Quantum dot device provides single photons, a building block for future communication networks
Quantum dot device provides single photons, a building block for future communication networks lead image
Quantum key distribution (QKD), a secure communication method based on the fundamentals of quantum mechanics, depends on the development of sources of single photons.
Gao et al. demonstrated a QKD testbed using a quantum dot single-photon source. The quantum dot acts as an artificial atom, generating a single photon after a laser trigger.
“Single photons are very interesting when it comes to exchanging quantum information because photons, especially in optical telecom fibers, can be transmitted very well,” said author Lucas Rickert.
Single photons are generally difficult to obtain but important for security purposes. Dimmed laser sources have been used in the past, but they emit multiple photons according to a Poisson distribution.
“With quantum dot systems as real single-photon sources, you can achieve a probability to have a single photon per excitation which is close to unity,” said author Timm Gao. “In a laser system, the best you can get is a 37 percent chance.”
The team used a plug & play single-photon source that is cooled to 40 K with a compact Stirling cryocooler, avoiding the previously required large liquid helium infrastructure. It is permanently fiber-coupled, making realignment unnecessary.
The benchtop source operates at the telecom O-band, which has low fiber losses ideal for urban scale networks. The source was evaluated in a QKD testbed to assess its performance for use in future quantum communication infrastructure.
The researchers aim to improve the device with a better underlying structure and to realize other types of quantum-secured information exchange protocols with such compact systems. Further afield, they hope to cool the photon source to lower temperatures so photons will be indistinguishable.
Source: “A quantum key distribution testbed using a plug&play telecom-wavelength single-photon source,” by Timm Gao, Lucas Rickert, Felix Urban, Jan Große, Nicole Srocka, Sven Rodt, Anna Musiał, Kinga Żołnacz, Paweł Mergo, Kamil Dybka, Wacław Urbańczyk, Grzegorz Sęk, Sven Burger, Stephan Reitzenstein, and Tobias Heindel, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0070966 .
