Superconducting qubits in a flip-chip architecture

Journal Article · Thu Jun 10 00:00:00 UTC 2021 · Applied Physics Letters

DOI: https://doi.org/10.1063/5.0050173 · OSTI ID:1819508

Conner, C. R.  ^[1]; Bienfait, A. ^[2]; Chang, H. -S.  ^[1]; Chou, M. -H.  ^[1]; Dumur, É. ^[3]; Grebel, J.  ^[1]; Peairs, G. A.  ^[4]; Povey, R. G.  ^[1]; Yan, H. ^[1]; Zhong, Y. P. ^[5]; Cleland, A. N.  ^[6]

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1. Univ. of Chicago, IL (United States)
2. Univ. of Chicago, IL (United States); Univ. of Lyon (France)
3. Univ. of Chicago, IL (United States); Univ. of Grenoble Alpes (France); Argonne National Lab. (ANL), Argonne, IL (United States)
4. Univ. of Chicago, IL (United States); Univ. of California, Santa Barbara, CA (United States)
5. Univ. of Chicago, IL (United States); Univ. of Science and Technology of China, Shenzhen (China)
6. Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)

Flip-chip architectures have recently enabled significant scaling-up of multi-qubit circuits and have been used to assemble hybrid quantum systems that combine different substrates, for example, for quantum acoustics experiments. The standard flip-chip method uses superconducting galvanic connections between two substrates, typically implemented using sophisticated indium wafer-bonding systems, which give highly reliable and temperature-cyclable assemblies, but are expensive, somewhat inflexible in design, and require robust substrates that can sustain the large compressive forces required to cold-weld the indium bonds. A much simpler method is to assemble dies using very low-force contacts and air-dried adhesives, although this does not provide a galvanic contact between the dies. In this work, we demonstrate that the latter technique can be used to reliably couple superconducting qubit circuits, in which the qubits are on separate dies, without the need for a galvanic connection. We demonstrate full vector qubit control of each qubit on each of the two dies, with high-fidelity single-shot readout, and further demonstrate entanglement-generating excitation swaps as well as benchmark a controlled-Z entangling gate between the two qubits on the two dies. This exemplifies a simple and inexpensive assembly method for two-plus-one-dimensional quantum circuit integration that supports the use of delicate or unusually shaped substrates.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); US Air Force Office of Scientific Research (AFOSR); US Army Research Laboratory (USARL); USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Basic Energy Sciences (BES); University of Chicago
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1819508
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 23 Vol. 118; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English