No, Switzerland is not eligible for Horizon Europe, as it has not signed the agreement with the European Union to become a third country associated to Horizon Europe. Therefore, legal entities from Switzerland cannot receive EU funding in Horizon Europe projects. There have been various rounds of negotiations and in 2021, according to the European Commission, Switzerland was about to join Horizon Europe but without success unfortunately.
Although Switzerland is not eligible for Horizon Europe, researchers in Switzerland can still participate in calls for proposals under the status, albeit to a limited extent, and receive funding directly from the Confederation. However, participation in individual projects, in particular in future calls for proposals from the European Research Council, Marie Skłodowska-Curie Actions and the European Innovation Council, is no longer possible. The Swiss Federal Council’s stated aim remains Switzerland’s full association to Horizon Europe. More information here.
The list of participating Countries in Horizon Europe is available form the European Commission website and has been published on the 15th of April 2022. According to this document, legal entities established in Switzerland are currently not covered by the transitional arrangement. It also lists all other countries eligible for Horizon Europe.
More information can be found on the website of the Swiss State Secretariat for Education, Research and Innovation.