Telecom-Band Rotational Cooling of a Heavy Molecular Ion

Northwestern University, Evanston IL

Investigators

Abstract

This project is for developing a simple and inexpensive technique to use lasers to control the quantum state of molecular ions held in radiofrequency traps. One thrust of modern physics research is to gain full quantum control over increasingly complex objects. Applications of such control include quantum information processing, quantum-controlled chemistry studies, and improved searches for dark matter and other physics beyond the Standard Model of elementary particles and fields. Great success has been achieved in using lasers to control quantum states of trapped atoms, but it is only recently that laser techniques to control trapped molecules have become available. In this project researchers will develop the first use of inexpensive telecom-band lasers to optically control the quantum states of a new species of molecular ion, singly-ionized Tellurium Hydride (TeH+). This will develop new technology needed for fundamental physics studies, and it will train graduate students in atomic, molecular and optical physics research methods. Besides having the right structure to allow telecom-band optical control, TeH+ is of astrophysical interest because Tellurium (Te) serves as a probe for testing models of heavy element formation in stars and was in fact observed in spectra from the recent kilonova event jointly detected by LIGO. TeH+ should be one of the most abundant Te-containing species in space, but its use as a marker first requires the observation of its spectrum in a laboratory. TeH+ is also an attractive species for ion trap applications, not only because of the potential for inexpensive state control, but also because of its intrinsic properties. Being significantly heavier than most other molecular ions previously investigated for state control, it would have lower motional heating rates in quantum information processing applications and smaller second-order Doppler shifts in precision measurements. Furthermore, TeH+ also has long-lived vibrational states and a deep vibrational well, making its high vibrational overtone transitions attractive candidates for optical-frequency probes of time-variation of the proton-electron mass ratio. In this work, the researchers will produce TeH+ in a molecular beam and will perform the first experimental measurements of its spectroscopic properties. They will then demonstrate rotational optical pumping in various schemes designed to optimize either simplicity and cost or state preparation efficiency or speed. 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.