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Multiple‐qubit logic gates, as an essential part of quantum logic gates, have wide practical application in quantum computation. Here, a scheme to directly construct a multiple‐qubit logic gate CkUm${\rm C}_{k}{\rm U}^{m}$, in which k control atoms apply an universal operation U on each of m target qubits in the Rydberg atom system is proposed. The scheme, based on Rydberg blockade and geometric quantum operations as well as optimized control theory, can greatly reduce the qubit number and the operation steps, improving the speed and robustness of the gating compared to the conventional multiple‐qubit gates consisting of single‐ and two‐qubit gates. Taking the C2U2 gate as an example, the performance of the proposal is numerically evaluated in terms of the fidelity of the quantum gate as well as the robustness against the static systematic errors and spontaneous emission. This work may provide a significative reference for constructing universal multiple‐qubit logic gates in future Rydberg atom experiments. [ABSTRACT FROM AUTHOR]

Since quantum entanglement plays a crucial role in quantum information processing, analyzing entangled states is indispensable for practical applications. Here a simple and direct protocol to distinguish arbitrary N‐qubit Greenberger–Horne–Zeilinger (GHZ) states by novel nonadiabatic noncyclic geometric quantum computation using Rydberg atoms is put forward. The Bell states can also be distinguished completely using this way. The protocol is justified by numerical simulation for Bell states and N‐qubit GHZ states, which evaluates the robustness and shows gratifying results. In addition, the idea is flexible, that is, available in any platform. Due to its simplicity and easy operation, the scheme would be very useful in quantum information science both theoretically and experimentally. [ABSTRACT FROM AUTHOR]

A scheme to prepare a 3D entangled state between a pair of Rydberg atoms via dissipative dynamics and electromagnetic induced transparency associated with the single‐atom dark state is proposed. The prepared entangled state is the dark state of the whole system. The scheme is also feasible regardless of initial purity or mixed state. Since the proposed scheme is based on the Rydberg block regime, the Rydberg–Rydberg interaction strength does not need to satisfy a certain relation with laser detuning, which is very different to the Rydberg‐antiblock‐based dissipative schemes. One group of Rydberg states and corresponding parameters to simulate the fidelity are used, which verify the feasibility of the scheme. [ABSTRACT FROM AUTHOR]