Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

28 GHz Wireless Channel Characterization for a Quantum Computer Cryostat at 4 Kelvin

Ama Bandara, Viviana Centritto Arrojo, Heqi Deng, Masoud Babaie, Fabio Sebastiano, Edoardo Charbon, Evgenii Vinogradov, Eduard Alarcon, Sergi Abadal

TL;DR

The paper tackles wiring and thermal-load constraints in scalable quantum computers by evaluating wireless intra-cryostat links using a 28 GHz on-chip differential dipole antenna designed for 4 K operation, modeled within a realistic cryostat in CST. It demonstrates strong impedance matching near 28 GHz (S11 ≈ -21 dB) and characterizes the channel via channel impulse responses across multiple receiver positions, revealing high SNRs but notable multipath-induced delay dispersion. The RMS delay spread ranges from 0.3 to 0.7 ns, with coherence bandwidth on the order of a few GHz, indicating usable short-range wireless links within a cryostat. The results support the feasibility of modular, wireless interconnects for quantum architectures while highlighting considerations for qubit interference and future antenna-design optimizations to enhance reliability and scalability.

Abstract

The scalability of quantum computing systems is constrained by the wiring complexity and thermal load introduced by dense wiring for control, readout and synchronization at cryogenic temperatures. To address this challenge, we explore the feasibility of wireless communication within a cryostat for a multi-core quantum computer, focusing on wireless channel characterization at cryogenic temperatures. We propose to place on-chip differential dipole antennas within the cryostat, designed to operate at 28 GHz in temperatures as low as 4 K. We model the antennas inside a realistic cryostat and, using full-wave electromagnetic simulations, we analyze impedance matching, spatial field distribution, and energy reverberation due to metallic structures. The wireless channel is characterized through measured channel impulse response (CIR) across multiple receiver antenna positions. The results demonstrate potential for reliable shortrange communication with high Signal-to-Noise Ratio (SNR) and limited sensitivity to positional variation, at the cost of nonnegligible delay spread, due to significant multipath effects.

28 GHz Wireless Channel Characterization for a Quantum Computer Cryostat at 4 Kelvin

TL;DR

The paper tackles wiring and thermal-load constraints in scalable quantum computers by evaluating wireless intra-cryostat links using a 28 GHz on-chip differential dipole antenna designed for 4 K operation, modeled within a realistic cryostat in CST. It demonstrates strong impedance matching near 28 GHz (S11 ≈ -21 dB) and characterizes the channel via channel impulse responses across multiple receiver positions, revealing high SNRs but notable multipath-induced delay dispersion. The RMS delay spread ranges from 0.3 to 0.7 ns, with coherence bandwidth on the order of a few GHz, indicating usable short-range wireless links within a cryostat. The results support the feasibility of modular, wireless interconnects for quantum architectures while highlighting considerations for qubit interference and future antenna-design optimizations to enhance reliability and scalability.

Abstract

The scalability of quantum computing systems is constrained by the wiring complexity and thermal load introduced by dense wiring for control, readout and synchronization at cryogenic temperatures. To address this challenge, we explore the feasibility of wireless communication within a cryostat for a multi-core quantum computer, focusing on wireless channel characterization at cryogenic temperatures. We propose to place on-chip differential dipole antennas within the cryostat, designed to operate at 28 GHz in temperatures as low as 4 K. We model the antennas inside a realistic cryostat and, using full-wave electromagnetic simulations, we analyze impedance matching, spatial field distribution, and energy reverberation due to metallic structures. The wireless channel is characterized through measured channel impulse response (CIR) across multiple receiver antenna positions. The results demonstrate potential for reliable shortrange communication with high Signal-to-Noise Ratio (SNR) and limited sensitivity to positional variation, at the cost of nonnegligible delay spread, due to significant multipath effects.
Paper Structure (11 sections, 3 equations, 4 figures)

This paper contains 11 sections, 3 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Methodology
  3. Cryo-CMOS Antenna Model
  4. Cryostat Model
  5. Performance Metrics
  6. Signal to Noise Ratio
  7. Delay Spread
  8. Performance Evaluation
  9. On-Chip Antenna Inside the Cryostat
  10. Wireless Channel
  11. Conclusion

Figures (4)

  • Figure 1: Integrated on-chip differential dipole antennas inside the cryostat, which are positioned above the QPUs. The cryo-transceivers are connected to the QPUs through wires, while the wireless plane is fulfilling the need for classical interconnects (control/synchronization) in a modular architecture.
  • Figure 2: Simulation setup implemented in CST MWS. (a) Cross-section of the simulation model of the cryostat, together with a detailed map of the evaluated antenna positions within the boundaries of 4 K temperature level. (b) Top-view and cross-section of the differential-fed dipole antenna design, including details on the thickness of the top metal, insulator and substrate layer. (c) Reflection coefficient (dB) of the on-chip differential dipole within the cryostat, showing operation at 28 GHz.
  • Figure 3: Spatial distribution of the electrical field across the cryostat as observed in the cross-section, general top view, and top view at the plane of the antennas.
  • Figure 4: Characterization of the wireless channel in a 4-K cryostat environment at 28 GHz. (a) Measured power delay profile of the wireless links $A-B_{1}, A-B_{3}, A-B_{6}$ with $P_{TX}=0$ dB (b) Return loss of transmitter $A$ and $S_{21}$ of the different antenna for $B_{1}, B_{3}, B_{6}.$ (c) Delay spread over distance for the wireless links $A-B_{1-6}$ with differential feeds. (d) Received power at intended antenna positions of $B_{1-6}$ from a single transmission. (e) SNR as a function of bandwidth assuming $P_{TX}= -30$ dBm.