ORCID Profile
0000-0002-2923-1596
Current Organisation
The University of Auckland
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Publisher: IOP Publishing
Date: 26-05-2022
Abstract: In this work, we investigate the parameters governing the rate at which a quantum channel arises at the onset of an interaction between two systems, A and B . In particular, when system A is pre-entangled with an ancilla, A ~ , we quantify the early-time transmission of pre-existing entanglement by calculating the leading order change in coherent information of the complementary channel ( A → B ′). We show that, when A and B are initially unentangled and B is pure, there is no change in coherent information to first order, while the leading (second) order change is ergent. However, this ergence may be regulated by embedding the conventional notion of coherent information into what we call the family of n -coherent informations, defined using n -Rényi entropies. We find that the rate of change of the n -coherent information at the onset of the interaction is governed by a quantity, which we call the n -exposure, which captures the extent to which the initial coherent information of A with A ~ is exposed to or ‘seen by’ the interaction Hamiltonian between A and B . We give ex les in qubit systems and in the light–matter interaction.
Publisher: American Physical Society (APS)
Date: 17-04-2023
Publisher: Oxford University Press (OUP)
Date: 12-09-2023
Publisher: IOP Publishing
Date: 10-2020
Abstract: At the onset of an interaction between two initially independent systems, each system tends to experience an increase in its n -Rényi entropies, such as its von Neumann entropy ( n = 1) and its mixedness ( n = 2). We here ask which properties of a system determine how quickly its Rényi entropies increase and, therefore, how sensitive the system is to becoming entangled. We find that the rate at which the n -Rényi entropy increases in an interaction is determined by a quantity which we term the n -fragility of the system. The 2-fragility is closely related to the notion of 2-norm coherence, in that it too quantifies the extent to which a density matrix is ‘off-diagonal’ with respect to the eigenbasis of a reference operator. Nevertheless, the 2-fragility is not a coherence monotone in the resource theoretic sense since it depends also on the eigenvalues of the reference operator. It is this additional sensitivity to the eigenvalues of the reference operator, here the interaction Hamiltonian, which enables the 2-fragility to quantify the rate of entropy production in interactions. We give an ex le using the light–matter interaction and we anticipate applications to the study of the rates at which two systems exchange classical and quantum information when starting to interact.
Publisher: IOP Publishing
Date: 16-10-2018
Publisher: American Physical Society (APS)
Date: 07-04-2023
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.3
Abstract: The core-cusp problem is a widely cited motivation for the exploration of dark matter models beyond standard cold dark matter. One such alternative is ultralight dark matter (ULDM), extremely light scalar particles exhibiting wavelike properties on kiloparsec scales. Astrophysically realistic ULDM halos are expected to consist of inner solitonic cores embedded in NFW-like outer halos. The presence of the solitonic core suggests that ULDM may resolve the core-cusp discrepancy associated with pure NFW halos without recourse to baryonic physics. However, it has been demonstrated that the density of ULDM halos can exceed those of comparable NFW configurations at some radii and halo masses, apparently exacerbating the problem rather than solving it. This situation arises because, although solitonic cores are flat at their centres, they obey an inverse mass–radius scaling relationship. Meanwhile, the mass of the inner soliton increases with the total halo mass, and therefore the inner core becomes more peaked at large halo masses. We describe a parameterisation of the radial density profiles of ULDM halos that allows for environmental variability of the core–halo mass relation in order to investigate this issue in more detail. For halos up to $10^{12} {\\rm M}_\\odot$ , we find feasible ULDM profiles for which the central density is lower than their NFW counterparts at astrophysically accessible radii. However, comparisons to observed profiles do not strongly favour either option both give reasonable fits to subsets of the data for some parameter choices. Consequently, we find that robust tests of the core-cusp problem in ULDM will require more comprehensive observational data and simulations that include baryonic feedback.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Emily Kendall.