Efficient Criteria of Quantumness for a Large System of Qubits

In order to model and evaluate large-scale quantum systems, e.g., quantum computer and quantum annealer, it is necessary to quantify the “quantumness” of such systems. In this paper, we discuss the dimensionless combinations of basic parameters of large, partially quantum coherent systems, which could be used to characterize their degree of quantumness. Based on analytical and numerical calculations, we suggest one such number for a system of qubits undergoing adiabatic evolution, i.e., the accessibility index. Applying it to the case of D-Wave One superconducting quantum annealing device, we find that its operation as described falls well within the quantum domain.

Mass Transfer and Stellar Evolution of the White Dwarfs in AM CVn Binaries

We calculate the stellar evolution of both white dwarfs (WDs) in AM CVn binaries with orbital periods of P orb ≈ 5–70 minutes. We focus on the cases where the donor starts as a M He < 0.2M ⊙ helium WD and the accretor is a M WD > 0.6 M ⊙ WD. Using Modules for Experiments in Stellar Astrophysics, we simultaneously evolve both WDs assuming conservative mass transfer and angular momentum loss from gravitational radiation. This self-consistent evolution yields important feedback of the properties of the donor on the mass-transfer rate, M ̇ , as well as the thermal evolution of the accreting WD. Consistent with earlier work, we find that the high M ̇ 's at early times forces an adiabatic evolution of the donor for P orb < 30 minutes so that its mass–radius relation depends primarily on its initial entropy. As the donor reaches M He ≈ 0.02–0.03 M ⊙ at P orb ≃ 30 minutes, it becomes fully convective and could lose entropy and expand much less than expected under further mass loss. However, we show that the lack of reliable opacities for the donor’s surface inhibit a secure prediction for this possible cooling. Our calculations capture the core heating that occurs during the first ≈107 yr of accretion and continue the evolution into the phase of WD cooling that follows. When compared to existing data for accreting WDs, as seen by Cheng and collaborators for isolated WDs, we also find that the accreting WDs are not as cool as we would expect given the amount of time they have had to cool.

Topological pumping in acoustic waveguide arrays with hopping modulation

Thouless pumping is the adiabatic transportation of quantized charge, which is regarded as the dynamic version of the quantum Hall effect. Here we propose the design of an acoustic system to demonstrate the topological pumping characterized by transporting acoustic energy from one side to the opposite. The system is composed of coupled acoustic waveguide arrays with modulated coupling along both cross-sections and the propagating direction. We explore multiple topological phases by introducing rich spatial frequency or enlarged range of the hopping modulation. Such distinct topological phases are evidenced by adiabatic evolution of the edge states, where the acoustic system varies continuously and slowly along the state propagating direction. The robustness behavior of the edge states transport is also verified with numerical simulations to imply their topology origin. Our work provides a route to realize topological phases and utilize the corresponding edge states in waveguide arrays that can lead to versatile acoustic wave manipulation applications.

A Review of Quintessential Inflation

Some of the most important quintessential inflation scenarios, such as the Peebles–Vilenkin model, are described in detail. These models are able to explain the early- and late-time accelerated expansions of our universe, and the phase transition from the end of inflation to the beginning of kination where the adiabatic evolution of the universe was broken in order to produce enough particles to reheat the universe with a viable temperature, thereby aligning with the Hot Big Bang universe. In addition, while considering the reheating to be due to the gravitational production of superheavy particles conformally coupled to gravity, we checked that the considered scenarios do not suffer problems due to the overproduction of gravitational waves at the end of inflation, and thus the validity of Big Bang nucleosynthesis is preserved.

Crystallographic interacting topological phases and equivariant cohomology: to assume or not to assume

For symmorphic crystalline interacting gapped systems we derive a classification under adiabatic evolution. This classification is complete for non-degenerate ground states. For the degenerate case we discuss some invariants given by equivariant characteristic classes. We do not assume an emergent relativistic field theory nor that phases form a topological spectrum. We also do not restrict to systems with short-range entanglement, stability against stacking with trivial systems nor assume the existence of quasi-particles as is done in SPT and SET classifications respectively. Using a slightly generalized Bloch decomposition and Grassmanians made out of ground state spaces, we show that the P-equivariant cohomology of a d-dimensional torus gives rise to different interacting phases, where P denotes the point group of the crystalline structure. We compare our results to bosonic symmorphic crystallographic SPT phases and to non-interacting fermionic crystallographic phases in class A. Finally we discuss the relation of our assumptions to those made for crystallographic SPT and SET phases.

Engineering Reflective Metasurfaces with Ising Hamiltonian and Quantum Annealing

<div><div><div><p>We present a novel and flexible method to optimize the phase response of reflective metasurfaces towards a desired scattering profile. The scattering power is expressed as a spin-chain Hamiltonian using the radar cross section formalism. For metasurfaces reflecting an oblique plane wave, an Ising Hamiltonian is obtained. Thereby, the problem of achieving the scattering profile is recast into finding the ground-state solution of the associated Ising Hamiltonian. To rapidly explore the configuration states, we encode the Ising coefficients with quantum annealing algorithms, taking advantage of the fact that the adiabatic evolution efficiently performs energy minimization in the Ising model. Finally, the optimization problem is solved on the D-Wave 2048-qubit quantum adiabatic optimizer machine for binary phase as well as quadriphase reflective metasurfaces. Even though the work is focused on the phase modulation of metasurfaces, we believe this approach paves the way to fast optimization of reconfigurable intelligent surfaces that are mod- ulated in both amplitude and phase for multi-beam generation in and beyond 5G/6G mobile networks.</p></div></div></div>

Engineering Reflective Metasurfaces with Ising Hamiltonian and Quantum Annealing

<div><div><div><p>We present a novel and flexible method to optimize the phase response of reflective metasurfaces towards a desired scattering profile. The scattering power is expressed as a spin-chain Hamiltonian using the radar cross section formalism. For metasurfaces reflecting an oblique plane wave, an Ising Hamiltonian is obtained. Thereby, the problem of achieving the scattering profile is recast into finding the ground-state solution of the associated Ising Hamiltonian. To rapidly explore the configuration states, we encode the Ising coefficients with quantum annealing algorithms, taking advantage of the fact that the adiabatic evolution efficiently performs energy minimization in the Ising model. Finally, the optimization problem is solved on the D-Wave 2048-qubit quantum adiabatic optimizer machine for binary phase as well as quadriphase reflective metasurfaces. Even though the work is focused on the phase modulation of metasurfaces, we believe this approach paves the way to fast optimization of reconfigurable intelligent surfaces that are mod- ulated in both amplitude and phase for multi-beam generation in and beyond 5G/6G mobile networks.</p></div></div></div>