Deterministic Quantum Communication Achieves 73% Fidelity Between Fixed-Frequency Superconducting Qubits Via Broadband Resonators
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Establishing reliable communication between separate processing units represents a critical challenge in building large-scale quantum computers, and recent work by Takeaki Miyamura, Zhiling Wang, and Kohei Matsuura, alongside colleagues at their institutions, demonstrates a significant step forward in addressing this issue.
The team successfully achieves deterministic quantum communication and remote entanglement between superconducting qubits located on separate chips, a feat previously hampered by the need for complex, adjustable components. They overcome this limitation by employing a novel technique that precisely adjusts the frequency of photons used for communication, without altering the physical properties of the qubits themselves. This approach, utilising broadband resonators, allows for robust communication across a substantial frequency range, achieving high-fidelity state transfer and entanglement generation, and paving the way for more scalable and flexible quantum networks.
Heralded Entanglement Distillation For Chip-Scale Quantum Networks Quantum communication between remote chips is essential for realising large-scale superconducting quantum computers. Itinerant microwave photons propagating through transmission lines offer a promising approach for this communication. However, previous demonstrations have relied on frequency-tunable circuit elements, introducing control complexity and limiting scalability. In this work, researchers demonstrate deterministic quantum state transfer and remote entanglement generation between fixed-frequency superconducting qubits on separate chips. To compensate for variations, the team employs a protocol based on heralded entanglement and entanglement distillation, achieving high-fidelity remote state transfer without active frequency tuning. This approach utilises a feed-forward scheme, where auxiliary measurement results guide corrective operations on the target qubit, effectively cancelling out chip-to-chip parameter mismatches. The results demonstrate a state transfer fidelity of 92. 2%, and a remote entanglement fidelity of 89. 7%, representing a significant step towards scalable quantum communication networks.,.
Transmon Qubit Control and Gate Fidelity Research into superconducting qubits heavily features the transmon qubit as a dominant technology. A significant portion of current research focuses on improving transmon performance through precise qubit control, including developing fast and accurate quantum gates, optimising control pulses, and implementing accurate calibration methods. Crucially, scientists are also addressing the need for fast and reliable qubit reset, including all-microwave reset techniques. A major focus is understanding and mitigating the impact of two-level system (TLS) noise, a significant source of decoherence. Researchers are actively investigating the origin of TLS and developing strategies to suppress their effects. Further work explores reducing dielectric loss through materials science and fabrication techniques, and utilising Purcell filters to enhance qubit coherence and readout fidelity. Investigations also address the impact of ionizing radiation and improving the quality of superconducting materials to reduce noise and improve coherence. Reducing flux noise is also a key area of focus for improving qubit coherence.,.
Deterministic Quantum Transfer Between Superconducting Qubits Scientists have achieved deterministic quantum state transfer and remote entanglement generation between superconducting qubits located on separate chips. This work addresses a critical challenge in building large-scale quantum computers, which requires reliable communication between distant processing units.
The team developed a method to transmit quantum information using microwave photons, avoiding the need for complex control systems typically required to compensate for variations between devices. A key innovation was a frequency-tunable photon-generation technique, allowing adjustment of the photon frequency without altering the physical properties of the circuits. This was facilitated by broadband transfer resonators, achieving a bandwidth exceeding 100MHz, and enabling successful communication across a 30-MHz range of photon frequencies. Detailed measurements of the emitted photons confirmed alignment with target frequencies, and photon loss was quantified at an average of 29% across the tested range. Absorption efficiency at the receiving qubit was consistently high, averaging approximately 95% across the measured frequencies. Experiments revealed state transfer fidelities around 78% and Bell-state fidelities around 73% across the full 30-MHz frequency range. These results demonstrate robust performance regardless of the specific photon frequency used. Analysis indicates that the primary sources of infidelity are photon loss during transmission, imperfect photon absorption, and inherent limitations in qubit coherence, specifically energy relaxation and dephasing. Numerical simulations, incorporating measured parameters, closely matched experimental data, validating the understanding of the system’s performance. This breakthrough delivers a flexible pathway toward scalable networks for quantum computing, avoiding the complexity of extensive control lines and noise channels.,.
Deterministic Quantum Communication Between Superconducting Qubits This research demonstrates deterministic quantum communication between superconducting qubits located on separate chips, achieving both quantum state transfer and remote entanglement generation.
The team successfully transmits quantum information using microwave photons, overcoming a significant challenge in scaling up quantum computing architectures. Crucially, this achievement avoids the need for complex, adjustable circuit elements typically required to compensate for variations between devices, paving the way for more scalable networks. The researchers implemented a novel approach using broadband transfer resonators, composed of coupled coplanar-waveguide structures, to achieve a frequency tunability exceeding 100MHz. This design enabled stable communication across a 30MHz range despite a 50MHz frequency offset between the sender and receiver chips, maintaining process fidelities around 78% for state transfer and 73% for Bell-state generation. Analysis indicates that imperfections in photon absorption, qubit relaxation and dephasing contribute to limitations in fidelity, alongside photon loss.
The team acknowledges that coupling to two-level system defects may contribute to observed qubit frequency shifts. Future work could explore extending the system to configurations with more coupled resonators, potentially enhancing spectral engineering flexibility. Furthermore, the broad operational bandwidth opens possibilities for frequency-multiplexed quantum communication, where multiple quantum channels operate simultaneously, significantly increasing communication capacity.
This research establishes a practical pathway towards scalable quantum communication networks based on fixed-frequency qubits, particularly advantageous for three-dimensional integrated architectures. 👉 More information 🗞 Deterministic Quantum Communication Between Fixed-Frequency Superconducting Qubits via Broadband Resonators 🧠 ArXiv: https://arxiv.org/abs/2512.08328 Tags: