Add support for nodes with more than 3 qubits

[brunorijsman]

Add support for nodes with more than 3 qubits

The constructor for NetQASMConnection has a max_qubits parameter.

In my application (QFT) I need more than 3 qubits per node.

When I construct a NetQASMConnection with a value of greater than 3, I don't get any exception: the constructor succeeds.

However, later in the run, when I actually try to allocate the qubits, I get exception RuntimeError("No more qubits left in qdevice")

The root cause for this is that QNE-ADK has a hard-coded topology adk/networks/nodes.json which hard-codes the number of qubits per node to 3 qubits:

{
  "nodes": [
    {
      "name": "Amsterdam",
      "slug": "amsterdam",
      "coordinates": {
        "latitude": 52.3667,
        "longitude": 4.8945
      },
      "node_parameters": [
        "gate-fidelity"
      ],
      "number_of_qubits": 3,     <<<
      "qubit_parameters": [
        "relaxation-time",
        "dephasing-time"
      ]
    },
    ...

If I manually edit the QNE-ADK nodes.json file and increase number_of_qubits from 3 to 32, my QFT application runs fine (I don't get RuntimeError("No more qubits left in qdevice") anymore)

Requested feature:

• Let users define their own topology (i.e. their own nodes.json file), or

• Let users choose their own number of qubits per node, or

• Increase the hard-coded value of number_of_qubits in QNE-ADK.

Note 1: In my environment I created a script to automatically "fix" the nodes.json file (https://github.com/brunorijsman/quantum-internet-hackathon-2022/blob/main/qne_adk/fix_qne_adk_number_of_qubits.py)

Note 2: I realize that the hardware for the real quantum network which is being constructed in the Netherlands may not support more than 3 qubits per node, but the simulator seems to support it just fine (at least, running locally)