Entanglement Purification Rule Action

[LesterKim]

In the requirement function for entanglement purification, what is the significance of the following lines of code?

My interpretation is that memories_info[0].remote_node has two purification protocols, one that has a kept memory entangled with memories_info[0].memory and another that has a kept memory entangled with memories_info[1].memory. Those two protocols are saved in _protocols. But then, why do you set _protocols[0].meas_memo = _protocols[1].kept_memo? I don't understand the reasoning in the lines highlighted.

For context, I am wondering how to add a purification protocol that sacrifices two measured entangled pairs to purify the kept memory (e.g. single-selection double-error purification).

[xwu64]

Although I cannot open attached links, I assume the code about your questions is at here.

The logic of rules for purification protocols involves two routers to cooperate. Two routers perform different operations on the entangled memories. Let's name two routers to router A and router B here. Router A's action of rule is to select two qualified memories for the purification protocol. It's impossible to make router B perform the same action without information from router A. For example, if router A and B have three pairs of qualified memories (a1-b1, a2-b2, a3-c3) for purification, the action on router A may select a1-b1 and a2-b2 and the same action on router B may select a1-b1 and a3-b3, which prohibits cooperations of protocols for purification.

To avoid such situation, the action of router B is to create an instance of entanglement purification protocol to hold memory temporarily. Since the purification protocol only holds one memory, the protocol will not be executed. When the message from router A is received by router B, the message will notify router B which memories are selected for one purification protocol. The function "req_func" will scan these incomplete purification protocols to select incomplete protocols that hold corresponding memories. The "req_func" will use these two protocols to assemble a complete protocol to cooperate with the protocol on router A.

The referred code lines is to assemble a complete protocol. _protocols[0] denotes the protocol that holds the kept memory. _protocols[1] denotes the protocol that holds the measured memory. After the assembly, _protocols[0] is used to purify entanglement and _protocols[1] is discarded.

I know this implementation may not very eligible. I'm welcome ideas about improving the quality of code at here.

[LesterKim]

I see that the answer to my question is that the rule condition returns a list with only one memory info. Is that sufficient because the rule condition will be applied to the memory info for each memory in the node?

[xwu64]

I don't get your question. What will insufficient?

For the purification protocols that consumes multiple memories, the rule need to be designed specific for the protocol. I'm thinking moving the logic of condition and action to the class of protocols may be more reasonable. Rule manager could call functions from these entanglement protocols without knowledge about the requirement of protocols.

[LesterKim]

Since the rule condition returns a list of only one memory info, is that rule condition (and action) applied to every memory in the node during a simulation? After all, we need at least two entangled memories in the node to run purification.

[LesterKim]

I am reading chapter 4 of the tutorial again. So the rule condition is applied to all the memories in the node in a given range.

[xwu64]

Sorry for responding late. You're right the rule will check all memories to search qualified memories.