EU/EEA and Swiss citizens
You do not need a work permit or visa.
If you are a scientist invited to a scientific establishment in Sweden for the purposes of teaching or lecturing only, and for a period of less than three months, you do not need a work permit. However, nationals of some countries will need a visa (see our Visa page).
If you are a researcher (post-PhD) hired to work in Sweden for any period of time, you need to get a work permit entered into your passport before you arrive in Sweden. In many cases, you can begin your application for a work permit online. Otherwise, you apply at a Swedish embassy or consulate near you.
The Swedish Migration Board's website has full instructions.