The general requirements for applying for a PhD in physics include a bachelors degree in physics from another college or university, general GRE scores, physics GRE scores, filling in the application, letters of recommendation, and research experience. While research experience isn't explicitly required, it will definitely be expected of applicants to top PhD programs - many people applying will already have publications and research experience they can point to. And of course, a high GPA and high test scores. A PhD in physics takes an average of 6.5 years to earn, so expect between 4 and 8 years of graduate school (it depends on a lot of things, including you, your motivation, your project, and your adviser). You should be able to get a teaching or research assistantship for grad school, in which case they'll pay your tuition and pay YOU a stipend in return for teaching or doing research for them.