPGA, enabling precise timing control, arbitrary waveform generation, parallel IQ demodulation for qubit state discrimination, and the generation of real-time qubit-state-dependent trigger signals for active feedback control. We demonstrate the functionalities and performance of this system using a fluxonium quantum processor.
arxiv pdf

A flux tunable superconducting quantum circuit based on Weyl semimetal MoTe2

  1. K. L. Chiu,
  2. D. G. Qian,
  3. J. W. Qiu,
  4. W. Y. Liu,
  5. D. Tan,
  6. V. Mosallanejad,
  7. S. Liu,
  8. Z. T. Zhang,
  9. Y. Zhao,
  10. and D. P. Yu
Weyl semimetals for their exotic topological properties have drawn considerable attention in many research fields. When in combination with s-wave superconductors, the supercurrent
can be carried by their topological surface channels, forming junctions mimic the behavior of Majorana bound states. Here, we present a transmon-like superconducting quantum intereference device (SQUID) consists of lateral junctions made of Weyl semimetal Td-MoTe2 and superconducting leads niobium nitride (NbN). The SQUID is coupled to a readout cavity made of molybdenum rhenium (MoRe), whose response at high power reveal the existence of the constituting Josephson junctions (JJs). The loop geometry of the circuit allows the resonant frequency of the readout cavity to be tuned by the magnetic flux. We demonstrate a JJ made of MoTe2 and a flux-tunable transmon-like circuit based on Weyl materials. Our study provides a platform to utilize topological materials in SQUID-based quantum circuits for potential applications in quantum information processing.
arxiv pdf