Tantalum Thin Film Enables On-Demand Microwave Single-Photon Source for Information Technologies
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Single-photon sources represent a vital component in the development of advanced information technologies, and researchers are continually seeking materials that enable efficient and stable photon emission. Ying Hu, Sheng-Yong Li, and En-Qi Chen, from Hunan Normal University, alongside Jing Zhang from Xi’an Jiaotong University, Yu-xi Liu from Tsinghua University, and Jia-Gui Feng et al. from the Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, have now created a source utilising a tantalum-based thin film. This innovative approach yields high-quality single photons and exhibits clear antibunching behaviour, a key characteristic confirming the emission of individual photons. By incorporating travelling-wave parametric amplifiers into the detection system, the team significantly enhances signal clarity and reduces measurement times, demonstrating the potential of tantalum-based superconducting devices as robust platforms for future microwave photonics applications. Superconducting Qubits, Circuit QED, and Photonics This extensive collection of research papers details advancements in superconducting qubits, circuit quantum electrodynamics, and quantum photonics. The body of work focuses on improving qubit performance, exploring the interaction between qubits and microwave photons, and developing technologies for quantum communication and networking. Key areas of investigation include qubit design, materials science, and the creation of efficient single-photon sources and detectors, collectively aiming to build the foundations for scalable and practical quantum technologies. A significant portion of the research concentrates on enhancing qubit coherence and reducing decoherence, exploring various qubit designs such as transmons, flux qubits, and charge qubits. Crucially, materials science plays a central role, with investigations into tantalum, niobium films, and oxides to optimize qubit performance and achieve reproducible characteristics. The research also explores circuit QED, focusing on the strong coupling between superconducting qubits and microwave photons, essential for quantum information processing. Generating, manipulating, and detecting single microwave photons is another key theme, vital for building quantum networks and enabling long-distance quantum communication. Researchers are demonstrating the ability to create and measure quantum correlations between photons and qubits, utilizing techniques like Hanbury Brown-Twiss correlations and Hong-Ou-Mandel interference. The increasing emphasis on single-photon sources and detectors suggests a growing interest in using microwave photons as carriers of quantum information for long-distance communication and networking.
Tantalum Transmon Qubit for Microwave Photon Emission Researchers engineered a novel microwave single-photon source using a tantalum-based thin film. Devices were fabricated on sapphire wafers, undergoing rigorous cleaning with acetone, isopropyl alcohol, and piranha solution to ensure stability and minimize microwave loss. Photolithography defined the patterns for capacitors, resonators, and drive lines, followed by wet etching to remove unwanted tantalum, a process crucial for mitigating substrate damage. The core of the source is a transmon qubit, strongly coupled to both a coplanar-waveguide resonator and a transmission waveguide, enabling tunable frequency emission. Experiments were conducted within a dilution refrigerator, cooling the sample to a base temperature of 18mK and shielding it with multiple layers of mu-metal and aluminum to minimize external interference. A sophisticated measurement scheme employed attenuators distributed across the refrigerator stages to suppress thermal noise and prevent unwanted qubit excitation, while a 4-12GHz circulator allowed direct characterization of the source’s performance. The emitted signal was split into two channels using a 1-12GHz hybrid coupler, forming a Hanbury Brown-Twiss-type setup to measure emission dynamics and correlation functions. To substantially improve signal-to-noise ratio, the team integrated traveling-wave parametric amplifiers (TWPAs) as pre-amplifiers in each detection channel, achieving an order-of-magnitude improvement over conventional systems and significantly reducing required averaging time. Isolators, strategically placed at input and output ports of the TWPA and in front of a high electron mobility transistor (HEMT), protected the amplifiers from back action and ensured stable operation. The total gain of the output line reached approximately 75dB, with 38dB from the HEMT and 37dB from room-temperature amplifiers. Heterodyne detection, facilitated by amplifiers at various temperature stages, enabled precise time-domain and correlation measurements.
Tantalum Film Emits Stable Single Photons Scientists have demonstrated a novel microwave single-photon source fabricated from a tantalum-based thin film, achieving stable and high-quality photon emission. The research team successfully measured sub-Poissonian photon statistics, confirming antibunched emission through detailed correlation measurements, a key characteristic of single-photon sources. Analysis using X-ray diffraction revealed the crystalline structure of the tantalum film, identifying prominent peaks corresponding to the (110) and (220) orientations, and confirming the quality of the deposited material. Further characterization of the film’s electrical properties showed a clear superconducting transition at 4. 22 Kelvin, indicating the material’s suitability for quantum circuit applications.
The team employed traveling-wave parametric amplifiers (TWPAs) as low-noise pre-amplifiers within the detection chain, substantially enhancing the signal-to-noise ratio during pulsed single-photon detection. This innovative approach significantly reduced the averaging time required for second-order correlation measurements, a critical advancement for efficient characterization of single-photon emission. Atomic force microscopy revealed the surface morphology of the tantalum film, demonstrating a smooth and uniform structure essential for device performance. The researchers observed a dense amorphous tantalum oxide passivation layer forming on the film’s surface during processing, contributing to the material’s stability and minimal aging effects on resonator quality. Measurements confirmed the superconducting properties of the tantalum film, with resistance dropping sharply at the critical temperature, demonstrating its potential for building high-performance quantum circuits. The implementation of this tantalum-based single-photon source, coupled with advanced amplification techniques, represents a significant step towards realizing practical microwave quantum photonics and enabling advancements in superconducting quantum computing and distributed quantum networks. The achieved improvements in signal clarity and measurement speed pave the way for more complex experiments and the development of scalable quantum technologies.
Tantalum Source Enables Faster Single-Photon Detection This research demonstrates a functioning microwave single-photon source created from tantalum-based thin films, establishing a promising new platform for advancements in quantum technologies.
The team successfully fabricated a device exhibiting clear single-photon characteristics, confirmed through detailed frequency, time, and correlation measurements, and importantly, the performance is comparable to existing devices built with aluminum. This achievement addresses limitations associated with earlier material choices, as tantalum offers improved thermal stability and robustness. Furthermore, the integration of a traveling-wave parametric amplifier significantly enhanced the signal-to-noise ratio in the detection process, accelerating measurement times by a factor of fifty compared to previous experiments. This improvement allows for faster and more reliable verification of the source’s single-photon statistics. The authors acknowledge that further optimization of the fabrication process and device design is needed to improve emission efficiency and coherence. 👉 More information 🗞 On-Demand Microwave Single-Photon Source Based on Tantalum Thin Film 🧠 ArXiv: https://arxiv.org/abs/2512.07589 Tags: