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QTM3x / Quantum-Internet

In this repository, we will collaborate on building the quantum internet and developing applications for it.
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Need literature on attempts to implement the transport and network layers #3

Open QTM3x opened 4 years ago

QTM3x commented 4 years ago

We already know of a proposed protocol for the link layer (links in the readme inside the Link Layer folder). What about the two layers above it?

adityakrgupta25 commented 4 years ago

Hi, I would like to work on this issue but have trouble figuring out where to start from. Can you give some pointers?

BassemSafieldeen commented 4 years ago

Hi @adityakrgupta25 ,

Recall that the purpose of the link layer to create entanglement between two adjacent quantum internet nodes. So if we have a node A and a node B, the link layer is responsible for helping A and B each end up with one half of an entangled pair. This is no trivial job: the link layer has to fight things like lossy optical fibers between A and B, low efficiency photon detectors at A and B, and other problems that might mess up the creation of entanglement. But this is the link layer's job so let's let link layer worry about all that, and let's focus instead on the transport and network layers.

The purpose of transport and network layers is to make sure entanglement can be created between two quantum internet nodes that are not adjacent --- let's a call them nodes A and C. We cannot create entanglement between A and C by sending the two halves of the entangled state directly to A and C, because the distance between them is too great and the photons are going to get lost in the fibers for sure. What we are going to do instead is the following: first, we are going to ask the link layer to make entanglement between A and B, and between B and C; this gives us 

                                             A <-> B <-> C.

Then, we are going to do something called entanglement swapping inside the node B, which finally gives us what we need: 

                                               - - - - - - - -
                                     A <- /          B        \ -> C.

Now, like with the link layer, this is not as simple as it sounds. The entangled pair between A and B and B and C do not arrive at B at the same time; i.e., First we could have A <-> B C, then A <-> B <-> C. So while waiting for the link layer to create entanglement between B and C, the nodes A and B need to keep the entanglement they have alive, by storing their entangled qubits in quantum memories. But quantum memories are very delicate and have short lives! So may be by the time the entanglement between B and C is created the entanglement between A and B is no longer in the memory. It's stuff like that that calls for a sophisticated transport and network layers, see?

It would be great if you could help us review the literature on current proposals for how the transport and network layers could be implemented! If you have understood what I have written above, you should have no problem following section 6 of this nice paper. I would recommend following the papers cited in section 6 and bring the things you learn into this repository; you can even just quote from the papers the things you think are relevant. I suggest you begin with references [37] and [69].

Let me know if you need any help with this.

adityakrgupta25 commented 4 years ago

Apologies for replying late. Have gone through the base paper. Will be catching up on the references in the upcoming week.

holaditya commented 4 years ago

Hi, this my personal account for @adityakrgupta25 . I was wondering if I should go in depth about the mathematics of quantum error detection codes, checksum or should we just provide a brief overview.

BassemSafieldeen commented 4 years ago

Well, the current milestone we are trying to achieve is to do BB84 QKD. We will need a transport layer because we are assuming the two parties are separated by 100 km. There are different transport layer proposals and they do quantum error correction in different ways; each of them works under certain circumstances. So I would say let us aim for a brief overview of the different proposals before going in depth into any of them. This is from a practical standpoint.

From a fun-oriented standpoint, if you are curious about the details of how quantum error detection is performed then definitely go for it!