Implementation of the Quantum Fourier Transform on a molecular qudit with full refocusing and state tomography

TL;DR

This paper demonstrates implementing the Quantum Fourier Transform on a molecular spin qudit, showcasing high-fidelity control and state tomography, thus proving the feasibility of quantum logic in molecular spin systems.

Contribution

It introduces a full-refocusing protocol for molecular spin qudits and experimentally implements QFT, advancing quantum control in chemically tunable multi-level systems.

Findings

Successful implementation of QFT on a molecular qudit

High-fidelity state recovery using full-refocusing protocol

Insights into inhomogeneous broadening mechanisms

Abstract

Molecular spin qudits based on lanthanide complexes offer a promising platform for quantum technologies, combining chemical tunability with multi-level encoding. However, experimental demonstrations of their envisaged capabilities remain scarce, posing the difficulty of achieving precise control over coherences between qudit states in long pulse sequences. Here, we implement in 173Yb(trensal) qudit the Quantum Fourier Transform (QFT), a core component of numerous quantum algorithms, storing quantum information in the phases of coherences. QFT provides an ideal benchmark for coherence manipulation and an unprecedented challenge for molecular spin qudits. We address this challenge by embedding a full-refocusing protocol for spin qudits in our algorithm, mitigating inhomogeneous broadening and enabling a high-fidelity recovery of the state. Complete state tomography demostrates the performance of the algorithm, while simulations provide insight into the physical mechanisms behind inhomogeneous broadening. This work shows the feasibility of quantum logic on molecular spin qudits and highlights their potential.