Synthetic Hilbert Space Engineering of Molecular Qudits: Isotopologue Chemistry

Abstract

One of the most ambitious technological goals is the development of devices working under the laws of quantum mechanics. Among others, an important challenge to be resolved on the way to such breakthrough technology concerns the scalability of the available Hilbert space. Recently, proof‐of‐principle experiments were reported, in which the implementation of quantum algorithms (the Grover's search algorithm, iSWAP‐gate, etc.) in a single‐molecule nuclear spin qudit (with d = 4) known as 159TbPc2 was described, where the nuclear spins of lanthanides are used as a quantum register to execute simple quantum algorithms. In this progress report, the goal of linear and exponential up‐scalability of the available Hilbert space expressed by the qudit‐dimension “d” is addressed by synthesizing lanthanide metal complexes as quantum computing hardware. The synthesis of multinuclear large‐Hilbert‐space complexes has to be carried out under strict control of the nuclear spin degree of freedom leading to isotopologues, whereby electronic coupling between several nuclear spin units will exponentially extend the Hilbert space available for quantum information processing. Thus, improved multilevel spin qudits can be achieved that exhibit an exponentially scalable Hilbert space to enable high‐performance quantum computing and information storage.

Quantum tunnelling of the magnetisation in single-molecule magnet isotopologue dimers

“…These finding must be contemplated for Ln-SMMs proposed for very low temperature applications, such as quantum bits, where the utilisation of the nuclear states embedded in the lanthanide ions can be used as quantum bits. For example, the indirect coupling of the nuclear states, via the electronic states, would increase the number of nuclear states available for the realisation of complex quantum algorithms 24…”

Quantum state manipulation of single atom magnets using the hyperfine interaction

“…As classical magnetic bits, SAMs and SMMs have demonstrated magnetic bistability [1,3,4,8], even above liquid nitrogen temperatures [5], readability and writability [1,[9][10][11][12], and self-assembly into periodic arrays [4,8]. For quantum information processing, the precise control over their local environment, intrinsic isolation, and relative ease of on-surface deposition render SAMs and SMMs attractive qubit candidates [13][14][15][16][17][18][19][20]. Early experiments have shown promise, so far culminating with an experimental realization of Grover's search algorithm on a single molecule [7].…”

Strangely attractive: Collaboration and feedback in the field of molecular magnetism

“…[ 1 ] Because of these remarkable properties, which are controllable at the molecular scale, SMMs have been proposed as potential candidates for high‐density magnetic storage, as well as qubits for the practical implementation of quantum computing. [ 2 ] One figure of merit for SMMs is the “blocking temperature” ( T B ), often defined as the temperature at which the characteristic magnetic relaxation time ( τ ) is 100 seconds ( τ = 100 s). We choose this parameter here as it is widely used in the literature, although there are other metrics with which to compare the performance of these materials.…”