[RFC] Python frontend for 'photonics' target

[khalatepradnya]

Required prerequisites

• [X] Search the issue tracker to check if your feature has already been mentioned or rejected in other issues.

Describe the feature

• Add support to use the photonics target from Python frontend of CUDA-Q

• Proposed API

  • Gates (same as those supported on C++ frontend):

    1. plus(q: qudit) -> None,
    2. phase_shift(q: qudit, phi: float) -> None,
    3. beam_splitter(q: qudit, r: qudit, theta: float) -> None,
    4. mz(q: qudit) -> int and mz(q: list[qudit]) -> list[int]

  * A decorator for photonics kernel which defines the qudit level for all qudits within the kernel (Defaults to level = 2, i.e., qubit): @cudaq.photonics_kernel(level=N) * A photonics kernel is defined with @cudaq.kernel(handler="orca")

  • Handler is inferred from the target
  • Custom handler must provide API for defining a qudit of level = N, for example, qudit(3)
  • API for sampling: cudaq.sample(kernel)

• Example

  
  import cudaq

cudaq.set_target("photonics")

@cudaq.kernel def photonicsKernel():
qutrits = [qudit(3) for i in range(2)] plus(qutrits[0]) plus(qutrits[1]) plus(qutrits[1]) mz(qutrits)

counts = cudaq.sample(photonicsKernel) print(counts)

[khalatepradnya]

For vis, @Omar-ORCA

[Omar-ORCA]

For vis, @Omar-ORCA

LGTM

[khalatepradnya]

Updated the decorator as per inputs from @amccaskey

[bettinaheim]

Let's have a quick sync on implementation to make sure we are not missing anything that will lead to some technical pain across the different scenarios in the future. We'll set something up for a larger group and once we have confirmation that works across the board, we can approve and move forward with it. Acknowledged that the API looks good - not we need to talk implementation. :)

[khalatepradnya]

API docs