Modelling Conformational Flexibility in a Spectrally Addressable Molecular Multi‐Qubit Model System

Abstract

Dipolar coupled multi‐spin systems have the potential to be used as molecular qubits. Herein we report the synthesis of a molecular multi‐qubit model system with three individually addressable, weakly interacting, spin 1/2 ${{ 1/2 }}$ centres of differing g‐values. We use pulsed Electron Paramagnetic Resonance (EPR) techniques to characterise and separately address the individual electron spin qubits; CuII, Cr7Ni ring and a nitroxide, to determine the strength of the inter‐qubit dipolar interaction. Orientation selective Relaxation‐Induced Dipolar Modulation Enhancement (os‐RIDME) detecting across the CuII spectrum revealed a strongly correlated CuII‐Cr7Ni ring relationship; detecting on the nitroxide resonance measured both the nitroxide and CuII or nitroxide and Cr7Ni ring correlations, with switchability of the interaction based on differing relaxation dynamics, indicating a handle for implementing EPR‐based quantum information processing (QIP) algorithms.

Weak Exchange Interactions in Multispin Systems: EPR Studies of Metalloporphyrins Decorated with {Cr7Ni} Rings

“…Qubits are the fundamental building blocks for any future quantum information processing (QIP) . Much progress has been made in improving the performance of qubits based on electron spins in molecules, , with coherence times reaching many microseconds, even at room temperature. − For such qubits to be used to implement more complex logical operations than can be achieved with single-qubits, they need to be brought together into multiqubit architectures. , Some work in this direction has been published, but much remains to be done, particularly in bringing together different qubits that could offer greater functionality than using the same qubit repeatedly. ,,,− For example, qubits with different g -values could be addressed or measured separately. ,,, …”

“…The {Cr 7 Ni} rings have long been studied as qubits and as components of multiqubit molecules. ,,,,− Here we have studied the chiral [Cr 7 NiF 3 ( N -Etglu)(O 2 C t Bu) 15 L] rings ( N -EtgluH 5 = N -ethyl- d - glucamine; L = a monodentate ligand), which are purple in color . The monodentate ligand, L, is attached to the divalent Ni 2+ center and can be displaced to link the purple rings.…”

Direct Comparison between Förster Resonance Energy Transfer and Light-Induced Triplet–Triplet Electron Resonance Spectroscopy

“…The choice of orthogonal chromophores provides a significant improvement in data quality compared to the initial homo-LITTER experiments. Furthermore, the selective optical addressability of each chromophore has the potential to enable unambiguous determination of the PDS distance in systems with more than two labels, without the interference of multispin effects. , Optical orthogonality is easier to achieve and allows a wider choice of labels than spin-label orthogonality. − Therefore, 2-color LITTER offers a promising route to controlling complexity in PDS of multispin systems. There is also the potential for increasing the modulation depth by further reducing the spectral overlap and unwanted excitations by choosing different chromophore pairs and excitation wavelengths.…”