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Applied Physics Letters

Heralded and robust W-state generation for distant superconducting qubits with practical microwave pulse scattering

Z P Guo, Zhihao Xie, Yimin Wang, Zhenhua Li, Tao Li

Published Dec 25, 2023• 5 citations
Publisher

Abstract

Nonlocal multipartite entanglement holds significant potential for both fundamental physics and practical applications. We present a robust protocol for generating remote entanglement, specifically W states, among multiple nonlocal superconducting qubits. Our protocol employs practical microwave pulse scattering through a microwave cavity, which is coupled to a far-detuned superconducting transmon qubit, facilitating a CNOT-like operation. Our approach can be implemented without the need for single microwave-photon sources and its completion is heralded by microwave photon measurements. Furthermore, our protocol can generate faithful nonlocal W states of distant superconducting qubits with practical detector units, each cascading two quantum non-demolition detectors, rather than ideal single-photon detectors. These distinct features make our protocol particularly useful for large quantum secure communication networks.

DOI
10.1063/5.0189377

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Abstract We propose an efficient protocol for rapidly generating quantum entangled states between a transmon qubit and microwave photons via shortcuts to adiabaticity. For a dispersive coupling between the qubit and cavity mode, three composite qubit-photon states constitute our system. Two microwave drivings are applied to the three-level system, leading to a Λ-type interaction. Based on shortcut-like quantum state transfer, the maximally entangled states can be controllably generated in a non-adiabatic manner. We address the dependence of the needed time for generating entangled states on the Rabi couplings, and further analyse the robustness of quantum operations. The present scheme opens up an opportunity for fast creating entangled states of the superconducting qubit-cavity systems.
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On-demand creation of entanglement between distant qubits is a necessary ingredient for distributed quantum computation. We propose an entanglement scheme that allows for single-shot deterministic entanglement creation by detecting a single photon passing through a Mach–Zehnder interferometer with one transmon qubit in each arm. The entanglement production essentially relies on the fact that superconducting microwave structures allow one to achieve strong coupling between the qubit and the photon. By detecting the photon via a photon counter, a parity measurement is implemented and the wave function of the two qubits is projected onto a maximally entangled state. Most importantly, the entanglement generation is heralded such that our protocol is not susceptible to photon loss due to the indivisible nature of single photons.
Abstract Fast generation of entanglement states is of critical importance for robust quantum information processing. In this paper, we propose an efficient protocol for a rapidly generating entanglement state between a transmon qubit and microwave photons. The transmon system is coupled to a classical microwave driving and a quantized cavity mode. With the adjustable classical driving, we consider the entanglement creation by transferring the composite states via resonant driving. Compared with the non-resonant cases, the present operation can be accomplished in a shorter time, which thus contributes to mitigating the decoherence effects. Moreover, many transmons inside a common cavity field could be addressed in a scalable way. The proposed strategy could offer a promising approach to optimally prepare entanglement states with superconducting quantum systems.