I can add my experience. I'm not an experimentalist but I'm just about done my PhD now and started working at a company.
Indeed internships will be the best route to getting more industry related experience, which will help later if you apply to other companies. Doing an internship also networks you with that same company, and it could also be they hire you full time after your PhD which is very common.
Apart from internships, publishing papers acts as a portfolio, so having high quality, relevant, publications will make it easier for you when applying to companies working in similar domains. I think given you already know you want to work at at a company, it would make sense to have your thesis be a collection of publications instead of one big project. This will allow for flexibility in terms of orienting your work towards a particular company.
Of course networking in the quantum community is also a major source of finding out about jobs and also for knowing people who work at different companies. I found conferences weren't so great (could be due to the current virtualization) for networking, but the kind of communities that are voluntary and had community were best and more active. I think don't be scared to join meetings you may not be able to contribute to right away. It'll help see what people are working on and meeting people whose work you find interesting.
Overall, the quantum community is not so big, I think any way you approach it will allow for many opportunities.