Novel entangled photon source with heralding

[DrChinese]

Just saw this article from a highly respected research team, and thought some might enjoy seeing how the state of the art continues to develop rapidly:

12-photon entanglement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down-conversion
Han-Sen Zhong, Yuan Li, Wei Li, Li-Chao Peng, Zu-En Su, Yi Hu, Yu-Ming He, Xing Ding, W.-J. Zhang, Hao Li, L. Zhang, Z. Wang, L.-X. You, Xi-Lin Wang, Xiao Jiang, Li Li, Yu-Ao Chen, Nai-Le Liu, Chao-Yang Lu, Jian-Wei Pan
https://arxiv.org/abs/1810.04823

Some of the key issues in developing practical uses of entanglement in quantum communications are i) producing the entanglement on demand; or alternately ii) knowing the entanglement is coming in advance. The second is called "heralding". In the usual protocols, you don't know if you have an entangled pair coming until it arrives. In this novel experiment, which I am still trying to fully absorb, there is heralding along with the type of entanglement needed for communications. From the abstract:

Entangled photon sources with simultaneously near-unity heralding efficiency and indistinguishability are the fundamental elements for scalable photonic quantum technologies. We design and realize a degenerate entangled-photon source from an ultrafast pulsed laser pumped spontaneous parametric down-conversion (SPDC), which show simultaneously ~97% heralding efficiency and ~96% indistinguishability between independent single photons. Such a high-efficiency and frequency-uncorrelated SPDC source allows generation of the first 12-photon genuine entanglement with a state fidelity of 0.572(24). We further demonstrate a blueprint of scalable scattershot boson sampling using 12 SPDC sources and a 12*12-modes interferometer for three-, four-, and five-boson sampling, which yields count rates more than four orders of magnitudes higher than all previous SPDC experiments. Our work immediately enables high-efficiency implementations of multiplexing, scattershot boson sampling, and heralded creation of remotely entangled photons, opening up a promising pathway to scalable photonic quantum technologies.

 

[atyy]

Some of the key issues in developing practical uses of entanglement in quantum communications are i) producing the entanglement on demand; or alternately ii) knowing the entanglement is coming in advance. The second is called "heralding".

What do you think will be the uses of quantum communication?

How close are we to it?

 

[Zarqon]

What do you think will be the uses of quantum communication?

How close are we to it?

There's a very recent paper By Stephanie Wehner and others describing the updated vision for the Quantum Internet

At the start of the paper they give the following motivation for quantum communication:

"As with any radically new technology, it is hard to predict all uses of the future quantum internet. However, several major applications have already been identified, including secure communication, clock synchronization, extending the baseline of telescopes, secure identification, achieving efficient agreement on distributed data, exponential savings in communication, quantum sensor networks, as well as secure access to remote quantum computers in the cloud."

And regarding how close we are, in the roadmap/manifesto for the EU flagship on quantum technologies that is just kicking-off this month, long distance connections that require quantum repeaters should be available in the order of 5-10 years from now. Although for a full quantum internet, the best guess is still more than 10 years away.