ZZ-Free Two-Transmon CZ Gate Mediated by a Fluxonium Coupler

• URL: http://arxiv.org/abs/2511.02115v1
• Date: Mon, 03 Nov 2025 23:03:25 GMT
• Title: ZZ-Free Two-Transmon CZ Gate Mediated by a Fluxonium Coupler
• Authors: Junyoung An, Helin Zhang, Qi Ding, Leon Ding, Youngkyu Sung, Roni Winik, Junghyun Kim, Ilan T. Rosen, Kate Azar, Renee DePencier Piñero, Jeffrey M. Gertler, Michael Gingras, Bethany M. Niedzielski, Hannah Stickler, Mollie E. Schwartz, Joel Î-j. Wang, Terry P. Orlando, Simon Gustavsson, Max Hays, Jeffrey A. Grover, Kyle Serniak, William D. Oliver,
• Abstract summary: Eliminating residual ZZ interactions in a two-qubit system is essential for reducing coherent errors during quantum operations.<n>We introduce TFT (Transmon-Fluxonium-Transmon) architecture, wherein two transmon qubits are coupled via a fluxonium qubit.<n>We experimentally identified zero-ZZ interaction points at qubit-qubit detunings of 409 MHz and 616 MHz from two distinct TFT devices.
• Score: 1.120432826505191
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Eliminating residual ZZ interactions in a two-qubit system is essential for reducing coherent errors during quantum operations. In a superconducting circuit platform, coupling two transmon qubits via a transmon coupler has been shown to effectively suppress residual ZZ interactions. However, in such systems, perfect cancellation usually requires the qubit-qubit detuning to be smaller than the individual qubit anharmonicities, which exacerbates frequency crowding and microwave crosstalk. To address this limitation, we introduce TFT (Transmon-Fluxonium-Transmon) architecture, wherein two transmon qubits are coupled via a fluxonium qubit. The coupling mediated by the fluxonium eliminates residual ZZ interactions even for transmons detuned larger than their anharmonicities. We experimentally identified zero-ZZ interaction points at qubit-qubit detunings of 409 MHz and 616 MHz from two distinct TFT devices. We then implemented an adiabatic, coupler-flux-biased controlled-Z gate on both devices, achieving CZ gate fidelities of 99.64(6)% and 99.68(8)%.

Related papers

• High-fidelity all-microwave CZ gate with partial erasure-error detection via a transmon coupler [1.5649495995972291]
  Entangling gates between neighboring physical qubits are essential for quantum error correction.<n>We show an all-microwave controlled-Z (CZ) gate that achieves high fidelity while suppressing residual ZZ interactions.
  arXiv  Detail & Related papers  (2025-11-03T06:11:18Z)
• Tunable Superconducting Quantum Interference Device Coupler for Fluxonium Qubits [0.8691965235932587]
  Tunable couplers enable high-fidelity two-qubit gates leveraging high on/off coupling ratios and reduced crosstalk within a single design.<n>We present two schemes to implement two-qubit gates, predicting a $sqrtitextSWAP$-like gate with $99.9%$ open-system fidelity in less than 6 nanoseconds.
  arXiv  Detail & Related papers  (2025-08-23T05:42:59Z)
• Cross-talk in superconducting qubit lattices with tunable couplers - comparing transmon and fluxonium architectures [0.0]
  Cross-talk between qubits is one of the main challenges for scaling superconducting quantum processors.<n>We compare different architectures that include tunable couplers designed to decouple qubits in the idle state.<n>For transmon qubits outside of the straddling regime, the results confirm that tunable C-shunt flux couplers are significantly more efficient in mitigating the ZZ interactions than tunable transmons.
  arXiv  Detail & Related papers  (2025-04-14T15:07:35Z)
• Resonator-assisted quantum transduction between superconducting qubits and trapped atomic systems via Rydberg levels [45.88028371034407]
  We propose a scheme between superconducting qubits and qubit states encoded in trapped atomic systems.<n>The approach employs atomic Rydberg levels together with laser pulses that connect them to the low-lying qubit states.
  arXiv  Detail & Related papers  (2025-01-06T18:28:18Z)
• Realization of two-qubit gates and multi-body entanglement states in an asymmetric superconducting circuits [3.9488862168263412]
  We propose a tunable fluxonium-transmon-transmon (FTT) cou pling scheme. The asymmetric structure composed of fluxonium and transmon will optimize the frequency space and form a high fidelity two-qubit quantum gate. We study the performance of this scheme by simulating the general single-qubit Xpi/2 gate and two-qubit (iSWAP) gate.
  arXiv  Detail & Related papers  (2024-04-12T08:44:21Z)
• Fast ZZ-Free Entangling Gates for Superconducting Qubits Assisted by a Driven Resonator [42.152052307404]
  We propose a simple scheme to cancel stray interactions between qubits. We numerically show that such a scheme can enable short and high-fidelity entangling gates. Our architecture is not only ZZ free but also contains no extra noisy components.
  arXiv  Detail & Related papers  (2023-11-02T15:42:02Z)
• Two qubits in one transmon -- QEC without ancilla hardware [68.8204255655161]
  We show that it is theoretically possible to use higher energy levels for storing and controlling two qubits within a superconducting transmon. The additional qubits could be used in algorithms which need many short-living qubits in error correction or by embedding effecitve higher connectivity in qubit networks.
  arXiv  Detail & Related papers  (2023-02-28T16:18:00Z)
• Coupler microwave-activated controlled phase gate on fluxonium qubits [32.73124984242397]
  A tunable coupler typically includes a nonlinear element, such as a SQUID, which is used to tune the resonance frequency of an LC circuit connecting two qubits. Here we propose a complimentary approach where instead of tuning the resonance frequency of the tunable coupler by applying a quasistatic control signal, we excite by microwave the degree of freedom associated with the coupler itself.
  arXiv  Detail & Related papers  (2023-02-20T07:51:04Z)
• Stabilizing and improving qubit coherence by engineering noise spectrum of two-level systems [52.77024349608834]
  Superconducting circuits are a leading platform for quantum computing. Charge fluctuators inside amorphous oxide layers contribute to both low-frequency $1/f$ charge noise and high-frequency dielectric loss. We propose to mitigate those harmful effects by engineering the relevant TLS noise spectral densities.
  arXiv  Detail & Related papers  (2022-06-21T18:37:38Z)
• Microwave-activated gates between a fluxonium and a transmon qubit [59.95978973946985]
  We propose and analyze two types of microwave-activated gates between a fluxonium and a transmon qubit. For a medium-frequency fluxonium qubit, the transmon-fluxonium system allows for a cross-resonance effect mediated by the higher levels of the fluxonium. A fast microwave CPHASE gate can be implemented using the higher levels of the fluxonium.
  arXiv  Detail & Related papers  (2022-06-13T14:34:11Z)
• High fidelity two-qubit gates on fluxoniums using a tunable coupler [47.187609203210705]
  Superconducting fluxonium qubits provide a promising alternative to transmons on the path toward large-scale quantum computing. A major challenge for multi-qubit fluxonium devices is the experimental demonstration of a scalable crosstalk-free multi-qubit architecture. Here, we present a two-qubit fluxonium-based quantum processor with a tunable coupler element.
  arXiv  Detail & Related papers  (2022-03-30T13:44:52Z)
• Superconducting coupler with exponentially large on-off ratio [68.8204255655161]
  Tunable two-qubit couplers offer an avenue to mitigate errors in multiqubit superconducting quantum processors. Most couplers operate in a narrow frequency band and target specific couplings, such as the spurious $ZZ$ interaction. We introduce a superconducting coupler that alleviates these limitations by suppressing all two-qubit interactions with an exponentially large on-off ratio.
  arXiv  Detail & Related papers  (2021-07-21T03:03:13Z)
• Fast parametric two-qubit gates with suppressed residual interaction using a parity-violated superconducting qubit [0.0]
  Two-qubit gates are demonstrated using a superconducting qubit consisting of a capacitively-shunted asymmetric Josephson-junction loop under a finite magnetic flux bias. The average fidelities of the two-qubit gates are evaluated with randomized benchmarking frequencies as 0.967, 0.951, 0.956 for CZ, iSWAP and SWAP gates, respectively.
  arXiv  Detail & Related papers  (2020-05-06T07:29:23Z)
• Universal non-adiabatic control of small-gap superconducting qubits [47.187609203210705]
  We introduce a superconducting composite qubit formed from two capacitively coupled transmon qubits. We control this low-frequency CQB using solely baseband pulses, non-adiabatic transitions, and coherent Landau-Zener interference. This work demonstrates that universal non-adiabatic control of low-frequency qubits is feasible using solely baseband pulses.
  arXiv  Detail & Related papers  (2020-03-29T22:48:34Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.