Quantum non-demolition state detection and spectroscopy of single trapped molecules

TL;DR

This paper demonstrates a quantum-non-demolition protocol for detecting and spectroscopically analyzing single trapped N$_2^+$ molecules with high fidelity, enabling advanced control and measurement of molecular quantum states.

Contribution

It introduces a novel quantum-non-demolition method for single-molecule detection and spectroscopy, advancing control over molecular quantum states.

Findings

Spin-rovibronic state detected with >99% fidelity

Spectroscopic transition position and strength determined non-destructively

Method enables new molecular quantum control and spectroscopy approaches

Abstract

Trapped atoms and ions are among the best controlled quantum systems which find widespread applications in quantum information, sensing and metrology. For molecules, however, a similar degree of control is currently lacking owing to their complex energy-level structure. Quantum-logic protocols in which atomic ions serve as probes for molecular ions are a promising route for achieving this level of control, especially with homonuclear molecules that decouple from black-body radiation. Here, a quantum-non-demolition protocol on single trapped N$_2^+$ molecules is demonstrated. The spin-rovibronic state of the molecule is detected with more than 99% fidelity and the position and strength of a spectroscopic transition in the molecule are determined, both without destroying the molecular quantum state. The present method lays the foundations for new approaches to molecular precision spectroscopy, for state-to-state chemistry on the single-molecule level and for the implementation of molecular qubits.