Designing Quantum Repeater Networks

# About publication
Authors: Rodney Van Meter and Joe Touch
Magazine: IEEE Communication Magazine
Data: August 2013
[Paper Link](http://aqua.sfc.wide.ad.jp/publications/van-meter-ieee-communications_Aug_2013.pdf)

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# Motivation
Let's design the alternative Internet using the quantum computer technology

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<img src="http://www.clipartkid.com/images/264/internet-cloud-clip-art-at-clker-com-vector-clip-art-online-royalty-sTEbDg-clipart.png" width="200" height="100"/>
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<img src="https://previews.123rf.com/images/martialred/martialred1605/martialred160500007/56301196-Quantum-computer-chip-flat-icon-for-apps-and-websites-Stock-Vector.jpg" width="200" height="100"/>
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# What to Learn from this paper
Q1. Can we construct the Internet with the quantum computer technology?
Q2. How can we build the distributed quantum network?
Q3. What is the difference (restrictions) between the classic and the quantum network?

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# Q1. Can we construct the Internet with the quantum computer technology?
A1. Yes, but the quantum network is not equivalent to the classic network.

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# Q2. How can we build the distributed quantum network?
Prerequisite Knowledge
1. the classic network architecture
2. basic knowledge about quantum computing

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# 1. the classic network architecture
![classic TCPIP layers.jpg](https://qiita-image-store.s3.amazonaws.com/0/142884/3db0314b-1532-84ee-52f2-ad2b00499867.jpeg)

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# 2. basic knowledge about quantum computing
a. Qubit
b. EPR pair
c. Teleportation
d. Purify and Swap (proposed Quantum Error Correction mechasnim)

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# a. Qubit
- The unit of quantum information
- Unlike classic bit, a qubit has three states; 0, 1 and superposition
- A qubit has globally unique but limited number of patterns
- You can measure the patterns of quantum state with 100% probability
- No clone

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# b. EPR pair
- group of qubits exhibiting strong correlation between two qubits

![Qubit Overivew.jpg](https://qiita-image-store.s3.amazonaws.com/0/142884/03c4e9d3-cf1f-bb84-1eeb-c5eff0467b44.jpeg)

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# c. Teleportation
- an idea to transfer a qubit
   - e.g., send 1001 from A to B
![Qubit Overivew.jpg](https://qiita-image-store.s3.amazonaws.com/0/142884/03c4e9d3-cf1f-bb84-1eeb-c5eff0467b44.jpeg)

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# d. Purify and Swap 
- proposed Quantum Error Correction mechasnim
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step1: find the EPR pair
step2: measure patterns of a qubit
step3: swap a qubit
step4: agree to begin quantum communication

![Purify & Swap.jpg](https://qiita-image-store.s3.amazonaws.com/0/142884/04f46720-c2f8-e808-0d90-aa2e949d86d5.jpeg)


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# Q2. What is the design of the quantum network?
A2. QRNA (Quantum Recursive Network Architecture)
- vertical network architecture for protocol stacks
- horizontal network architecture for application design

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# Vertical QRNA
![QRNA model.jpg](https://qiita-image-store.s3.amazonaws.com/0/142884/54a72a64-0d5a-5580-dee6-ba13735f9a6e.jpeg)

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# Horizontal QRNA
![fig4.png](https://qiita-image-store.s3.amazonaws.com/0/142884/0f451e6c-d583-dd97-1a7c-8d0cf717c73a.png)

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# Q3. What is the difference between the classic and quantum network?
<img src="https://qiita-image-store.s3.amazonaws.com/0/142884/599d2e17-6242-6a18-6152-73ce2542bef4.png" height="300"/>

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# Conclusion
- QRNA is the proposed concept of the distributed quantum network
- future work: engineering the network