Instability of steady-state mixed symmetry-protected topological order to strong-to-weak spontaneous symmetry breaking
Abstract: We address the question of whether open quantum system dynamics which host mixed symmetry-protected topological (SPT) states as steady states continue to do so after introducing symmetric perturbations. In particular, we discuss the characteristics of the decohered cluster state --- a mixed SPT protected by a combined strong and weak symmetry --- and construct a parent Lindbladian which hosts it as a steady state. The parent Lindbladian can be mapped onto reaction-diffusion dynamics, which is exactly solvable, even in the presence of certain perturbations.
Order-by-disorder in the antiferromagnetic J1-J2-J3 transverse-field Ising model on the ruby lattice
Abstract: Extensively degenerate ground-state spaces due to frustration pose a formidable resource for emergent quantum phenomena. Perturbing extensively degenerate ground-state spaces may result in several distinct scenarios lifting the ground-state degeneracy. First, an infinitesimal perturbation can lead to a symmetry-broken order (order-by-disorder) or second the perturbation can result in a symmetry-unbroken phase (disorder-by-disorder), which can be either trivial or an exotic quantum spin liquid.
Scaling Law of Quantum Confinement in Single-Walled Carbon Nanotubes
Abstract: Quantum confinement significantly influences the excited states of sub-10 nm single-walled carbon nanotubes (SWCNTs), crucial for advancements in transistor technology and the development of novel opto-electronic materials such as fluorescent ultrashort nanotubes (FUNs). However, the length dependence of this effect in ultrashort SWCNTs is not yet fully understood in the context of the SWCNT exciton states.
Entangling four logical qubits beyond break-even in a nonlocal code
Abstract: Quantum error correction protects logical quantum information against environmental decoherence by encoding logical qubits into entangled states of physical qubits. One of the most important near-term challenges in building a scalable quantum computer is to reach the break-even point, where logical quantum circuits on error-corrected qubits achieve higher fidelity than equivalent circuits on uncorrected physical qubits.
A quantum monomer-dimer model on a Penrose tiling
Abstract: We define a quantum monomer-dimer model on a Penrose tiling (a quasicrystal) in the space of maximal dimer coverings. Monomers are necessarily present because it was shown by F. Flicker et al., PRX 10, 011005 (2020) that there are no perfect dimer coverings of Penrose tilings. Despite the presence of a finite density of monomers, our model has a Rokhsar-Kivelson (RK) point at which the ground state is a uniform superposition of all maximal dimer coverings.
A DMRG Study of Excitons in the 2D t-J Model
Abstract: Antiferromagnetic materials with microscopic behavior resembling that of the Fermi-Hubbard model are expected to host excitons, or bound electron-hole pairs. In order to investigate such behavior, we have optimized states of the t-J model in the single-particle-single-hole sector using the density matrix renormalization group (DMRG).
Electron-Photon Exchange-Correlation Functional in the Weak and Strong Light–Matter Coupling Regimes
Abstract: The intersection of quantum electrodynamics (QED) and density-functional theory (DFT) has opened up exciting opportunities in controlling quantum matter through light-matter coupling. This frontier, however, is beset with computational challenges, especially in the weak and strong coupling regimes. Building upon previous research, we present the results of nonperturbative QED functional in the long-wavelength limit, centered solely on the matter Hilbert space.
Towards Experimental Realization of Topological Floquet Models in Circuit QED
Abstract: Topological band structures are well known to produce symmetry-protected chiral edge states which transport particles unidirectionally. These same effects can be harnessed in the frequency domain using a spin-1/2 system subject to periodic drives.
Reducing circuit depth of commuting Pauli Strings diagonalization
Abstract: A variety of quantum algorithms employ Pauli operators as a convenient basis for studying the spectrum or evolution of Hamiltonians or measuring multibody observables. One strategy to reduce circuit depth in such algorithms involves simultaneous diagonalization of Pauli operators generating unitary evolution operators or observables of interest. We propose an algorithm yielding quantum circuits with depths O(nlogr) diagonalizing n-qubit operators generated by r Pauli operators.
Photon-Mediated Interactions in Lattices of Coplanar Waveguide Resonators
Abstract: Circuit quantum electrodynamics (circuit QED) has become one of the main platforms for quantum simulation and computation. One of its notable advantages is its ability to facilitate the study of new regimes of light-matter interactions. This is achieved due to the native strong coupling between superconducting qubits and microwave resonators, and the ability to lithographically define a large variety of resonant microwave structures, for example, photonic crystals.