CU Boulder offers two PhD research settings that may be of interest, JILA, which is a joint venture between NIST fellows and CU physics and chemistry professors: https://jila.colorado.edu/
JILA gets NSF funding, and works on Bose Einstein condensates and many other areas of physics including quantum devices and optical devices. Dr. Eric Cornell is a NIST Fellow at JILA who accepts PHD and post docs and won the Nobel prize for Bose Einstein Condensate work.
There are many other good PhD mentors at JILA, the CU Physics Department and CU Department of Applied Mathematics to choose from. NIST Fellows work exclusively on the CU Boulder campus at JILA, mentor PhD students but do not have to teach, so they focus exclusively on their PhD and post docs.
About a mile from the CU campus, the National Institute of Standards and Technology has a laboratory on Broadway and Baseline Road in Boulder.
NIST is part of the US Department of Commerce and trains some theoretical and experimental PhD students at CU, in areas like superconductivity, laser trapping of ions and atoms. You do not need to be a US citizen to work on a PhD at NIST Boulder. While some NIST physicists are jointly appointed to CU Boulder Department of Physics, most work exclusively on their research work. There is theoretical and experimental work on quantum bits and circuits, magnetic devices, superconducting devices, single photon counters, optical devices and superconducting sensors for cosmology research on South pole and other telescopes. (See Dr. Gene Hilton). There is a state of the art clean room, and lots of low temperature physics equipment such as dilution refrigerators, to do experiments at a few degrees Kelvin. The atomic clock resides at NIST and time and frequency research is conducted there as well. Dr. David Wineland, a physicist at NIST in Boulder recently won a Nobel Prize for his work on laser cooling trapped ions, a quantum phenomena. Dr. Wineland is known as an amazing PhD advisor:http://www.colorado.edu/today/2012/10/0 ... e-students
CU Boulder is located in a city of 100,000, which is about 30 miles north of Denver, and the international airport.