OAR@UM Collection:

Deterministic quantum computation with one-clean-qubit model as an open quantum system

Sun, 01 Jan 2023 00:00:00 GMT

Title: Deterministic quantum computation with one-clean-qubit model as an open quantum system Authors: Xuereb, Jake; Campbell, Steve; Goold, John; Xuereb, Andre Abstract: The deterministic quantum computation with one-clean-qubit model (DQC1) complexity class, or power-ofone qubit model, is examined as an open quantum system.We study the dynamics of a register of qubits carrying out a DQC1 algorithm and show that, for any algorithm in the complexity class, the evolution of the logical qubit can be described as an open quantum system undergoing a dynamics which is unital. Unital quantum channels respect the Tasaki-Crooks fluctuation theorem, and we demonstrate how this is captured by the thermodynamics of the logical qubit. As an application, we investigate the equilibrium and nonequilibrium thermodynamics of the DQC1 trace estimation algorithm. We show that different computational inputs, i.e., different traces being estimated, lead to different energetic exchanges across the register of qubits and that the temperature of the logical qubit impacts the magnitude of fluctuations experienced and quality of the algorithm.

The JWST hubble sequence : the rest-frame optical evolution of galaxy structure at 1.5
Sun, 01 Jan 2023 00:00:00 GMT
Title: The JWST hubble sequence : the rest-frame optical evolution of galaxy structure at 1.5 109 M⊙ at z > 3 are not dominated by irregular and peculiar structures, either visually or quantitatively, as previously thought. We find a strong dominance of morphologically selected disk galaxies up to z = 6 in this mass range. We also find that the stellar mass and star formation rate densities are dominated by disk galaxies up to z ∼ 6, demonstrating that most stars in the Universe were likely formed in a disk galaxy. We compare our results to theory to show that the fraction of types we find is predicted by cosmological simulations, and that the Hubble Sequence was already in place as early as one billion years after the Big Bang. Additionally, we make our visual classifications public for the community.

Variational Gibbs state preparation on NISQ devices

Sun, 01 Jan 2023 00:00:00 GMT

Title: Variational Gibbs state preparation on NISQ devices Abstract: The preparation of an equilibrium thermal state of a quantum many-body system on noisy intermediate-scale quantum (NISQ) devices is an important task in order to extend the range of applications of quantum computation. Faithful Gibbs state preparation would pave the way to investigate protocols such as thermalization and out-of-equilibrium thermodynamics, as well as providing useful resources for quantum algorithms, where sampling from Gibbs states constitutes a key subroutine. We propose a variational quantum algorithm (VQA) to prepare Gibbs states of a quantum many-body system. The novelty of our VQA consists in implementing a parameterized quantum circuit acting on two distinct, yet connected (via CNOT gates), quantum registers. The VQA evaluates the Helmholtz free energy, where the von Neumann entropy is obtained via post-processing of computational basis measurements on one register, while the Gibbs state is prepared on the other register, via a unitary rotation in the energy basis. Finally, we benchmark our VQA by preparing Gibbs states of the transverse field Ising and Heisenberg XXZ models and achieve remarkably high fidelities across a broad range of temperatures in statevector simulations. We also assess the performance of the VQA on IBM quantum computers, showcasing its feasibility on current NISQ devices.

EPOCHS VI : the size and shape evolution of galaxies since z ∼8 with JWST observations

Mon, 01 Jan 2024 00:00:00 GMT

Title: EPOCHS VI : the size and shape evolution of galaxies since z ∼8 with JWST observations Authors: Ormerod, Katherine; Conselice, Christopher J.; Adams, Nathan J.; Harvey, Thomas A.; Austin, Duncan; Trussler, James A.A.; Ferreira, Leonardo De Albernaz; Caruana, Joseph; Lucatelli, Geferson; Li, Qiong; Roper, William J. Abstract: We present the results of a size and structural analysis of 1395 galaxies at 0.5 ≤ z ≲ 8 with stellar masses log (M*/M⊙)> 9.5 within the James Webb Space Telescope Public CEERS field that overlaps with the Hubble Space Telescope Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey EGS observations. We use GALFIT to fit single Sérsic models to the rest-frame optical profile of our galaxies, which is a mass-selected sample complete to our redshift and mass limit. Our primary result is that at fixed rest-frame wavelength and stellar mass, galaxies get progressively smaller, evolving as ∼(1 + z)−0.71 ± 0.19 up to z ∼ 8. We discover that the vast majority of massive galaxies at high redshifts have low Sérsic indices, thus do not contain steep, concentrated light profiles. Additionally, we explore the evolution of the size–stellar mass relationship, finding a correlation such that more massive systems are larger up to z ∼ 3. This relationship breaks down at z > 3, where we find that galaxies are of similar sizes, regardless of their star formation rates and Sérsic index, varying little with mass. We show that galaxies are more compact at redder wavelengths, independent of sSFR or stellar mass up to z ∼ 3. We demonstrate the size evolution of galaxies continues up to z ∼ 8, showing that the process or causes for this evolution is active at early times. We discuss these results in terms of ideas behind galaxy formation and evolution at early epochs, such as their importance in tracing processes driving size evolution, including minor mergers and active galactic nuclei activity.