Quantum entanglement between an atom and a molecule

TL;DR

This paper demonstrates entanglement between a molecule and an atom, showing molecules' potential to transduce quantum information across diverse frequencies for advanced quantum applications.

Contribution

First experimental demonstration of entanglement between a molecular ion's rotational states and an atomic ion's internal states, showcasing molecular qubits' versatility.

Findings

Successfully entangled molecular and atomic ion states

Molecular qubits operated at 13.4 kHz and 855 GHz frequencies

Highlights molecules' role in hybrid quantum systems

Abstract

Conventional information processors freely convert information between different physical carriers to process, store, or transmit information. It seems plausible that quantum information will also be held by different physical carriers in applications such as tests of fundamental physics, quantum-enhanced sensors, and quantum information processing. Quantum-controlled molecules in particular could transduce quantum information across a wide range of quantum-bit (qubit) frequencies, from a few kHz for transitions within the same rotational manifold, a few GHz for hyperfine transitions, up to a few THz for rotational transitions, to hundreds of THz for fundamental and overtone vibrational and electronic transitions, possibly all within the same molecule. Here, we report the first demonstration of entanglement between states of the rotation of a $\rm^{40}CaH^+$ molecular ion and internal states of a $\rm^{40}Ca^+$ atomic ion. The qubit addressed in the molecule has a frequency of either 13.4 kHz or 855 GHz, highlighting the versatility of molecular qubits. This work demonstrates how molecules can transduce quantum information between qubits with different frequencies to enable hybrid quantum systems. We anticipate that quantum control and measurement of molecules as demonstrated here will create opportunities for quantum information science, quantum sensors, fundamental and applied physics, and controlled quantum chemistry.