The Compact High-Coherence Superconducting Qubit: Realization via Meander-Shaped Capacitor

Qing Mu; Zhiguo Zha; Yonglong Shen; Chuanbing Han; Fudong Liu; Bo Zhao; Chaojie Zhang; Yimin Gao; Wenlong Yu; Xiao Cai; Yu Wang; Zheng Shan

doi:10.1016/j.eng.2026.05.011

Engineering ›› :202605011 DOI: 10.1016/j.eng.2026.05.011

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The Compact High-Coherence Superconducting Qubit: Realization via Meander-Shaped Capacitor

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Abstract

Scalable superconducting qubit architectures demand qubits with long coherence times—a critical prerequisite for developing practical quantum computers. To achieve a compact circuit footprint, we have designed a superconducting qubit featuring a meander-structured coplanar waveguide capacitor, termed the “Smon.” Numerical simulations of the electric field distribution demonstrate that the Smon exhibits a significantly lower energy participation ratio (EPR) than both Xmon qubits and conventional rectangular planar transmon qubits. For an in situ comparison between Smons and conventional rectangular planar transmons, we propose a two-dimensional (2D) hybrid qubit array test structure. The capacitor electrodes of the devices are fabricated using tantalum. Measurements of the Smon’s coherence properties yield an energy relaxation time (T₁) ranging from 30 to 359 µs and a dephasing time (T₂) between 18 and 20 µs. These results confirm that superconducting quantum circuits with enhanced integration density and long coherence times are experimentally feasible, thereby offering a viable pathway toward high-performance large-scale superconducting quantum computers.

Keywords

Superconducting qubits / Electromagnetic simulation / Transmon / Smon / High coherence

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Qing Mu, Zhiguo Zha, Yonglong Shen, Chuanbing Han, Fudong Liu, Bo Zhao, Chaojie Zhang, Yimin Gao, Wenlong Yu, Xiao Cai, Yu Wang, Zheng Shan. The Compact High-Coherence Superconducting Qubit: Realization via Meander-Shaped Capacitor. Engineering 202605011 DOI:10.1016/j.eng.2026.05.011

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References

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[1]	Tuokkola M, Sunada Y, Kivijärvi H, Albanese J, Grönberg L, Kaikkonen JP, et al. Methods to achieve near—millisecond energy relaxation and dephasing times for a superconducting transmon qubit. Nat Commun 2025; 16:5421.

[2]	Koch J, Yu TM, Gambetta J, Houck AA, Schuster DI, Majer J, et al. Charge—insensitive qubit design derived from the cooper pair box. Phys Rev A 2007; 76(4):042319.

[3]	Arute F, Arya K, Babbush R, Bacon D, Bardin JC, Barends R, et al. Quantum supremacy using a programmable superconducting processor. Nature 2019; 574(7779):505—10.

[4]	Barends R, Kelly J, Megrant A, Sank D, Jeffrey E, Chen Y, et al. Coherent Josephson qubit suitable for scalable quantum integrated circuits. Phys Rev Lett 2013; 111(8):080502.

[5]	Bland MP, Bahrami F, Martinez JG, Prestegaard PH, Smitham BM, Joshi A, et al. 2D transmons with lifetimes and coherence times exceeding 1 millisecond. 2025. arXiv:2503.14798.

[6]	Somoroff A, Ficheux Q, Mencia RA, Xiong H, Kuzmin R, Manucharyan VE . Millisecond coherence in a superconducting qubit. Phys Rev Lett 2023; 130(26):267001.

[7]	Hyyppä E, Kundu S, Chan CF, Gunyhó A, Hotari J, Janzso D, et al. Unimon qubit. Nat Commun 2022; 13(1):6895.

[8]	Duda R, Hyyppä E, Mukkula O, Vadimov V, Möttönen M . Parameter optimization for the unimon qubit. Phys Rev Res 2025; 7(3):033092.

[9]	Kim H, Jang G, Jin S, Shin D, Shin HJ, Luo J, et al. Josephson junctions in the age of quantum discovery. 2025. arXiv:2505.12724.

[10]	Keller AJ, Dieterle PB, Fang M, Berger B, Fink JM, Painter O . Superconducting qubits on silicon substrates for quantum device integration. 2017. arXiv:1703.101953.

[11]	Bruno A, De Lange G, Asaad S, van der Enden KL, Langford NK, DiCarlo L . Reducing intrinsic loss in superconducting resonators by surface treatment and deep etching of silicon substrates. Appl Phys Lett 2015; 106(18):182601.

[12]	Megrant A, Neill C, Barends R, Chiaro B, Chen Y, Feigl L, et al. Planar superconducting resonators with internal quality factors above one million. Appl Phys Lett 2012; 100(11):113510.

[13]	Goswami A, McFadden AP, Zhao T, Inbar H, Dong JT, Zhao R, et al. Towards merged—element transmons using silicon fins: the FinMET. Appl Phys Lett 2022; 121(6):064001.

[14]	Zheng L, Chen M, Sun Z, Ko HY, Santra B, Dhuvad P, et al. Structural, electronic, and dynamical properties of liquid water by ab initio molecular dynamics based on SCAN functional within the canonical ensemble. J Chem Phys 2018; 148(16):164505.

[15]	Dunsworth A, Barends R, Chen Y, Chen Z, Chiaro B, Fowler A, et al. A method for building low loss multi—layer wiring for superconducting microwave devices. Appl Phys Lett 2018; 112(6):063502.

[16]	Tex DM, Imaizumi M, Kanemitsu Y . Analyzing the electrical performance of a solar cell with time—resolved photoluminescence: methodology for fast optical screening. Phys Rev Appl 2017; 7(1):014019.

[17]	Zhao R, Park S, Zhao T, Bal M, McRae CRH, Long J, et al. Merged—element transmon. Phys Rev Appl 2020; 14(6):064006.

[18]	Mamin H, Huang E, Carnevale S, Rettner CT, Arellano N, Sherwood MH, et al. Merged—element transmons: design and qubit performance. Phys Rev Appl 2021; 16(2):024023.

[19]	Li X, Zhang Y, Yang C, Li Z, Wang J, Su T, et al. Vacuum—gap transmon qubits realized using flip—chip technology. Appl Phys Lett 2021; 119(18):184003.

[20]	Wang C, Axline C, Gao YY, Brecht T, Chu Y, Frunzio L, et al. Surface participation and dielectric loss in superconducting qubits. Appl Phys Lett 2015; 107(16):162601.

[21]	Martinis JM . Surface loss calculations and design of a superconducting transmon qubit with tapered wiring. npj Quantum Inf 2022; 8(1):26.

[22]	He H, Wang W, Liu F, Yuan B, Shan Z . Suppressing the dielectric loss in superconducting qubits through useful geometry design. Entropy 2022; 24(7):952.

[23]	Martinis JM, Cooper KB, McDermott R, Steffen M, Ansmann M, Osborn KD, et al. Decoherence in Josephson qubits from dielectric loss. Phys Rev Lett 2005; 95(21):210503.

[24]	Lisenfeld J, Bilmes A, Megrant A, Barends R, Kelly J, Klimov P, et al. Electric field spectroscopy of material defects in transmon qubits. npj Quantum Inf 2019; 5(1):105.

[25]	Place APM, Rodgers LVH, Mundada P, Smitham BM, Fitzpatrick M, Leng Z, et al. New material platform for superconducting transmon qubits with coherence times exceeding 0.3 milliseconds. Nat Commun 2021; 12(1):1779.

[26]	Yuan B, Wang W, Liu F, He H, Shan Z . Comparison of lumped oscillator model and energy participation ratio methods in designing two—dimensional superconducting quantum chips. Entropy 2022; 24(6):792.

[27]	Dial O, McClure DT, Poletto S, Keefe GA, Rothwell MB, Gambetta JM, et al. Bulk and surface loss in superconducting transmon qubits. Supercond Sci Technol 2016; 29(4):044001.

[28]	Gambetta JM, Murray CE, Fung YKK, McClure DT, Dial O, Shanks W, et al. Investigating surface loss effects in superconducting transmon qubits. IEEE Trans Appl Supercond 2017; 27(1):1-5.

[29]	Zhang C, Wang W, Li J, Yuan B, Yu X, Zha Z, et al. Optimization of superconducting qubit capacitor geometry based on deep reinforcement learning. Quantum Inform Process 2026; 25(2):68.

[30]	PourhosseiniAsl MJ, Yu Z, Chu Z, Yang J, Xu JJ, Hou Y, et al. Enhanced self—bias magnetoelectric effect in locally heat—treated me laminated composite. Appl Phys Lett 2019; 115(11):112901.

[31]	Paik H, Schuster DI, Bishop LS, Kirchmair G, Catelani G, Sears AP, et al. Observation of high coherence in Josephson junction qubits measured in a three—dimensional circuit QED architecture. Phys Rev Lett 2011; 107(24):240501.