Researchers at Nanjing University achieve a breakthrough in quantum storage, bringing us closer to large-scale quantum networks
Quantum technologies are rapidly advancing, offering the potential for revolutionary advancements in computing and communication. However, to fully realize the power of quantum devices, they must be interconnected in networks. While classical devices can rely on existing fiber-optic networks, the storage of quantum information at the frequencies used in telecom networks has remained a challenge. In a groundbreaking study published in Nature Communications, researchers at Nanjing University have achieved record-long quantum storage at telecom wavelengths, providing a crucial step towards practical large-scale quantum networks.
The Challenge of Quantum Signal Regeneration
The optical signals used in classical telecommunications networks require periodic signal amplification to compensate for losses over long distances. However, conventional methods of signal amplification are not suitable for quantum states of light due to the loss of quantum correlations. Quantum repeaters offer a solution by storing and transforming entangled states to maintain quantum correlations. The key to quantum repeaters is the development of quantum memories that can store quantum states of light for extended periods.
Extending Storage Time at Telecom Wavelengths
Storing quantum states of light at telecom wavelengths, around 1.5 µm, has been a significant challenge. The research team at Nanjing University, led by Prof. Xiao-Song Ma, has developed quantum memories based on yttrium orthosilicate crystals doped with erbium ions. Erbium ions have ideal optical properties for use in existing fiber networks, making them a promising choice for quantum storage. Previous implementations of erbium-ion-based quantum memories have been relatively inefficient, but the team at Nanjing University has made significant advances in perfecting the techniques.
A Decisive Step Towards Practical Devices
The team at Nanjing University achieved a storage time of close to two microseconds for the entangled state of two telecom photons, which is nearly 400 times longer than previous demonstrations in this field. This breakthrough brings us closer to practical quantum repeaters and large-scale quantum networks. The researchers were able to preserve the entanglement of the photon pair even after storing them for 1936 nanoseconds, allowing for manipulation of the quantum state during storage. Additionally, they combined their quantum memory with a novel source of entangled photons on an integrated chip, further enhancing the potential for low-cost mass production.
The Promise of a Quantum Internet
The ability to generate high-quality entangled photons at telecom frequencies and store the entangled state on a solid-state platform is a significant achievement. This breakthrough establishes a promising building block that can be integrated into existing large-scale fiber networks, paving the way for a future quantum internet. A quantum internet would enable secure communication, enhanced computational power, and a wide range of applications that go beyond the capabilities of classical technologies.
Conclusion:
The achievement of record-long quantum storage at telecom wavelengths by the researchers at Nanjing University is a significant milestone in the development of practical quantum networks. By extending the storage time of entangled photons and combining it with a solid-state platform suitable for mass production, the team has overcome key challenges in quantum repeater technology. This breakthrough brings us closer to realizing the full potential of quantum technologies and opens up new possibilities for secure communication and advanced computing. As quantum technologies continue to mature, the path towards a quantum internet becomes clearer, promising a future of unparalleled capabilities.
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