Toward Scalable Superconducting Quantum Computer Implementation

Tabuchi, Yoshihiko; Tamate, Shuhei; Nakamura, Y.

doi:10.1587/transele.2018sdp0001

Cited by 5 publications

(6 citation statements)

References 22 publications

(32 reference statements)

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“…Ground planes are electrically connected via bumps fabricated by ip-chip bonding. Figure 7a shows the layout for the transmon qubits 28,29 and the CQ, where parts of the circuit face each other to create indirect coupling. Figure 7b shows the equivalent circuit, where the interconnection is controlled by applying the transverse magnetic ux to the CQ through I trans_CQ .…”

Section: Discussionmentioning

confidence: 99%

Scalable Interconnection Using a Superconducting Flux Qubit

Saida

Hidaka

Makise

2023

Preprint

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To improve the performance of quantum computers, implementation technology that guarantees the scalability of the number of qubits is essential, and increasing the degrees of freedom in routing by 2.5-dimensional implementation is important for realizing the scalability of circuits. Here, we achieve long-distance coupling using a superconducting flux qubit enabling routing on the order of millimeters. We report the design for a reliable connection qubit with a proof-of-concept demonstration of quantum annealing. We perform experiments and simulations on suppressing errors due to coupling. The coupling status is strictly controllable, enabling elimination of crosstalk from the unintentional circuit region. A low-temperature flip-chip bonding technology is introduced for the 2.5-dimensional interconnection. The superconducting flux qubit, formed across two different chips via bumps, is demonstrated for the first time to show a state transition similar to that in a conventional qubit. The connection qubit and flip-chip bonding pave the way for new interconnections between different types of qubits. The possibility of interactions between gate-type qubits is investigated in a simulation.

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Section: Discussionmentioning

confidence: 99%

Scalable Interconnection Using a Superconducting Flux Qubit

Saida

Hidaka

Makise

2023

Preprint

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“…Two other scalable 3D-integration approaches are multi-chip (flip-chip or interposer chip) circuits and out-of-plane wiring [1,2,[8][9][10][11][12][13][14][15][16]. Both approaches have the advantage that the chip hosting the quantum circuitry can be fabricated separately, with minimal extra processing that risks degrading qubit performance.…”

Section: Introductionmentioning

confidence: 99%

“…Out-of-plane wiring implementations eliminate the need for multiple chips, but instead deploy, e.g., spring-loaded [13][14][15] or coaxial [16] pins that approach the chip perpendicularly. Such implementations yield direct access to components within the two-dimensional qubit array, obviating the need of routing from the edges of the chip.…”

Section: Introductionmentioning

confidence: 99%

Building blocks of a flip-chip integrated superconducting quantum processor

Kosen

Rommel

et al. 2022

Quantum Sci. Technol.

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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.

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“…12,13) Among these implementations, superconducting quantum computers have advantages in their scalability and availability. 14,15) On the other hand, qubit inhomogeneity coming from the fabrication process of Josephson junctions is one of the biggest problem in scaling up superconducting quantum computers. The performance of superconducting qubits is strongly influenced by defects and surface contaminations around Josephson junctions (JJs).…”

Section: Introductionmentioning

confidence: 99%

Uniformity improvement of Josephson-junction resistance by considering sidewall deposition during shadow evaporation for large-scale integration of qubits

Takahashi

Kouma

Doi

et al. 2022

Jpn. J. Appl. Phys.

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The uniformity of Josephson-junction (JJ) characteristics is crucial in wafer-scale superconducting quantum-bit (qubit) integration. To achieve the level of accuracy demanded the circuits, every detail of the fabrication process needs to be optimized. Here we reveal that the junction-resistance (RN) variations of Al/AlOx/Al JJs are affected by the metal deposition on the sidewall of the resist mask during shadow evaporation. The effect is reproduced in numerical simulation using a simple model taking into account the resist structure and the evaporation angle. To overcome the issue, we introduce a two-step shadow evaporation method to reduce the variation of RN. As a result, the coefficient of variations across a 3-inch wafer decreases from 6.7% to 4.5%, achieving 1.1% in a chip with an area of 10 mm × 10 mm. This method is promising for developing large-scale superconducting quantum computers.

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Toward Scalable Superconducting Quantum Computer Implementation

Cited by 5 publications

References 22 publications

Scalable Interconnection Using a Superconducting Flux Qubit

Scalable Interconnection Using a Superconducting Flux Qubit

Building blocks of a flip-chip integrated superconducting quantum processor

Uniformity improvement of Josephson-junction resistance by considering sidewall deposition during shadow evaporation for large-scale integration of qubits

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