Searcharxiv⌕ Search

arXiv subjects

Andrew J. Baldwin

Publications and source records attributed to Andrew J. Baldwin.

4 recordsLinked to original sources

Phase-only control of GRAPE shaped pulses

We compare phase-only control with phase-and-amplitude control when designing shaped pulses using the GRAPE algorithm, and explain why phase-only control has significant advantages. Trotterisation can be used to simulate amplitude modulation with phase modulation, indicating that the two approaches are fundamentally equivalent. Pulses designed by either method can be interconverted, but phase-only optimization is faster and simpler. The resulting pulses can then be converted into phase-and-amplitude form for more robust implementation if desired.

quant-ph↗

Temporal Entanglement and Witnesses of Non-Classicality

The universality of quantum theory has been questioned ever since it was proposed. Key to this long-unsolved question is to test whether a given physical system has non-classical features. Here we connect recently proposed witnesses of non-classicality, based on information-theoretic ideas, with the theory of temporal entanglement. We provide a protocol to witness the non-classicality of a system by probing it with a qubit: we show that, assuming a general conservation law, violating temporal Bell inequalities on the qubit probe implies the non-classicality of the system under investigation. We also perform proof-of-principle experimental emulations of the proposed witness of non-classicality, using a three qubit Nuclear Magnetic Resonance quantum computer. Our result is robust, as it relies on minimal assumptions, and remarkably it can be applied in a broad range of contexts, from quantum biology to quantum gravity.

quant-ph↗

Mesoscopic heterogeneity in biomolecular condensates from sequence patterning

Biomolecular condensates composed of intrinsically disordered proteins (IDPs) are vital for proper cellular function, and their dysfunction is associated with diseases including neurodegeneration and cancer. Despite their biological importance, the precise physical mechanisms underlying condensate (dys)function are unclear, in part owing to the difficulties in understanding how biomolecular sequence patterns influence emergent condensate behaviours across relevant length and timescales. Here, through minimal physical modelling, we explain how IDP sequence patterning gives rise to nano-scale organisational heterogeneities in condensates. By applying our coarse-grained molecular-dynamics polymer model, which accounts for steric, attractive, and electrostatic interactions, we systematically quantify and map out the emergent morphological phases resulting from a wide range of sequence patterns. We demonstrate how sequences that enable local coil-to-globule transitions within regions of single polymers - driven by a competition between the preferred crowding densities of different regions in the sequence - also exhibit cluster formation in condensates. Overall, our work provides a conceptual framework to understand how sequence properties determine mesoscopic organisation within biomolecular condensates.

cond-mat.soft↗

Efficiently computing the Uhlmann fidelity for density matrices

We consider the problem of efficiently computing the Uhlmann fidelity in the case when explicit density matrix descriptions are available. We derive an alternative formula which is simpler to evaluate numerically, saving a factor of 10 in time for large matrices.

quant-ph↗