Title: What are quantum repeaters?
Type: Webpage
Source: https://www.aliroquantum.com/blog/what-are-quantum-repeaters
Quantum repeaters are the key to unlocking ability to transmit qubits over long distances, for a global quantum internet.
Ideas in classical repeaters can't be used in quantum repeaters:
- no-cloning theorem
- measurement of quantum states destroys them
- photons transmitted through fiber optic cables suffer from attenuation
Core idea is based on the idea of entanglement swapping. The primary goal of quantum networks is to distribute entanglement between members of the network.
Entanglement swapping uses teleportation to create long distance communication links from a chain of locally connected repeaters. Long distance entanglement is achieved from several short-distance entanglements.
First repeaters need to be designed to handle limitations of current devices.
Types of errors:
- Loss errors
- Operation errors
Approaches to handle errors:
- Heralded Entanglement Generation (HEG)
- Heralded Entanglement Purification (HEP)
- Quantum Error Correction (QEC)
They represent imporvements in quantum networks with increasingly powerful applications as technology improves.
Apply entanglement distillation to handle errors - basically, one can get a high fidelity entanglement from many copies of low fidelity entanglement. Communication rate in such a network is limited by distillation process.
Rely on quantum error correction to handle operation errors. Network handles much higher speeds.
Improved quantum devices means quantum error correction will be used to handle both operation and loss errors. Much higher rate of communication.
- https://www.nature.com/articles/nature11472?page=4#citeas -
Ma, XS., Herbst, T., Scheidl, T. et al. Quantum teleportation over 143 kilometres using active feed-forward. Nature 489, 269–273 (2012). https://doi.org/10.1038/nature11472 - https://www.nature.com/articles/s41566-019-0468-5 -
Li, ZD., Zhang, R., Yin, XF. et al. Experimental quantum repeater without quantum memory. Nat. Photonics 13, 644–648 (2019). https://doi.org/10.1038/s41566-019-0468-5 - https://www.nature.com/articles/srep20463 -
Muralidharan, S. et al. Optimal architectures for long distance quantum communication. Sci. Rep. 6, 20463; doi: 10.1038/srep20463 (2016). - https://inqnet.caltech.edu/PRX-Brief.html -
On high fidelity quantum teleportation for practical quantum networks