Coherent coupling and non-destructive measurement of trapped-ion mechanical oscillators

TL;DR

This paper demonstrates coherent, high-fidelity quantum control and non-destructive measurement of trapped-ion motional modes, enabling advanced quantum operations and improving their potential for quantum computing applications.

Contribution

It introduces a method for coherent exchange of motional quanta between separated modes and achieves non-destructive measurements, advancing trapped-ion quantum technology.

Findings

High-fidelity quantum state transfer achieved

Demonstration of motional entanglement and interference

Repeated non-destructive measurement of motional states

Abstract

Precise quantum control and measurement of several harmonic oscillators, such as the modes of the electromagnetic field in a cavity or of mechanical motion, are key for their use as quantum platforms. The motional modes of trapped ions can be individually controlled and have good coherence properties. However, achieving high-fidelity two-mode operations and nondestructive measurements of the motional state has been challenging. Here we demonstrate the coherent exchange of single motional quanta between spectrally separated harmonic motional modes of a trapped-ion crystal. The timing, strength, and phase of the coupling are controlled through an oscillating electric potential with suitable spatial variation. Coupling rates that are much larger than decoherence rates enable demonstrations of high fidelity quantum state transfer and beamsplitter operations, entanglement of motional modes, and Hong-Ou-Mandel-type interference. Additionally, we use the motional coupling to enable repeated non-destructive projective measurement of a trapped-ion motional state. Our work enhances the suitability of trapped-ion motion for continuous-variable quantum computing and error correction and may provide opportunities to improve the performance of motional cooling and motion-mediated entangling interactions.