Scalable Optical Links Enable Control of Bosonic Quantum Processors with up to Ten Photons
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Superconducting quantum computing promises transformative capabilities, but building larger, more powerful processors faces a significant hurdle: the limitations of traditional electrical connections. Chuanlong Ma, Jia-Qi Wang, and Linze Li, along with colleagues including Zheng-Hui Tian, have overcome a key obstacle by demonstrating scalable optical links for controlling a complex quantum processor.
The team achieves universal control over both a superconducting qubit and a storage cavity, utilising light to prepare quantum states containing up to ten photons and transmitting control signals over a remarkable distance of 15km with over 95% fidelity. This breakthrough addresses critical challenges in scaling quantum systems, paving the way for advanced architectures and potentially enabling the development of distributed quantum data centres.
Superconducting Qubit Control and Interconnect Research Superconducting quantum computing holds immense potential for revolutionising computational capabilities, but scaling up these processors faces significant challenges. Traditional electronic cables connecting room-temperature control electronics to quantum processors introduce substantial signal attenuation and heat, hindering performance. Researchers are now exploring optical fibres as a promising solution, offering a pathway to overcome these limitations and build larger, more powerful quantum computers. This body of work details advancements in superconducting qubits and the development of optical and photonic interconnects designed to scale these systems. A core focus lies in circuit quantum electrodynamics, the dominant platform for superconducting qubits, involving the coupling of superconducting circuits to microwave resonators. Scientists are continually refining qubit design and control techniques, improving coherence, gate fidelity, and exploring different qubit types. A key objective is moving beyond individual physical qubits to create logical qubits, which are more robust to errors through encoding and correction schemes. Maintaining qubit coherence for extended periods is also vital, with progress demonstrated in achieving millisecond coherence times essential for complex quantum computations. Scaling quantum computers requires connecting many qubits, and traditional wiring quickly becomes impractical.
This research highlights the growing interest in using optical interconnects to transmit quantum information. Optical fibres offer several advantages, including low signal loss, high bandwidth capacity, and reduced wiring complexity. Scientists are developing electro-optic modulators and utilising materials like lithium niobate to control and manipulate light signals. Silicon photonics is also being employed to create integrated optical circuits that guide and manipulate light on a chip. Techniques like frequency combs and wavelength division multiplexing are being explored to increase the capacity of these optical interconnects.
This research extends to the broader field of quantum communication and networking, exploring concepts like distributed quantum computing, where multiple smaller quantum processors are connected. The development of optical interconnects is a crucial step towards enabling quantum communication and entanglement distribution between distant quantum processors. Researchers are also focused on advanced measurement and characterisation techniques, such as quantum tomography. The combination of superconducting qubits with photonic interconnects represents a promising approach to building scalable quantum computers, with a strong push towards integrated photonics for reduced size, cost, and complexity. Optical Control of Superconducting Quantum Systems This work demonstrates a significant advancement in controlling superconducting quantum systems through the development of an integrated optical link. Researchers successfully implemented universal operations on a system combining a transmon qubit and a storage cavity, overcoming limitations imposed by traditional microwave cabling. A key achievement is the fabrication and implementation of an array of cryogenic fiber-integrated uni-traveling-carrier photodiodes, enabling the preparation of Fock states containing up to ten photons. This approach dramatically reduces signal attenuation, with optical fibres exhibiting a loss of only 0. 2 dB/km, a figure nearly four orders of magnitude lower than the approximately 1000 dB/km experienced with coaxial cables at 6GHz. This low attenuation allows for long-distance control, with remote operation achieved over a transmission distance of 15km while maintaining fidelities exceeding 95%. Measurements confirm the system’s ability to independently control components of the bosonic quantum processor, including the transmon qubit, readout resonator, and storage cavity. Detailed analysis of the system dynamics reveals precise control over the quantum state.
Optical Fiber Links Enable Quantum Control This research demonstrates a significant advance in superconducting quantum technology through the successful implementation of optical fibre links for controlling a complex quantum processor. Researchers achieved universal control of a system combining a transmon qubit and a storage cavity, preparing quantum states containing up to ten photons with high precision. Crucially, this control was maintained over a transmission distance of 15 kilometres, with operation fidelities consistently exceeding 95%. This achievement overcomes a key limitation in scaling quantum computers, which is the signal attenuation caused by traditional electronic cabling. The results establish that optical links support high-precision operations on complex, high-dimensional quantum systems, moving beyond the control of simple two-level qubits. This approach offers multiple advantages for large-scale quantum computation, including the ability to distribute control signals across multiple processors with minimal latency, reduced thermal load and space requirements within cryogenic environments, and the potential for cost-effective industrial-scale manufacturing.
The team anticipates improvements through the incorporation of advanced optical technologies, such as microcomb sources and wavelength-division multiplexing. 👉 More information 🗞 Scalable Optical Links for Controlling Bosonic Quantum Processors 🧠 ArXiv: https://arxiv.org/abs/2512.10706 Tags: