NVIDIA / NVIDIA/cuda-quantum

Draw functionality unclear for state preparation

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Dominant language
C++
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Description

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Describe the bug

kernel_2 below is a 2q kernel, sample returns a 2q result however draw plots a 1q circuit.


import cudaq 

@cudaq.kernel 
def kernel_1():
    q = cudaq.qvector(1)
    x(q)

state = cudaq.get_state(kernel_1)


@cudaq.kernel
def kernel_2(state: cudaq.State):
    
    a = cudaq.qvector(1)
    b = cudaq.qvector(state)
    
    x(a)

print(cudaq.draw(kernel_2, state))
print(cudaq.sample(kernel_2, state))


     ╭───╮
q0 : ┤ x ├
     ╰───╯

{ 11:1000 }

Steps to reproduce the bug

NA

Expected behavior

NA

Is this a regression? If it is, put the last known working version (or commit) here.

Not a regression

Environment
  • CUDA-Q version:
  • Python version:
  • C++ compiler:
  • Operating system:
Suggestions

No response

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the provided Python snippet using cudaq.draw(kernel_2, state) and cudaq.sample(kernel_2, state). Trace the draw entry point and its handling of a cudaq.State, then compare the qubit count with the sample result. Done means the issue's state-preparation behavior is understood and the drawn circuit correctly reflects the state input, or the limitation is documented.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
quantum-computing
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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