A dissymmetric [Gd$_{2}$] coordination molecular dimer hosting six addressable spin qubits

TL;DR

This paper reports the design and characterization of a dissymmetric Gd(III) molecular dimer that hosts six addressable spin qubits, advancing molecular quantum computing by increasing the computational space and demonstrating coherent control.

Contribution

It introduces a novel dissymmetric Gd(III) dimer capable of acting as a 64-dimensional spin qudit with fully controllable quantum states, expanding the potential of molecular spin qubits.

Findings

Realization of a 64-dimensional spin qudit from a Gd(III) dimer.

Coherent control of spin states demonstrated with microsecond coherence times.

Distinct zero-field splittings achieved through local coordination symmetry.

Abstract

Artificial magnetic molecules are suitable hosts to one or several spin qubits, which could then implement small-scale algorithms. In order to become of practical use, such molecular spin processors need to increase the dimension $d$ of the available computational space and fulfill the highly demanding conditions that warrant universal operations. Here, we design, synthesize and fully characterize dissymetric molecular dimers hosting either one or two Gd(III) ions. The strong sensitivity of Gd(III) magnetic anisotropy to the symmetry of its local coordination gives rise to different zero-field splittings at each coordination site. As a result, the [LaGd] and [GdLu] complexes provide realizations of distinct $d = 8$ spin qudits, whereas the [Gd$_{2}$] dimer meets all requirements, including a complete set of operations, to act as a $d = 64$ all-electron spin qudit (or, equivalenty, as six addressable qubits). Electron paramagnetic resonance experiments show that the relevant resonant transitions between different spin states can be coherently controlled, with coherence times T$_{M}$ of the order of $1$ $\mu$s limited by intramolecular hyperfine interactions. Coordination complexes with embedded quantum functionalities are promising building blocks for quantum computation and simulation hybrid platforms.