en.Wedoany.com Reported - Researchers at the Duke Quantum Center and IonQ have demonstrated the distributed generation of Greenberger-Horne-Zeilinger (GHZ) states using individual trapped ions on a three-node quantum network. The experimental setup comprises three spatially separated hardware modules, each approximately 2 meters apart, connected via 3-meter single-mode optical fibers to a centralized free-space GHZ state generator. This network achieves remote three-party entanglement without requiring local two-qubit gates or post-selection protocols, establishing atomic state fidelities ranging from 0.841(17) to 0.881(17) at an entanglement generation rate of 0.095(5) s−1.
Each hardware node isolates a single 138Ba+ (barium) ion qubit confined in a four-rod Paul trap. A static magnetic field of 4.2446(2) G lifts the ground-state degeneracy, defining Zeeman qubit levels ∣↓⟩ and ∣↑⟩ with a splitting frequency of ω0=2π×11.8964(5) MHz. A 3-picosecond laser pulse simultaneously excites the ions, triggering a spontaneous emission sequence at 493 nm that generates entangled ion-photon states with an average fidelity of 0.983(1). The emitted single photons are transmitted via optical fiber networks to the centralized generator, where a waveplate array aligns their polarization to a shared horizontal/vertical basis before pairwise interference at polarization beam splitters. Triple coincidence detection on six avalanche photodiodes erases the photon "which-path" information, heralding the entangled state of the target atomic memories.
Analysis of system operational constraints indicates that the primary sources of state infidelity are polarization mixing (0.037) and spatial mode mismatch (<0.03). Motion decoherence induced by photon recoil within the 50-nanosecond heralding window contributes an additional 0.03 infidelity, while state preparation and measurement (SPAM) configurations introduce an error rate of 0.015. The net end-to-end single-photon collection efficiencies (pi) for the three nodes range from 0.0074 to 0.0145. These efficiency limitations are determined by fiber coupling drift and cumulative recoil heating over repeated 1-microsecond entanglement cycles, currently requiring periodic interruptions for Doppler cooling.
This three-node network performs a deterministic test of quantum nonlocality by measuring the Mermin parameter at 3.203(45), violating the classical local hidden variable upper bound of ≤2 by 27 standard deviations. Qubit states are analyzed by driving a 1762 nm laser π-pulse to transfer the ∣↓⟩ state population to the target 2D5/2 level, followed by fluorescence imaging under combined 493 nm and 650 nm illumination. Due to the high state readout efficiency (>99.7%) of trapped ions, the experiment closes the detection loophole. This represents a verification of multi-node Mermin inequality violation using remote, individually addressable atomic memories rather than purely photonic or ensemble media.
The realization of fully distributed three-party entanglement outlines an engineering pathway for modular quantum computing systems. This infrastructure model does not attempt to scale processing power within a single monolithic vacuum chamber; instead, it connects distinct localized quantum processing nodes via photonic interconnects to distribute computational workloads. The event-ready generation of these distributed states establishes a foundational framework for multi-party cryptographic protocols, secure quantum secret sharing, and distributed quantum sensing networks using interconnected atomic nodes.
This article is compiled by Wedoany. All AI citations must indicate the source as "Wedoany". If there is any infringement or other issues, please notify us promptly, and we will modify or delete it accordingly. Email: news@wedoany.com
