Researchers from Tokyo University of Science, including Associate Professor Kaoru Sanaka, Associate Professor Mark Sadgrove, and Mr. Kaito Shimizu, along with Professor Kae Nemoto from the Okinawa Institute of Science and Technology Graduate University, have developed a single photon light source using ytterbium-doped optical fibers. This technology, which operates at room temperature, could make quantum networks more cost-effective and accessible. Ytterbium, a rare-earth element, is ideal for this application due to its favourable optical and electronic properties. The team’s findings, published in the journal Physical Review Applied, could have implications for quantum communication, random number generation, and high-resolution image analysis. The latest results are published in PHYSICAL REVIEW APPLIED.
Quantum Technologies: The Role of Ytterbium-Doped Optical Fibers in Creating a Single Photon Source
Quantum-based systems, which promise faster computing and stronger encryption for computation and communication systems, can be built on fiber networks. These networks involve interconnected nodes consisting of qubits and single-photon generators that create entangled photon pairs. Rare-earth (RE) atoms and ions in solid-state materials are particularly promising as single-photon generators. These materials are compatible with fiber networks and emit photons across a broad range of wavelengths.
Optical fibers doped with these RE elements could be used in various applications, such as free-space telecommunication, fiber-based telecommunications, quantum random number generation, and high-resolution image analysis. However, the development of single-photon light sources has so far been limited to RE-doped crystalline materials at cryogenic temperatures, which restricts the practical applications of quantum networks.
Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a silvery-white metal that is reasonably stable in air, and it belongs to the lanthanide series, commonly known as rare earth elements, on the periodic table. Ytterbium has several isotopes, and naturally occurring ytterbium is composed of seven stable isotopes.
Breakthrough in Quantum Networks: Room Temperature Single Photon Light Source
A team of researchers from Japan, led by Associate Professor Kaoru Sanaka from Tokyo University of Science (TUS), has successfully developed a single photon light source consisting of doped ytterbium ions (Yb3+) in an amorphous silica optical fiber at room temperature. This development eliminates the need for expensive cooling systems, potentially making quantum networks more cost-effective and accessible.
Single photon light sources are devices that control the statistical properties of photons, the smallest energy units of light. The team developed a single-photon light source using an optical fiber material doped with optically active RE elements. The experiments revealed that such a source can be generated directly from an optical fiber at room temperature.
Ytterbium: A Suitable Candidate for Doping the Fiber
Ytterbium, an RE element, has favourable optical and electronic properties, making it a suitable candidate for doping the fiber. It has a simple energy-level structure, and ytterbium ion in its excited state has a long fluorescence lifetime of around one millisecond.
To fabricate the ytterbium-doped optical fiber, the researchers tapered a commercially available ytterbium-doped fiber using a heat-and-pull technique, where a section of the fiber is heated and then pulled with tension to gradually reduce its diameter.
The Role of Rare-Earth Atoms in Defining Fiber’s Optical Properties
Within the tapered fiber, individual RE atoms emit photons when excited with a laser. The separation between these RE atoms plays a crucial role in defining the fiber’s optical properties. If the average separation between the individual RE atoms exceeds the optical diffraction limit, which is determined by the wavelength of the emitted photons, the emitted light from these atoms appears as though it is coming from clusters rather than distinct individual sources.
To confirm the nature of these emitted photons, the researchers used an analytical method known as autocorrelation, which assesses the similarity between a signal and its delayed version. By analyzing the emitted photon pattern using autocorrelation, the researchers observed non-resonant emissions and further obtained evidence of photon emission from the single ytterbium ion in the doped filter.
The Future of Quantum Information Technologies
While the quality and quantity of emitted photons can be enhanced further, the developed optical fiber with ytterbium atoms can be manufactured without the need for expensive cooling systems. This overcomes a significant hurdle and opens doors to various next-generation quantum information technologies.
The team has demonstrated a low-cost single-photon light source with selectable wavelength and without the need for a cooling system. Going ahead, it can enable various next-generation quantum information technologies such as true random number generators, quantum communication, quantum logic operations, and high-resolution image analysis beyond the diffraction limit.
“Single-photon light sources are devices that control the statistical properties of photons, which represent the smallest energy units of light,” “In this study, we have developed a single-photon light source using an optical fiber material doped with optically active RE elements. Our experiments also reveal that such a source can be generated directly from an optical fiber at room temperature.”
Dr. Sanaka.
“We have demonstrated a low-cost single-photon light source with selectable wavelength and without the need for a cooling system. Going ahead, it can enable various next-generation quantum information technologies such as true random number generators, quantum communication, quantum logic operations, and high-resolution image analysis beyond the diffraction limit,”
Dr. Sanaka.
Summary
Researchers from Japan have developed a single-photon light source using ytterbium-doped optical fibres, which can operate at room temperature, potentially making quantum networks more cost-effective and accessible. This development could enable various next-generation quantum information technologies such as faster computing, stronger encryption, quantum communication, and high-resolution image analysis.
- A team of researchers from Japan, led by Associate Professor Kaoru Sanaka from Tokyo University of Science (TUS), has developed a single-photon light source using ytterbium-doped optical fibers.
- Other team members include Associate Professor Mark Sadgrove, Mr. Kaito Shimizu from TUS, and Professor Kae Nemoto from the Okinawa Institute of Science and Technology Graduate University.
- This development could make quantum networks more cost-effective and accessible, as it eliminates the need for expensive cooling systems.
- Quantum-based systems, which promise faster computing and stronger encryption, can be built on fiber networks involving interconnected nodes consisting of qubits and single-photon generators.
- The ytterbium-doped optical fiber was created using a heat-and-pull technique on a commercially available ytterbium-doped fiber.
- The researchers used an analytical method called autocorrelation to confirm the nature of the photons emitted from the ytterbium ions in the doped fiber.
- This development could enable various next-generation quantum information technologies such as true random number generators, quantum communication, quantum logic operations, and high-resolution image analysis beyond the diffraction limit.