Single-step multipartite entangled states generation from coupled circuit cavities

Abstract

Green-Horne-Zeilinger states are a typical type of multipartite entangled states, which plays a central role in quantum information processing. For the generation of multipartite entangled states, the single-step method is more preferable as the needed time will not increase with the increasing of the qubit number. However, this scenario has a strict requirement that all the two-qubit interaction strengths should be the same, or the generated state will be of low quality. Here, we propose a scheme for generating multipartite entangled states of superconducting qubits, from a coupled circuit cavities scenario, where we rigorously achieve the requirement via adding an extra z-direction ac classical field for each qubit, leading the individual qubit-cavity coupling strength to be tunable in a wide range, and thus can be tuned to the same value. Meanwhile, in order to obtain our wanted multi-qubits interaction, x-direction ac classical field for each qubit is also introduced. By selecting the appropriate parameters, we numerically shown that high-fidelity multi-qubit GHZ states can be generated. In addition, we also show that the coupled cavities scenario is better than a single cavity case. Therefore, our proposal represents a promising alternative for multipartite entangled states generation.

Implementing a multi-target-qubit controlled-not gate with logical qubits outside a decoherence-free subspace and its application in creating quantum entangled states

“…To date, GHZ states of 10 or more physical qubits have been experimentally demonstrated in various systems [60][61][62][63][64][65]. Theoretically, a large number of theoretical methods have been presented for creating GHZ states of multiple physical qubits with different kinds of quantum systems [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80]. However, how to prepare GHZ states with logical qubits encoded in DFS has rarely been investigated.…”

Fast Conversion of Three‐Particle Dicke States to Four‐Particle Dicke States with Rydberg Superatoms

“…In the last few years, many theoretical and experimental schemes for the generation of multipartite entangled states have been proposed. [ 1–10 ] Among these multiparticle entangled states, Dicke states have attracted a lot of attention due to their many advantages, such as entanglement characterization, [ 11–14 ] robustness to decoherence, [ 15 ] and permutational symmetry, which allows to simplify the task of state tomography. [ 16,17 ] Dicke states were first proposed by R. Dicke in 1954 [ 18 ] for describing light emission from a cloud of atoms, the m ‐qubit symmetric Dicke states with k excitations are defined as $$$$\begin{align} {\left|D_{m}^{(k)}\right\rangle} =\frac{1}{\sqrt {C_{m}^{k}}}\sum _{n}\hat{P}_{n}{\left|0^{\otimes (m-k)}1^{\otimes k}\right\rangle} ,(0\le k\le m) \end{align}$$$$where the sum is over all permutations with k qubits in the state $$|1\rangle$$ and $$\hat{P}_{n}$$ is permutation operator.…”

Transferring quantum entangled states between multiple single-photon-state qubits and coherent-state qubits in circuit QED

“…The new and rapidly growing field of circuit QED, consisting of microwave radiation fields and fixed artificial atoms, offers extremely exciting prospects for solid-state QIP [20][21][22][23][24][25][26][27][28]. In the following, we will present an approach to transfer the entangled state (1) between n SPS qubits and n CS qubits, in a circuit QED system that consists of 2n microwave cavities coupled to a superconducting flux qutrit.…”