arXiv subjects

Alistair J. Fielding

Publications and source records attributed to Alistair J. Fielding.

4 recordsLinked to original sources

arXiv2019

Realization of Universal Quantum Gates with Spin-Qudits in Colloidal Quantum Dots

We exploit hyperfine interactions in a single Mn-ion confined in a quantum dot (QD) to create a qudit, i.e. a multi-level quantum-bit system, with well defined, addressable and robust set of spin states for the realization of universal quantum gates. We generate and probe an arbitrary superposition of states between selected hyperfine energy level pairs by using electron double resonance detected nuclear magnetic resonance (EDNMR). This enables the observation of Rabi oscillations and the experimental realization of NOT and SWAP universal quantum gates that are robust against decoherence. Our protocol for cyclical preparation, manipulation and read-out of logic gates offers opportunities for integration of qudits in scalable quantum circuit architectures beyond solid state electron spin qubits.

cond-mat.mes-hall↗

arXiv2016

MD and EPR studies of the structure and dynamics of the MTSL spin-labelled activation loop of the Aurora-A kinase

The understanding of kinase structure is mostly based on protein crystallography, which is limited by the requirement to trap molecules within a crystal lattice. Therefore, characterisations of the conformational dynamics of the activation loop in solution are important to enhance the understanding of molecular processes related to diseases and to support the discovery of small molecule kinase inhibitors. In this work, we demonstrated that long molecular dynamics simulations exhaustively sampled all the conformational space of the activation loop of the Aurora-A kinase and of the methane-thiosulfonate spin label, introduced into the activation loop for the electron paramagnetic measurements. MD was used to determine structural fluctuations, order parameters and rotational correlation times of the motion of the activation loop and of the MTSL. Theoretical data obtained were used as input for the calculation of the room temperature 9 GHz continuous wave EPR of the Aurora-A kinase in solution and the comparison between simulated and experimental date revealed that the motion of the protein and spin label occurred on comparable timescales. This work is a starting point for deeper experimental and theoretical studies of the rotational and translational diffusion properties of the Aurora-A kinase protein related to its biological activity.

physics.chem-ph↗

arXiv2016

Density functional theory studies of MTSL nitroxide side chain conformations attached to an activation loop

A quantum-mechanical (QM) method rooted on density functional theory (DFT) has been employed to determine conformations of the methane-thiosulfonate spin label (MTSL) attached to a fragment extracted from the activation loop of Aurora-A kinase. The features of the calculated energy surface revealed low energy barriers between isoenergetic minima and the system could be described in a population of 76 rotamers that can be also considered for other systems since it was found that the X3, X4 and X5 do not depend on the previous two dihedral angles. Conformational states obtained were seen to comparable to those obtained in the α-helix systems studied previously, indicating that the protein backbone does not affect the torsional profiles significantly and suggesting the possibility to use determined conformations for other protein systems for further modelling studies.

physics.chem-ph↗

arXiv2015

Engineering coherent interactions in molecular nanomagnet dimers

Proposals for systems embodying condensed matter spin qubits cover a very wide range of length scales, from atomic defects in semiconductors all the way to micron-sized lithographically-defined structures. Intermediate scale molecular components exhibit advantages of both limits: like atomic defects, large numbers of identical components can be fabricated; as for lithographically defined structures, each component can be tailored to optimize properties such as quantum coherence. Here, we demonstrate what is perhaps the most potent advantage of molecular spin qubits, the scalability of quantum information processing structures using bottom-up chemical self-assembly. Using Cr7Ni spin qubit building blocks, we have constructed several families of two-qubit molecular structures with a range of linking strategies. For each family, long coherence times are preserved, and we demonstrate control over the inter-qubit quantum interactions that can be used to mediate two-qubit quantum gates.

cond-mat.mtrl-sci↗