That's incorrect. Some Jews are atheists.

"The Jewish people are an ethnoreligious group and nation originating from the Israelites, or Hebrews, of the Ancient Near East. Jewish ethnicity, nationhood and religion are strongly interrelated, as Judaism is the traditional faith of the Jewish nation, while its observance varies from strict observance to complete nonobservance." - Wikipedia

"Jewish" describes a diverse group of people that transcends their traditional religion. You can't use the term Jewish in the way that we use the terms Muslim or Christian. Muslims and Christians are identified by their adherence to their respective religions, regardless of their ethnicity. Jews may or may not identify with Judaism, but they're still Jews.