Synthesis of supramolecular host architectures for rare-earth guests: New platforms for quantum technology

Abstract

An unmet need in quantum technology is the development of a single-photon source with low loss and long coherence lifetime. The ability of a device to efficiently store and retrieve single photons is currently the limiting factor in quantum information processing. A novel solution to this problem is the use of a lanthanide ion isolated as a host-guest complex that provides a defined environment, reducing the problem of quantum decoherence. Due to their unique electronic properties, lanthanide ions have previously been investigated for use in quantum technology.a, b However, the use of a lanthanide complex as a source of single photons has yet to be demonstrated. To create a low-loss system the rare-earth complex would need to be incorporated into an optical cavity. Two different approaches were followed, initially the photophysics experiments were developed around simple tetrakis lanthanide complexes (Chapter 2). These complexes were investigated by spectroscopic characterisation and Judd-Ofelt (J-O) analysis. This analysis can in future be applied to more complicated structures and architectures. These complexes were then successfully integrated into an optical fibre-coupled setup which is promising for the design and fabrication of an optical-fibre coupled device for single-photon production. Figure i: Tetrakis lanthanide DBM complexes were synthesised and used for optics experiments. However, the ultimate goal is to produce a cage that fully encapsulates the lanthanide ion, and to achieve this, a series of fluorinated cage structures have been proposed, such as the example in Figure ii. The triazolo cages are hypothesised to have the required optical properties in addition to binding strongly to lanthanide ions. The target compounds feature six fluorotriazole motifs with the fluorine lone pair binding to the central rare-earth in addition to either three phenol or three pyridine donors. These structures were simulated using density functional theory (DFT) computational modelling and progress has been made in the multi-step synthesis of ligands and architectures based on these designs. Figure ii: DFT simulation of target triazolo cage binding to a europium ion with both fluorine and nitrogen donor atoms.

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Identifiers

ORCID for Sam Thompson: orcid.org/0000-0001-6267-5693

ORCID for James Gates: orcid.org/0000-0001-8671-5987

ORCID for Bill Brocklesby: orcid.org/0000-0002-2123-6712

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