Shobhan Kulshreshtha

Full control of superconducting qubits with combined on-chip microwave and flux lines

  1. Riccardo Manenti,
  2. Eyob A. Sete,
  3. Angela Q. Chen,
  4. Shobhan Kulshreshtha,
  5. Jen-Hao Yeh,
  6. Feyza Oruc,
  7. Andrew Bestwick,
  8. Mark Field,
  9. Keith Jackson,
  10. and Stefano Poletto
As the field of quantum computing progresses to larger-scale devices, multiplexing will be crucial to scale quantum processors. While multiplexed readout is common practice for superconducting
devices, relatively little work has been reported about the combination of flux and microwave control lines. Here, we present a method to integrate a microwave line and a flux line into a single „XYZ line“. This combined control line allows us to perform fast single-qubit gates as well as to deliver flux signals to the qubits. The measured relaxation times of the qubits are comparable to state-of-art devices employing separate control lines. We benchmark the fidelity of single-qubit gates with randomized benchmarking, achieving a fidelity above 99.5%, and we demonstrate that XYZ lines can in principle be used to run parametric entangling gates.
arxiv pdf

Floating tunable coupler for scalable quantum computing architectures

  1. Eyob A. Sete,
  2. Angela Q. Chen,
  3. Riccardo Manenti,
  4. Shobhan Kulshreshtha,
  5. and Stefano Poletto
We propose a floating tunable coupler that does not rely on direct qubit-qubit coupling capacitances to achieve the zero-coupling condition. We show that the polarity of the qubit-coupler
couplings can be engineered to offset the otherwise constant qubit-qubit coupling and attain the zero-coupling condition when the coupler frequency is above or below the qubit frequencies. We experimentally demonstrate these two operating regimes of the tunable coupler by implementing symmetric and asymmetric configurations of the coupler’s superconducting pads with respect to the qubits. Such a floating tunable coupler provides flexibility in designing large-scale quantum processors while reducing the always-on residual couplings.
arxiv pdf