Scaling Superconducting Quantum Computers with Chiplet Architectures

  1. Kaitlin N. Smith,
  2. Gokul Subramanian Ravi,
  3. Jonathan M. Baker,
  4. and Frederic T. Chong
Fixed-frequency transmon quantum computers (QCs) have advanced in coherence times, addressability, and gate fidelities. Unfortunately, these devices are restricted by the number of
on-chip qubits, capping processing power and slowing progress toward fault-tolerance. Although emerging transmon devices feature over 100 qubits, building QCs large enough for meaningful demonstrations of quantum advantage requires overcoming many design challenges. For example, today’s transmon qubits suffer from significant variation due to limited precision in fabrication. As a result, barring significant improvements in current fabrication techniques, scaling QCs by building ever larger individual chips with more qubits is hampered by device variation. Severe device variation that degrades QC performance is referred to as a defect. Here, we focus on a specific defect known as a frequency collision. When transmon frequencies collide, their difference falls within a range that limits two-qubit gate fidelity. Frequency collisions occur with greater probability on larger QCs, causing collision-free yields to decline as the number of on-chip qubits increases. As a solution, we propose exploiting the higher yields associated with smaller QCs by integrating quantum chiplets within quantum multi-chip modules (MCMs). Yield, gate performance, and application-based analysis show the feasibility of QC scaling through modularity.

Short-Range Microwave Networks to Scale Superconducting Quantum Computation

  1. Nicholas LaRacuente,
  2. Kaitlin N. Smith,
  3. Poolad Imany,
  4. Kevin L. Silverman,
  5. and Frederic T. Chong
A core challenge for superconducting quantum computers is to scale up the number of qubits in each processor without increasing noise or cross-talk. Distributing a quantum computer
across nearby small qubit arrays, known as chiplets, could solve many problems associated with size. We propose a chiplet architecture over microwave links with potential to exceed monolithic performance on near-term hardware. We model and evaluate the chiplet architecture in a way that bridges the physical and network layers. We find concrete evidence that distributed quantum computing may accelerate the path toward useful and ultimately scalable quantum computers. In the long-term, short-range networks may underlie quantum computers just as local area networks underlie classical datacenters and supercomputers today.