Qiskit "statevector_gpu" method not available

Question

I am trying to use the statevector_gpu simulation method in Qiskit Aer (see this page). I installed qiskit-aer-gpu according to the instructions on this page. It was working last week and then stopped working. I'm not sure what changed. (It's a shared computer.) I get the error message qiskit.providers.aer.aererror.AerError: "Invalid simulation method statevector_gpu. Available methods are: ['automatic', 'statevector']".

Thanks in advance for the help!

Here is the relevant system information:

• It is a shared computer running Ubuntu 18.04.4 LTS.
• I have qiskit 0.23.0, qiskit-aer 0.7.0, qiskit-aer-gpu 0.7.0 installed in an environment in conda 4.8.5 with python 3.8.5.
• nvcc --version gives Cuda compilation tools, release 10.0, V10.0.130
• nvidia-smi shows 4 GPUs available and indicates CUDA Version: 10.2.

Answer 1

The qiskit-aer and qiskit-aer-gpu are mutually exclusive packages. They contain the same code except that the qiskit-aer-gpu package built with CUDA support enabled. If you install both packages at the same time the contents of the 2 packages will interfere with each other. I would recommend creating a new conda environment and installing qiskit-terra and qiskit-aer-gpu manually with pip install -U qiskit-terra qiskit-aer-gpu (and add qiskit-ignis, qiskit-aqua, and qiskit-ibmq-provider if they're needed). If you still have issues with only qiskit-aer-gpu installed in the environment please file an issue at https://github.com/Qiskit/qiskit-aer/issues and we can work on debugging it there.