Visa for Non-EU Citizen
Since travel rules and recommendations are kind of fluid lately our recommendation is to get the information from the horses mouth ie. the Swedish migration agency. Also if you are visiting or joining a big organisation like MAX IV, LU, ESS or a bigger company in the area they often have staff and experience supporting you before and during your trip to Sweden.
For EU citizen (actually EEA) there are basically no restrictions for travelling to Sweden for 89 days. And if you work, study or have sufficient means to support yourself, you automatically have right of residence in Sweden. If you are a family member of an EU/EEA citizen who has right of residence, you, too, have right of residence (Swedish Migration Agency). Life in Sweden in the long term will be MUCH easier with a personal identity number, you’ll get one here: Swedish Tax Agency.