Quantum Control of Single Polyatomic Molecules

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

The molecules which surround us typically occupy millions of distinct quantum states - for example, individual molecules in the air are moving and spinning in many different directions. In order to take advantage of the quantum properties of these molecules, one needs to learn how to prepare individual molecules in a single quantum state, and to measure which state they are in. This will require absolute control over the movement and rotation of the molecule. Today, physicists can prepare atoms in single quantum states, and measure which state they are in with high fidelity. This ability underpins many of the recent advances in atomic physics. The ability to prepare and measure the state of molecules lags far behind, and no molecule containing more than two atoms has ever been prepared in a single quantum state. This project, funded by the Atomic, Molecular and Optical Physics Program of the Division of Physics, and the Chemical Structure, Dynamics and Mechanisms-A Program of the Division of Chemistry, develops the tools for this goal. An important application of this work is that it will enable the identification of individual molecules without destroying them, including identifying the chirality of these molecules. Chirality is the subtle difference between left-handed or right-handed molecules that can play a big role in how the molecule functions, for example in pharmaceuticals. This work will be done by graduate and undergraduate students at the University of California Santa Barbara (UCSB), including financially disadvantaged students enrolled in UCSB's EUREKA program. The program will allow these students to gain valuable, hands-on scientific skills while earning stipends that allow them to stay in school. The scientists leading this research have proposed a set of methods that will allow them to control a broad range of molecular ions at the single quantum state level. The centerpiece of this proposal is a new state readout method, quantum bolometry, which leverages the rich internal level structure of these molecules to provide high-fidelity quantum state readout of individual molecules. A single molecular ion will be trapped in a hybrid Paul trap/optical lattice, along with a single laser-cooled strontium ion. The molecular ion's motion will be driven via a combination of a state-dependent optical lattice and rotational transitions within the molecule which are driven directly via microwave-frequency electric fields. The method does not require sideband resolution or ground state cooling, in contrast to related quantum logic spectroscopy methods. Quantum bolometry can be applied to most reasonably small (4 - 15 atoms), nonspherical polyatomic ions. These methods will allow for non-destructive measurement of the isomer and enantiomer of individual molecules for the first time, and allow for spectroscopy with a resolution significantly greater than existing ensemble molecular spectroscopy techniques. Spectroscopy at this level would represent our most accurate determination of molecular structure. 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.