Implement an example of a second generation quantum repeater

[stephendiadamo]

A first generation quantum repeater uses entanglement swapping to establish quantum entanglement between two parties not directly connected.

A second generation quantum repeater uses heralded quantum entanglement and error correction. One can read more about them here: https://arxiv.org/abs/1509.08435

In this example, we should implement a second generation quantum repeater.

[SakibulIslamSazzad]

I would love to work on this project, it looks interesting.

[SakibulIslamSazzad]

Hi @ stephendiadamo I did some ground study for the project, I have some asks that I would like to proceed:

1. I found that entanglement distillation is necessary for 2G quantum repeaters to reduce the loss errors, what should be my approach to make a circuit block of entanglement distillation- will be for two qubit states/ general n qubit states?
2. I think there is difference between entanglement distillation and entanglement purification, my understanding says that for 2G entanglement distillation is discussed everywhere, so would distillation be enough for 2G?

[SakibulIslamSazzad]

One another thing, should I do the entanglement distillation for pure states or mixed states?

[stephendiadamo]

In general this issue is pretty open-ended. I'm not an expert in quantum repeaters but just thought a very high-level example of doing perhaps one round of distillation to establish entanglement between nodes could be nice to see. A lot of the implementation choices are left to you since I wouldn't know how to complete this issue without more research myself.

In QuNetSim, we are dealing just with pure states but one can apply errors on qubits like an X error or a Z error which can be corrected in the protocol.

Maybe the first thing to start with is better understanding distillation and writing a protocol that only does that part.

In QuNetSim, one has to apply the logic gates directly on the qubits one at a time, so you'll have to write some sort of algorithm that takes qubits and applies the correct gates on them to perform circuits.

I'll try to read up a bit more and hopefully can be more helpful.

[SakibulIslamSazzad]

Great, I am studying entanglement distillation from Nielsen and Chuang Book

[pritamsinha2304]

@stephendiadamo Anyone working on this project ?

[stephendiadamo]

@SakibulIslamSazzad How's your status with this? Are you still planning to work on it?

[SakibulIslamSazzad]

@stephendiadamo hey yeah I am working on it. But my progress is slow, may be I wont do it for unitary hack. It seems like quite a good project and I was busy with IBM Challenge 2021. @pritamsinha2304 if you are interested can go ahead. I can share my resources and understanding with you.

[pritamsinha2304]

I was also participating in IBM challenge that's why I couldn't focus on unitary hack. So I am thinking is this doable in 3 days. I mean I am learning this concept right now, but @SakibulIslamSazzad you were on this project from the beginning. Why don't you start ? And I will contribute to it. If you started already, how far are you ?

[SakibulIslamSazzad]

I am not sure if this doable within 3 days. I can give a bit summary what the project is about. Basically you have to generate 2nd generation quantum repeaters (QR). But the key thing is that the 2nd generation QR has 2 specific properties: Heralded Entanglement Generation (HER) this is Loss error and other one is Quantum Error Correction (QEC) for operational loss. I have some ground study and understanding about QEC (even IBM challenge has a problem statement on it). So I am quite struggling how can I merge QEC with HER. I think if you are interested we can team up. Here is my linkedin profile: []

Lets talk there more.

[pritamsinha2304]

@SakibulIslamSazzad I can't message you

[SakibulIslamSazzad]

well, you can send me an invitation. or email me at: sakibulislamsazzad@gmail.com

[pritamsinha2304]

@stephendiadamo I have 2 questions/confusions:

1. I see the 1st generation repeater create entanglement between 2 parties. Does send_epr() is based on this or I am wrong ?
2. In this repeater, there are intermediate stations. Can we and should we consider intermediate nodes as the station like eve.

[SakibulIslamSazzad]

I think I can answer the second question: Intermediate nodes aren't eavesdropper, the nodes are two point that split the whole network length, In the QR these nodes are for generating high fidelity entanglement states.