Precision Measurements with Laser-cooled Cadmium: Optical-Lattice Clock and Cold Collision Experiments

The project will develop experimental techniques for optical-frequency atomic clocks based on cadmium, an attractive candidate for the next generation of atomic clocks and an anticipated redefinition of international atomic time. Atomic clocks are the most accurate quantum sensors and use long coherence times important for many quantum sensors and quantum information science. The small tick-rate differences and the short time intervals that atomic clock routinely measure have wide-ranging applications, including the Global Positioning System (GPS), secure financial transactions, and official U.S. and international time. Scientific applications of atomic clocks include tests of general relativity and fundamental physics, geodesy, long baseline interferometry, and metrology. Atomic clocks may probe Dark Matter and address questions such as whether fundamental constants, for example the ratio of the mass of an electron and the mass of a proton, change in time. Just after the big bang, were fundamental constants different than they are now? The attractiveness of cadmium atoms for highly accurate clocks and other precision measurements stems from an insensitivity of a suitable excitation of the atoms to thermal radiation from room-temperature surroundings, a limitation for many atomic clocks. Additionally, a practical aspect is that the lasers needed to make a cadmium clock are expected to be more reliable than for other clock species with small thermal sensitivities. Cadmium also has a long series of eight isotopes that can be used to search for physics with new fundamental forces. The isotopes have significantly different atom-atom collisions at the low temperatures used in clocks, within a millionth of a degree of absolute zero. The cadmium isotopes include multiple bosons and fermions, which have different behaviors at ultra-cold temperatures. At such temperatures, the quantum-mechanical nature of atomic gases becomes evident and the basic-science of these gases is of broad interest in modern physics research. The project will provide training of graduate students in many areas of modern technology, including lasers, non-linear optics, the generation of coherent ultraviolet light, radio-frequency and microwave techniques, ultra-high vacuum, and atomic clocks and frequency control. Specific goals for this research program include investigating higher order frequency shifts due to the optical lattice light in different lattice configurations and studying the ultracold scattering of the cadmium isotopes. The lattice light frequency shifts depend non-linearly on the intensity due to magnetic dipole and electric quadrupole transitions, and the small hyperpolarizability of cadmium from two-photon transitions. Different lattice configurations can reduce tunneling between lattice sites at low lattice intensities, leading to smaller Doppler and lattice light shifts. The different configurations allow the light shifts to be studied and higher clock accuracy. Another important component of the project is collaborations with atomic clock groups around the world, for example, to evaluate the accuracies of primary atomic clocks that contribute to International Atomic Time (TAI). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2607988 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Kurt Gibble | Institution: Pennsylvania State Univ University Park, UNIVERSITY PARK, PA | Award Amount: $743,777 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2607988 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2607988.html