Abhinandan Antony

Meter-scale quantum interconnects between large quantum processors

  1. Neereja M. Sundaresan,
  2. Nicholas Cotaj,
  3. Yadav Prasad Kandel,
  4. Eric Lewandowski,
  5. Christian Robert Longton,
  6. Yves Martin,
  7. Jae-woong Nah,
  8. Kathryn Pooley,
  9. Martin Sandberg,
  10. Michael Scanlon,
  11. Chi Xiong,
  12. Emanuil Sashev Yanev,
  13. David Abraham,
  14. Abhinandan Antony,
  15. Vincent Arena,
  16. Nicholas Bornman,
  17. Khanh Dang,
  18. Oliver Dial,
  19. Christopher Guarino,
  20. Gabriel Haspil,
  21. Jared Hertzberg,
  22. Kentaro Heya,
  23. Swetha Kamlapurkar,
  24. Michael Karschner,
  25. George Keefe,
  26. Eric Liniger,
  27. Laura Luo,
  28. Thomas G. McConkey,
  29. David Olson,
  30. Jason Orcutt,
  31. Dmitry Ovchinnikov,
  32. Timothy Phung,
  33. Sankeerth Rajalingam,
  34. Michael Selvanayagam,
  35. William Shanks,
  36. Dongbing Shao,
  37. Abigail Shearrow,
  38. Adam Stabile,
  39. Jiri Stehlik,
  40. Joseph Suttle,
  41. Jeng-Bang Yau,
  42. and Eric Zhang
Modular quantum architecture requires long-distance quantum interconnects to stitch together individual processor modules. Such interconnects, long-distance couplers or L-couplers,
must support coherent quantum operation over meter-scale distances and scale to multiple connections between any two modules. Here we demonstrate four L-couplers operating between two 120-qubit IBM Nighthawk R1 superconducting qubit processors. Each L-coupler joins two Nighthawk lattice qubits through two frequency-tunable L-qubits, two RF-SQUID based „i2m“ couplers, and 80 cm of superconducting aluminum coax. Each cable installs perpendicular to the processor surface, to enable denser connections, and is joined to the chip by an indium-to-indium room temperature pressure bond made after both modules were mounted. L-coupler modes near 5 GHz, with internal quality factors of 0.86 to 1.09e6, carry relay-based state transfer at a mean network benchmarking fidelity of 99.00%, with a best link of 99.29 +/- 0.07%. We then realize distant CZ gates between lattice qubits in separate modules at a mean fidelity of 94.75%, with a best link of 96.42 +/- 0.28%, and use them to generate entangled states across the two processors, including a demonstration of simultaneous Bell pair generation using two adjacent L-couplers. These four high-fidelity L-couplers establish a practical path to scalable quantum interconnects for modular quantum computing.
arxiv pdf

Miniaturizing transmon qubits using van der Waals materials

  1. Abhinandan Antony,
  2. Martin V. Gustafsson,
  3. Guilhem J. Ribeill,
  4. Matthew Ware,
  5. Anjaly Rajendran,
  6. Luke C.G. Govia,
  7. Thomas A. Ohki,
  8. Takashi Taniguchi,
  9. Kenji Watanabe,
  10. James Hone,
  11. and Kin Chung Fong
Quantum computers can potentially achieve an exponential speedup versus classical computers on certain computational tasks, as was recently demonstrated in systems of superconductingqubits. However, these qubits have large footprints due to the need of ultra low-loss capacitors. The large electric field volume of \textit{quantum compatible} capacitors stems from their distributed nature. This hinders scaling by increasing parasitic coupling in circuit designs, degrading individual qubit addressability, and limiting the minimum achievable circuit area. Here, we report the use of van der Waals (vdW) materials to reduce the qubit area by a factor of >1000. These qubit structures combine parallel-plate capacitors comprising crystalline layers of superconducting niobium diselenide (NbSe2) and insulating hexagonal-boron nitride (hBN) with conventional aluminum-based Josephson junctions. We measure a vdW transmon T1 relaxation time of 1.06 μs, demonstrating that a highly-compact capacitor can reach a loss-tangent of <2.83×10−5. Our results demonstrate a promising path towards breaking the paradigm of requiring large geometric capacitors for long quantum coherence in superconducting qubits, and illustrate the broad utility of layered heterostructures in low-loss, high-coherence quantum devices.[/expand]
arxiv pdf