Cross-Platform Verification with Modular Superconducting Devices

Future large-scale quantum computers will necessarily be modular. Thus, benchmarking strategies are required to efficiently verify the operation of different modules. This can be achieved by the pairwise comparison of different modules, known as cross-platform verification. For superconducting quantum devices, modularity can be obtained over multiple scales: within a sample package, between sample packages in the same cryostat, and between cryostats. We demonstrate single package-scale modularity using flip-chip bonding, whereby multiple top chips are bonded onto the same carrier chip. We present a six-qubit flip-chip modular device consisting of two three-qubit modules. We use this device to implement cross-platform verification protocols to estimate state preparation fidelity between the two modules. We discuss the exponential scaling, with qubit number, of protocols utilizing only classical communication between the modules, and use an inter-module two-qubit gate to achieve sub-exponential scaling in the verification protocol [1].



[1] Knörzer, J. et al., Phys. Rev. A 107, 062424 (2023)