Researchers have successfully transmitted, stored, and retrieved quantum data through standard fiber optic cables, marking a significant advancement toward the quantum internet. This breakthrough, detailed in a study by scientists from Imperial College London, the University of Southampton, and the Universities of Stuttgart and Wurzburg, was published on April 12 in the journal Scientific Advances.
Currently, quantum information is unstable over long distances. Quantum bits, or qubits, which carry this information, often get lost or fragmented during transmission. While classical computer bits are sent as light pulses through fiber optic cables with the help of repeaters, qubits require similar devices to maintain signal integrity over long distances.
These new quantum memory devices can receive, store, and retransmit qubit states. The research team demonstrated this capability using standard fiber optic cables, which is a significant step forward.Photon Source Innovation
The researchers used a new method to store and retrieve photons, the potential carriers of quantum information. According to Sarah Thomas, a physics professor at Imperial College London, there are two main types of single photon sources: non-linear optical frequency conversion and single emitters like quantum dots. Quantum dots, which are nanocrystals of semiconductors, produce photons at a higher rate than non-linear optics, making them more reliable for quantum memory.
The efficiency of quantum memory devices depends on matching the wavelength and bandwidth. The study overcame previous inefficiencies by using a high-bandwidth, low-noise quantum memory and fabricating the photon source at a specific wavelength to match the quantum memory. This was done at a wavelength with minimal loss in optical fiber, crucial for future quantum networks.
Building on Previous Advances
This study builds on prior advancements, such as a breakthrough at Stony Brook University, which achieved a stable quantum network connection at room temperature. While the Stony Brook study demonstrated photon interference after storage and retrieval at 795 nm, the Imperial study stored and retrieved photons at 1529 nm, the standard telecom wavelength, crucial for low-loss fiber transmission.
Mark Saffman, chief scientist for quantum information at Infleqtion, and cybersecurity expert Michael Hasse highlighted the complementary nature of these studies. The Imperial study focuses on long-distance communication using repeaters, while the Stony Brook study addresses the room temperature storage of quantum information, both essential for developing cost-effective quantum networks.
