Kelin Wang

Numerically exact solution to the finite-size Dicke model

By using extended bosonic coherent states, a new technique to solve the Dicke model exactly is proposed in the numerical sense. The accessible system size is two orders of magnitude higher than that reported in literature. Finite-size scaling for several observables, such as the ground-state energy, Berry phase, and concurrence are analyzed. The existing discrepancy for the scaling exponent of the concurrence is reconciled.

Quantum phase transition in the sub-Ohmic spin-boson model: An extended coherent-state approach

We propose a general extended coherent state approach to the qubit (or fermion) and multimode boson coupling systems. The application to the spin-boson model with the discretization of a bosonic bath with arbitrary continuous spectral density is described in detail, and very accurate solutions can be obtained. The quantum phase transition in the nontrivial sub-Ohmic case can be located by the fidelity and the order-parameter critical exponents for the bath exponents

Efficient construction of two-dimensional cluster states with probabilistic quantum gates

sl1/2

High-dimensional Virasoro integrable models and exact solutions

can be correctly given by the fidelity susceptibility, demonstrating the strength of the approach.

Exact solutions for some nonlinear equations

We propose an efficient scheme for constructing arbitrary two-dimensional (2D) cluster states using probabilistic entangling quantum gates. In our scheme, the 2D cluster state is constructed with starlike basic units generated from 1D cluster chains. By applying parallel operations, the process of generating 2D (or higher-dimensional) cluster states is significantly accelerated, which provides an efficient way to implement realistic one-way quantum computers.

Exact solutions to the Jaynes-Cummings model without the rotating-wave approximation

Abstract In this Letter, some Virasoro integrable models are obtained by means of the realizations of the generalized centerless Virasoro type symmetry algebra, [σ(f 1 ),σ(f 2 )]=σ( f 2 f 1 − f 1 f 2 ) . Two of them are (3+1)-dimensional extensions of the Nizhnik–Novikov–Veselov equation and breaking soliton equation. Some special type of high-dimensional soliton solutions like the camber solitons, multiple ring solitons and multiple dromion solutions for the breaking soliton equation is discussed. The interaction between two ring solitons is completely elastic. Whether the method can be used to find some (3+1)-dimensional models integrable by the inverse scattering transformation remains still open.

Exact solution for the motion of a particle in a Paul trap

Abstract Here we give a certain type of exact solutions for some nonlinear equations which describe well known nonlinear systems with background interaction.

A concise approach to the calculation of the polaron ground-state energy

By using tunable extended bosonic coherent states, the JC model without the rotating-wave approximation can be mapped to a polynomial equation with a single variable. The solutions to this polynomial equation recover exactly all eigenvalues and eigenfunctions of the model for all coupling strengths and detunings, which can be readily applied to recent circuit quantum electrodynamic systems operating in the ultra-strong coupling regime.

Optimal quantum cloning via spin networks

Abstract The motion of a particle in a time-dependent potential V ( x, t )=1/2[ U + V cos( ωt )] x 2 in a Paul trap can be described exactly by using a function series expansion to solve the corresponding Schrodinger equation. The validity of our approach is discussed and some physically meaningful results are shown.

Polaronic effect on the binding energy of an impurity with varying position in parabolic quantum dots

Abstract A new concise method is presented for the calculation of the polaron ground-state energy for a wide range of the coupling constant. The calculated results are in good agreement with the recent Monte Carlo ones. In the weak-coupling limit the energy expansion is very close to the sixth-order perturbative result.