We have studied the two-qubit quantum Rabi model in asymmetric case and its generalizations with dipole Heisenberg-type qubit-qubit interactions. The solutions are obtained analytically eigenstates given terms of extended coherent states or photon number states. For identical qubit-photon couplings, a novel type quasi-exact solution which exists for all coupling values constant eigenenergy is found, leading to level crossings within same parity subspace even non-identical qubits. In contrast...

We prove, by means of a unified treatment, that the superradiant phase transitions Dicke and classical oscillator limits simple light-matter models are indeed same type. show mean-field approximation is exact in both cases, compute structure location parameter space. extend this study to fuller range models, paying special attention symmetry considerations. uncover general features space parameters these models.

General solutions to the quantum Rabi model involve subspaces with an unbounded number of photons. However, for multiqubit multimode case, we find special at most one photon arbitrary qubits and modes. Such exist single qubit-photon coupling strength constant eigenenergy, while still being entangled states. Taking advantage their peculiarities reach ultrastrong regime, propose adiabatic scheme fast deterministic generation a two-qubit Bell state single-photon $W$ states nonadiabatic error...

An efficient method is developed for multiband simulation of quantum transport in nanowire electronic devices within nonequilibrium Green's function formalism. The efficiency relies on a model order reduction technique, which projects the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k · p</i> Hamiltonian into much smaller subspace constructed by sampling Bloch modes each cross-section layer. Several approaches are discussed to obtain minimum...

As a kind of toxic gas, carbon monoxide (CO) can hinder uptake oxygen in humans. However, more and studies have shown that CO is an important gaseous messenger the body playing indispensable role intracellular signaling pathways. So, it necessary to develop analytical method study living organisms. Although there are many CO-responsive probes, most them disadvantages small Stokes shift or short emission wavelength. In order address above issue, novel probe (FDX-CO) with large (190 nm) long...

We propose a unified and deterministic scheme to generate arbitrary single-photon multimode $W$ states in circuit QED. A three-level system (qutrit) is driven by pump-laser pulse coupled $N$ spatially separated resonators. The coupling strength for each spatial mode $g_i$ totally decide the generated N-mode state $\vert W_N \rangle=\frac{1}{A}\sum_{i=1}^N g_i|0_1 0_2 \cdots 1_i 0_{i+1}\cdots 0_N\rangle$, so \rangle$ can be just tuning $g_i$. could not only inside resonators but also release...

The simplified two-qubit Rabi model is proposed and its analytical solution presented. There are no level crossings in the spectral graph of model, which indicates that it not integrable. criterion integrability for by Braak (2011 Phys. Rev. Lett. 107 100401) also used same conclusion, consistent with what shows, can be drawn, remains valid when applied to case. another example a non-integrable but exactly solvable system except generalized model.

There are well-known dark states in the even-qubit Dicke models, which products of two-qubit singlets and a Fock state, where qubits decoupled from photon field. These spin can be used to store quantum correlations since they preserve entanglement even under dissipation, driving dipole-dipole interactions. One features for these is that their eigenenergies independent qubitphoton coupling strength. We have obtained novel kind dark-like multi-qubit multi-photon Rabi whose also constant whole...

We present an analog version of the quantum approximate optimization algorithm suitable for current annealers. The central idea this is to optimize schedule function, which defines adiabatic evolution. It achieved by choosing a parametrization function based on interpolation methods fixed time, with potential generate any function. This provides result problems that may be developed during coherence time annealers their way toward advantage.

In this work, we simulate a realistic junctionless (JL) field-effect transistor using multi-scale approach. Our approach features combination of the first-principles atomistic calculation, semi-classical semiconductor device simulation, compact model generation, and circuit simulation. The transfer characteristics JL transistors are simulated by recently developed quantum mechanical/electromagnetics method, good agreement is obtained compared to experiment. A for then generated subsequent We...

We have found the algebraic structure of two-qubit quantum Rabi model behind possibility its novel quasi-exact solutions with finite photon numbers by analyzing Hamiltonian in number space.The eigenstates at most 1 exist whole qubit-photon coupling regime constant eigenenergy equal to single energy ω, which can be clear demonstrated from structure.With similar method, we find these special "dark states"-like commonly for Jaynes-Cummings model, E = N ω (N -1, 0, 1, . ..), and one them is also...

We propose that the evolution of superfluidity from Bardeen-Cooper-Schrieffer (BCS) regime to Bose-Einstein condensation (BEC) can be realized using ultracold Fermi gas coupled a single-mode cavity. By functional integral formalism, we derive an effective atom-only action, which mimics two-component with tunable two-body interaction. First, address features cavity-mediated find matter-light coupling creates $s$-wave scattering whose sign and amplitude are controlled by parameters Second,...

We proposed and theoretically investigated a one-dimensional slotted photonic crystal nanofiber cavity (SPCNC) for complex refractive index sensing in gaseous environment. Three-dimensional finite-difference time-domain simulations show that high quality factor (Q) of 1.45×106 sensitivity 756 nm/refractive unit (RIU) can be simultaneously achieved the detection real part (RI) surrounding gas. In addition, we demonstrated SPCNC possesses capability detecting change imaginary RI. A 1525 nm/RIU...

We propose and theoretically investigate a novel one-dimensional photonic crystal nanocylinder cavity (PCNC) that can support the second-order transverse-electric-like (TE2 ) mode. Three-dimensional finite-difference time-domain simulations show TE2 mode of PCNC possesses an ultrahigh quality factor 1.22 × 108 small volume when is made high-index material silicon. For PCNCs which are low-index materials, corresponding factors modes reach highest values relative to previously demonstrated PhC...

We studied the two-qubit quantum Rabi model and found its dark state solutions with at most N photons. One peculiar case presents when $N=3$, which has constant eigenenergy in whole coupling regime leads to level crossings within same parity subspace. also discovered asymptotic $N=2i+3$ $(i=1,2,3,\dots)$ photons, $N\hbar \omega$ $g$ becomes much larger than photon frequency $\omega$. Although generally all number states are involved model, such $N$-photon exist may have applications...

Abstract We study the two-qubit asymmetric quantum Rabi model (AQRM) and find its dark-state solution. Such solutions have at most one photon constant eigenenergy in whole coupling regime, causing level crossings spectrum, although there is no explicit conserved quantity except for energy. an operator basis to label all degeneracies with eigenvalues, compare it well-known hidden symmetry which exists when bias parameter ϵ a multiple of half resonator frequency ω . Extended multimode case, we...

We propose a scheme for realizing deterministic two-photon C-Z gate based on variants of the quantum Rabi model, which is feasible within framework circuit QED. begin by utilizing interaction to implement nonlinear sign (NS) gate, and subsequently, we construct following KLM scheme. consider three different regimes: strong coupling regime, perturbative ultrastrong large detuning regime. Our results indicate that operates fast with high fidelity robust against decoherence, thereby offering...