Bug#1098454: python3-qutip: Importing 'qutip.qip' requires new Debian 'python3-qutip-qip' package.

[Dirk Lehmann]

Package: python3-qutip
Version: 5.0.3-1+b3
Severity: normal

Dear Maintainer,

If I run the following file with `python3`

  * https://github.com/YouDirk/quantum_examples/blob/5f016a0f1533b7540ecd1c1ab6c00112e4c43bc8/qutip/000_sim-circ-bellstate.py

then I get the following error output

```
./000_sim-circ-bellstate.py 
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/qutip/qip.py", line 5, in <module>
    import qutip_qip
ModuleNotFoundError: No module named 'qutip_qip'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/dirk/myfiles/quantum_examples/qutip/./000_sim-circ-bellstate.py", line 26, in <module>
    import qutip.qip.circuit as cc
  File "/usr/lib/python3/dist-packages/qutip/qip.py", line 9, in <module>
    raise ImportError(
    ...<3 lines>...
    )
ImportError: Importing 'qutip.qip' requires the 'qutip_qip' package. Install it with `pip install qutip-qip` (for more details, go to https://qutip-qip.readthedocs.io/).
```

The raising error in /usr/lib/python3/dist-packages/qutip/qip.py is
distributed in the Debian package `python3-qutip` here.  I found out
that

  * since QuTiP version 5.0.0 `qutip.qip` is an optional PIP-package
    https://github.com/qutip/qutip/discussions/1500

The source of the new QuTiP-QIP package you can find here

  * https://github.com/qutip/qutip-qip

----------------------------------------------------------------------

POSSIBLE SOLUTION
*****************

For my point of view there is a

  * new Debian package `python3-qutip-qip`

required which is recommended (or depending on) by `python3-qutip`.

Can anyone here maintain such a new package?

Greets, Dirk Lehmann

----------------------------------------------------------------------


-- System Information:
Debian Release: trixie/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 6.12.12-amd64 (SMP w/20 CPU threads; PREEMPT)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages python3-qutip depends on:
ii  g++                                 4:14.2.0-1
ii  libc6                               2.40-6
ii  libgcc-s1                           14.2.0-16
ii  libstdc++6                          14.2.0-16
ii  python3                             3.13.1-2
ii  python3-dev                         3.13.1-2
ii  python3-matplotlib                  3.8.3-3+b3
ii  python3-numpy [python3-numpy-abi9]  1:1.26.4+ds-13
ii  python3-packaging                   24.2-1
ii  python3-scipy                       1.14.1-4

python3-qutip recommends no packages.

Versions of packages python3-qutip suggests:
ii  python-qutip-doc  5.0.3-1

-- no debconf information