What is the Minimum GPA for admission in a graduate school in a respectable science university in the US?
(In the US) in Physics, some programs will weight things like the physics subject GRE and research experience, especially publications, ahead of the GPA. However, some schools do have a GPA cut-off around 3.0, so it's possible some schools wouldn't get far enough into your application to read it. 

If you want to apply to prestigious or highly-selective programs right now, I think you would need: 


To have scored very well on the general and physics-subject GREs.
Very good letters of recommendation that speak directly to your ability to succeed in a graduate program. 
An "explanation" for your GPA in your application. Was it because you worked a lot? Was it because you spent a lot of time doing research? Do your last couple semesters show a better GPA than your overall GPA? If so, you could make an argument that you addressed the issues that led to your lower GPA during the course of your undergraduate career, and these issues will not continue to impact your graduate performance. 


If you don't fee you have documented supplementary support like that, you still have options:

Take a year off and gain experience
You can also take a year or two off and work a research/physics-related job or internship, and/or take a couple extra classes. Taking one class at a time while working a job or internship can push up your overall GPA that they will consider (and can go a long way to making your graduate career easier), and if you spend a year or so doing something else, there will be more focus on what else you were doing. If you can get a publication during that time, that's an excellent way to display that you do have the skills to succeed in a graduate program.

Apply to "Bridge" programs
Several universities have Bridge programs, meant to help students build a competitive background for graduate study. Often, these Bridge programs also grant your access to that institution's graduate program, if you finish 1-2 years of the bridge program in good standing. One example is The University of Chicago's Physics Bridge program. This is not a masters.

Apply to Masters programs
Many universities have Masters programs, which may include the opportunity of transferring into the university's graduate program, or to another university's graduate program.