Multiparticle entanglement has important applications in quantum information and quantum computing. Here, we propose two schemes to fuse large-scale entangled W states and GHZ states. In the first fusion scheme, we send two Rydberg superatoms that belong to an n particle W state and an m particle W state, respectively, into a vacuum cavity; an ( n + m −2) particle W state can be obtained by detecting the state of the superatoms after the interaction. In the second fusion scheme, we send two Rydberg superatoms into two separate cavities; with the assistance of a circularly polarized photon, we can obtain a ( k + l ) particle GHZ state after detecting the state of the photon. The numerical simulation analysis shows that both schemes are robust against the spontaneous emission of superatoms and the decay of the cavity. The feasibility analysis indicates that these two schemes can be realized in experiments.
Multiparticle entanglement has important applications in quantum information and quantum computing. Here, we propose two schemes to fuse large-scale entangled W states and GHZ states. In the first fusion scheme, we send two Rydberg superatoms that belong to an n particle W state and an m particle W state, respectively, into a vacuum cavity; an ( n + m −2) particle W state can be obtained by detecting the state of the superatoms after the interaction. In the second fusion scheme, we send two Rydberg superatoms into two separate cavities; with the assistance of a circularly polarized photon, we can obtain a ( k + l ) particle GHZ state after detecting the state of the photon. The numerical simulation analysis shows that both schemes are robust against the spontaneous emission of superatoms and the decay of the cavity. The feasibility analysis indicates that these two schemes can be realized in experiments.
Abstract Quantum entanglement is the basic resource of quantum information processing and quantum computation, especially multi-partite entanglement. The simple and efficient generation of multi-partite entanglement has always been one of the hot topics of scholars. In this paper, we propose a qubit-loss-free fusion scheme for generation of large-scale entangled W states with Rydberg superatom. By sending two superatoms belonging to a k -atom W states and a l -atom W states, respectively, into a cavity, we may obtain a ( k + l )-atom W states via detecting the cavity state after interaction. The numerical simulation analysis shows that the fidelity is robust against both spontaneous emission of superatoms and decay of the cavity. In addition, the feasibility analysis indicates this scheme can also be realized in experiment.
Abstract Quantum entanglement is playing an increasingly crucial role in the field of quantum information. The conversion between different types of entangled states, especially for GHZ state and W state, can greatly enhance the efficiency of quantum information processing. Here, a two‐step scheme is proposed to realize the conversion between GHZ state and W state with Rydberg superatoms, in which the collective states of superatom are used to encode quantum information. In the first step, let a single‐photon pulse pass through two cavities that trap superatoms in sequence and detect the state of photon to complete this task. In the second step, shortcuts are employed to adiabaticity based on superadiabatic technique and design appropriate Rabi frequencies for the system. The numerical simulations demonstrate that this scheme possesses a high fidelity and exhibits robustness against detrimental effects such as atomic spontaneous emission, cavity losses, fiber photon leakages and noise. Furthermore, the intricate pulses within this scheme are decomposed into a linear superposition of Gaussian pulses, enhancing experimental feasibility. Finally, the scheme is extended to deal with the scenario of multi‐superatom. This method provides a way to convert other types of entangled states.
We propose a scheme for preparation of large-scale entangled W states based on the fusion mechanism via quantum Zeno dynamics. By sending two atoms belonging to an n-atom W state and an m-atom W state, respectively, into a vacuum cavity (or two separate cavities), we may obtain a (n + m - 2)-atom W state via detecting the two-atom state after interaction. The present scheme is robust against both spontaneous emission of atoms and decay of cavity, and the feasibility analysis indicates that it can also be realized in experiment.
The W state, as a robust multipartite entangled state, plays an important role in quantum information processing, quantum network construction and quantum computing. In this paper, a three-level ladder-type Rydberg atomic system is placed into a Rydberg blocking sphere to form a superatom. Each superatom has many collective states including just one Rydberg excitation constrained by the Rydberg blockade effect. In the weak cavity field limit, at most one atom can be pumped into excited state, then we can describe the superatom by using a three-level ladder-type system. Afterwards we encode quantum information about the effective energy levels of Rydberg superatoms and propose a fast scheme for preparing the Rydberg superatom W state based on the superadiabatic iterative technique and quantum Zeno dynamics.This scheme can be achieved in only one step by controlling the laser pulses. In this scheme, the superatoms are trapped in spatially separated cavities connected by optical fibers, thereby greatly improving the feasibility of experimental manipulation. A remarkable feature is that it does not need to accurately control experimental parameters and interaction time. Meanwhile, the form of counterdiabatic Hamiltonian is the same as that of the effective Hamiltonian. Through numerical simulations, the fidelity of this scheme can reach 99.94%. Even considering decoherence effects, including atomic spontaneous emission and photon leakage, the fidelity can still exceed 97.5%, thereby further demonstrating the strong robustness of the solution. In addition, the Rabi frequency can be characterized as a linear superposition of Gaussian functions, and this representation significantly alleviates the complexity encountered in practical experiments. Futhermore, we also analyze the influence of parameter fluctuations on the fidelity, and the results show that this scheme is robust against parameter fluctuations. Finally, the present scheme is extended to the case of N Rydberg superatoms, which shows the scalability of our scheme.
Entangled states are of significant importance in the realms of quantum communication and quantum information processing. Fusion technology has been proven as a viable method to prepare large-size entangled states from two or more small-size entangled states in a quantum electrodynamics (QED) system. However, most fusion schemes in QED systems require precise control over the evolution time, thereby amplifying the difficulty in the experiment. Therefore, it is of great importance to find a scheme to fuse entangled states in a QED system without requiring precise control over the evolution time. In this study, we propose a fusion scheme to efficiently prepare large-scale entangled states by transitionless quantum driving (TQD) with Rydberg superatoms. We position an ultracold ensemble of n individual ladder-type Rydberg atoms within the blockade sphere, thereby forming a superatom. Subsequently, we encode quantum information onto the collective state of the Rydberg superatoms. Through the combined use of quantum Zeno dynamics and TQD, the scheme enables the fast fusion of an m -qubits W (GHZ) state and an n -qubits W (GHZ) state into a ( m + n −2)-qubits W (GHZ) state without the requirement for precise control over the evolution time. Moreover, the impact of decoherence factors, operational imperfection, and noise on fidelity is taken into account. Numerical simulations suggest that the proposed method demonstrates high fidelity.
In this paper, we study how to fuse two W states into a larger W state in a cavity quantum electrodynamic system. Two atoms are collided within a detuned vacuum cavity mode. One atom is from the first N-atom W state system, and the other is from the second M-atom W state system. The two atoms will be detected after flying out of the cavity mode. If only one excitation is detected between the two atoms, an (N + M − 2)-atom W state can be generated with some probability. If no excitation is detected between the two atoms, the remaining (N − 1)-atom W state and (M − 1)-atom W state can be re-fused using the same procedure, continuing until two excitations are detected between the two atoms. Using this procedure, the chance of entanglement of the two W states is as large as possible. A feasibility analysis indicates that this scheme can be implemented using existing experimental technologies.