Building blocks of a flip-chip integrated superconducting quantum processor

Abstract

We have integrated single and coupled superconducting transmon qubits into flip-chip modules. Each module consists of two chips - one quantum chip and one control chip - that are bump-bonded together. We demonstrate time-averaged coherence times exceeding 90μs, single-qubit gate fidelities exceeding 99.9%, and two-qubit gate fidelities above 98.6%. We also present device design methods and discuss the sensitivity of device parameters to variation in interchip spacing. Notably, the additional flip-chip fabrication steps do not degrade the qubit performance compared to our baseline state-of-the-art in single-chip, planar circuits. This integration technique can be extended to the realisation of quantum processors accommodating hundreds of qubits in one module as it offers adequate input/output wiring access to all qubits and couplers.

Qubit-Compatible Substrates With Superconducting Through-Silicon Vias

“…Flip-chip bonded modules of two chips connected by superconducting bumps increase the layer count to two and air bridges further alleviate routing challenges. These have indeed been used successfully to construct processors of several dozen qubits [9]- [11], although with coherence times and gate fidelities significantly lower than in planar [12]- [16] or flip-chip bonded [17] single-or few-qubit devices.…”

“…Yost et al [21], [22] have on the other hand demonstrated through-silicon vias (TSVs) that have a relatively high aspect ratio and high critical currents, and show promise in terms of not destroying qubit coherence, as the demonstrated qubit relaxation time of 12.5 µs [21] and resonator internal quality factors of 10 5 to 2 × 10 5 [22] were identified to be limited by factors unrelated to TSVs. For comparison, widelyreproduced relaxation times for transmon qubits on silicon substrates are near 50 µs [12]- [17]. In addition, Gordon et al have reported relaxation times of hundreds of µs [4].…”

Enhancing the Coherence of Superconducting Quantum Bits with Electric Fields

“…Figure 4 shows a possible implementation of a gate electrode array, which is located on a separate wiring chip that is bumb-bonded to the chip carrying the qubits in a flip-chip configuration 36,37 . In Fig.…”

Transmon qubit readout fidelity at the threshold for quantum error correction without a quantum-limited amplifier

“…The device design and fabrication is described in Ref. [38] with the circuit schematic shown in Fig. 1.…”

“…The device design and fabrication is described in Ref. [38] with the circuit schematic shown in Fig. device consists of three fixed-frequency transmon qubits [39] with transition frequencies ω qi /2π at 5.36, 5.40, and 5.46 GHz for i = 1, 2, 3, respectively.…”