Nuclear Theory·nucl-th

Wednesday·September 20, 2023

8 papers—4 primary·4 cross-listed

01
Quantum benefit of the quantum equation of motion for the strongly coupled many-body problem
Manqoba Q. Hlatshwayo🇺🇸 · John Novak🇺🇸 · Elena Litvinova🇺🇸
We investigate the quantum equation of motion (qEOM), a hybrid quantum-classical algorithm for computing excitation properties of a fermionic many-body system, with a particular emphasis on the strong-coupling regime. The method is designed as a stepping stone towards building more accurate solutions for strongly coupled fermionic systems, such as medium-heavy nuclei, using quantum algorithms to surpass the current barrier in classical computation. Approximations of increasing accuracy to the exact solution of the Lipkin-Meshkov-Glick Hamiltonian with $N = 8$ particles are studied on digital simulators and IBM quantum devices. Improved accuracy is achieved by applying operators of growing complexity to generate excitations above the correlated ground state, which is determined by the variational quantum eigensolver (VQE). We demonstrate explicitly that the qEOM exhibits a quantum benefit due to the independence of the number of required quantum measurements from the configuration complexity. Post-processing examination shows that quantum device errors are amplified by increasing configuration complexity and coupling strength. A detailed error analysis is presented, and error mitigation based on zero noise extrapolation is implemented.
nucl-thcond-mat.otherquant-phPRC(2024)·14 citations
02
Quark phases in neutron stars consistent with implications of NICER
Y. Yamamoto🇯🇵 · N. Yasutake🇯🇵 · Th.A. Rijken🇯🇵
The analyses for the NICER data imply $R_{2.0 M_{⊙}} = 12.4 1_{- 1.10}^{+ 1.00}$ km and $R_{1.4 M_{⊙}} = 12.5 6_{- 1.07}^{+ 1.00}$ km, indicating the lack of significant variation of the radii from $1.4 M_{⊙}$ to $2.0 M_{⊙}$ . This feature cannot be reproduced by the hadronic matter due to the softening of equation of state (EoS) by hyperon mixing, indicating the possible existence of quark phases in neutron-star interiors. % Two models are used for quark phases: In the quark-hadron transition (QHT) model, quark deconfinement phase transitions from a hadronic-matter EoS are taken into account so as to give reasonable mass-radius ( $M R$ ) curves by adjusting the quark-quark repulsions and the density dependence of effective quark mass. % In the quarkyonic model, the degrees of freedom inside the Fermi sea are treated as quarks and neutrons exist at the surface of the Fermi sea, where $M R$ curves are controlled mainly by the thickness of neutron Fermi layer. % The QHT and quarkyonic EoSs can be adjusted so as to reproduce radii, tidal deformabilities, pressure and central densities inferred from the NICER analysis better than the nucleonic matter EoS, demonstrating the clear impacts of quark phases. Then, the maximum mass for the quakyonic-matter EoS is considerably larger than that for the QHT-matter EoS.
nucl-thastro-ph.HEhep-phPRC(2023)·16 citations
03
Visualizing quantum coherence and decoherence in nuclear reactions
K. Hagino · T. Yoda
Differential cross sections of nuclear reactions often exhibit characteristic oscillations in the angular distribution originated from an interference of two indistinguishable processes. Here we propose a novel method to visualize origins of such oscillations. This is achieved by taking Fourier transform of scattering amplitudes, following the idea in wave optics. We apply this method to elastic scattering of $^{16}$ O+ $^{16}$ O and $^{18}$ O+ $^{18}$ O at energies above the Coulomb barrier. The former system shows strong oscillations in the angular distribution due to the nearside-farside interferences, while the oscillations are largely suppressed in the latter system due to a stronger absorption. We show that the image of the former and the latter systems corresponds to a double-slit and a single-slit problems in quantum mechanics, respectively.
nucl-thhep-phhep-thnucl-exPLB(2024)·5 citations
04
Nuclear descent from the fission barrier in the presence of long--range memory effects
S.V.Radionov
We have investigated the peculiarities of nuclear descent from a parabolic fission barrier within a generalized Langevin equation with power--law $f (t - t^{'}) = (∣ t - t^{'} ∣/ τ)^{- α}$ memory function. We have observed much stronger slowing down of the nuclear descent in the presence of long--range memory effects, caused by the power--law memory function at $0 < α < 1$ , than in the presence of short--range memory effects, generated by exponential $f (t - t^{'}) = exp (- ∣ t - t^{'} ∣/ τ)$ memory function. At a specific value of the exponent $α = 1/2$ of the power--law memory function, it turned out possible to find analytically the trajectory of the descent and demonstrate that the long--range memory effects give rise to complex time oscillations of nuclear shape, becoming more frequent and damped with the correlation time $τ$ . We have found fairly long ( $> 1 0^{- 20} s$ ) times of the descent of $^{236} U$ at the values of the correlation time $τ \sim [1 0^{- 24} \div 1 0^{- 23}] s$ .
nucl-thPRC(2024)·0 citations
05
Nuclear Spectra from Quantum Lanczos Algorithm with Real-Time Evolution and Multiple Reference States
Amanda Bowman🇺🇸
Models of quantum systems scale exponentially with the addition of single-particle states, which can present computationally intractable problems. Alternatively, quantum computers can store a many-body basis of $2^{n}$ dimensions on $n$ qubits. This motivated the quantum eigensolver algorithms developed in recent years, such as the quantum Lanczos algorithm based on the classical, iterative Lanczos algorithm. I performed numerical simulations to find the low-lying eigenstates of $^{20}$ Ne, $^{22}$ Na, and $^{29}$ Na to compare imaginary- and real-time evolution. Though imaginary-time evolution leads to faster convergence, real-time evolution still converges within tens of iterations and satisfies the requirement for unitary operators on quantum computers. Additionally, using multiple reference states leads to faster convergences or higher accuracy for a fixed number of real-time iterations. I performed quantum circuit prototype numerical simulations on a classical computer of the QLanczos algorithm with real-time evolution and multiple reference states to find the low-lying eigenstates of $^{8}$ Be. These simulations were run in both the spherical basis and Hartree-Fock basis, demonstrating that an M-scheme spherical basis leads to lower depth circuits than the Hartree-Fock basis. Finally, I present the quantum circuits for the QLanczos algorithm with real-time evolution and multiple references.
↳ quant-phnucl-th0 citations
06
Status of experimental knowledge on the unbound nucleus $^{13}$ Be
K.L. Jones · J. Kovoor · R. Kanungo
The structure of the unbound nucleus $^{13}$ Be is important to understanding the Borromean, two-neutron halo nucleus $^{14}$ Be. The experimental studies conducted over the last four decades are reviewed in the context of the beryllium chain of isotopes and some significant theoretical studies. One focus of this paper is the comparison of new data from a $^{12}$ Be(d,p) reaction in inverse kinematics, which was analyzed using GEANT4 simulations and a Bayesian fitting procedure, with previous measurements. Two possible scenarios to explain the strength below 1~MeV above the neutron separation energy were proposed in that study: a single $p$ -wave resonance, or a mixture of an $s$ -wave virtual state with a weaker either $p$ -wave or $d$ -wave resonance. Comparisons of recent invariant mass and the (d,p) experiments show good agreement between the transfer measurement and the two most recent high-energy nucleon removal measurements.
↳ nucl-exnucl-thFront.in Phys.(2023)·2 citations
07
Thermodynamics of spin-1/2 fermions on coarse temporal lattices using automated algebra
K. J. Morrell · A. J. Czejdo · N. Carter · J. E. Drut
Recent advances in automated algebra for dilute Fermi gases in the virial expansion, where coarse temporal lattices were found advantageous, motivate the study of more general computational schemes that could be applied to arbitrary densities, beyond the dilute limit where the virial expansion is physically reasonable. We propose here such an approach by developing what we call the Quantum Thermodynamics Computational Engine (QTCE). In QTCE, the imaginary-time direction is discretized and the interaction is accounted for via a quantum cumulant expansion, where the coefficients are expressed in terms of noninteracting expectation values. The aim of QTCE is to enable the systematic resolution of interaction effects at fixed temporal discretization, as in lattice Monte Carlo calculations, but here in an algebraic rather than numerical fashion. Using this approach, in combination with numerical integration techniques (both known and alternative ones proposed here), we explore the thermodynamics of spin-1/2 fermions, focusing on the unitary limit in 3 spatial dimensions, but also exploring the effects of continuously varying the spatial dimension below 3. We find that, remarkably, extremely coarse temporal lattices, when suitably renormalized using known results from the virial expansion, yield stable partial sums for QTCE's cumulant expansion which are qualitatively and quantitatively correct in wide regions, compared with known experimental results.
↳ cond-mat.quant-gasnucl-thPhil.Trans.Roy.Soc.Lond.A(2024)·1 citation
08
K Isomers in Transuranium Nuclei
Fritz Peter Heßberger
K isomers in transuranium nuclei have become a most interesting subject in nuclear structure investigation in many laboratories within the recent twenty years. In this paper an overview on the present day situation will be given. It will focus on the conditions for occuring of this kind of isomers, their decay properties and systematics in their properties as far as experimental data are available.
↳ nucl-exnucl-th7 citations

Affiliations

first authorsco-authorsvia INSPIRE