The second quantum revolution, a new age when we are able to manipulate the weirdness of quantum mechanics, was envisioned by the prize in physics. The holy grail of quantum information sciences is a large scale and fully functional quantum network. It will open a new world of physics with new possibilities.
Extending the distance of quantum communication is one of the biggest challenges. quantum states in superposition can't be amplified because they can't be cloned. Ultra-low-loss quantum channels and quantum memory are not enough for a high- performance quantum network. Recent progress in satellite-based quantum communications and quantum repeaters has been hampered by a lack of suitable single- photon sources.
What is required of a single photon source? The first thing it should do is emit one photon. The source should have high system efficiency and a high repetition rate. The single photon should be indistinguishable for applications that need interfering with independent photon. There are additional requirements that include a tunable platform and narrowband linewidth.
Semiconductor particles of just a few nanometers are called quantum dots. In the past two decades, the visibility of quantum interference between independent QDs has been limited to a few meters or kilometers.
An international team of researchers has achieved high-visibility quantum interference between two independent QDs. They report efficient and indistinguishable single-photon sources with low noise and high efficiency.
Single QDs are coupled to microcavities to generate single photons. The QD inhomogeneity is eliminated with the use of quantum frequencies. The visibility is high. "Feasible improvements can further extend the distance to 600 km," said the senior author.
The work jumped from the previous QD-based quantum experiments at a scale from 1 km to 300 km, two orders of magnitude larger, and thus opens an exciting prospect of solid-state quantum networks. The dawn of solid-state quantum networks is said to be near.
There is more information about quantum interference with independent single-photon sources. There is a book titled "10117/1.AP.4.6.066003."
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