Method for preparation and readout of polyatomic molecules in single quantum states

摘要

Polyatomic molecular ions containmany desirable attributes of a useful quantum system, including rich internal degrees of freedom and highly controllable coupling to the environment. To date, the vastmajority of state-specific experimental work on molecular ions has concentrated on diatomic species. The ability to prepare and read out polyatomic molecules in single quantum states would enable diverse experimental avenues not available with diatomics, including new applications in precision measurement, sensitive chemical and chiral analysis at the single-molecule level, and precise studies of Hz-level molecular tunneling dynamics.While cooling the motional state of a polyatomic ion via sympathetic cooling with a laser-cooled atomic ion is straightforward, coupling this motional state to the internal state of the molecule has proven challenging. Here we propose a method for readout and projectivemeasurement of the internal state of a trapped polyatomic ion. Themethod exploits the rich manifold of technically accessible rotational states in the molecule to realize robust state preparation and readout with far less stringent engineering than quantum logicmethods recently demonstrated on diatomic molecules. The method can be applied to any reasonably small (?10 atoms) polyatomic ion with an anisotropic polarizability.