All-photonic Entanglement Swapping with Remote Quantum Dots Demonstrates Deterministic Operation for Scalable Networks
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Entanglement swapping, a crucial process for extending the range of quantum communication, typically relies on creating connections between particles that initially have no relationship to each other. Mattia Beccaceci, Giuseppe Ronco, and Fabrizio Cienzo, working at Sapienza Università di Roma with colleagues, now demonstrate a fully photonic version of this swapping process using quantum dots, achieving a significant step towards practical quantum networks. Their experiment overcomes a key limitation of previous approaches, which relied on unpredictable, probabilistic light sources, by employing deterministic quantum dots embedded in innovative devices.
The team achieves a high fidelity of 0. 71, clearly exceeding the threshold for quantum behaviour, and their results, supported by a detailed theoretical model, pave the way for utilising these solid-state photon sources in future quantum repeater networks, promising more reliable and efficient long-distance quantum communication.
Deterministic Entanglement Between Distant Quantum Dots This research details the successful demonstration of deterministic entanglement between two distant quantum dots at room temperature. Scientists achieved this by creating entangled photon pairs from two separate quantum dots, and then verifying high-fidelity Bell state measurement and Hong-Ou-Mandel interference. This deterministic entanglement, reliably created rather than relying on chance, is a significant step towards practical quantum communication networks, operating at telecom wavelengths ideal for long-distance transmission. The experiment involved sophisticated techniques, including cryogenic cooling to temperatures of 3. 5 K and 5 K, and an optical setup utilizing back-reflection geometry with aspheric lenses and a Ti:Sapphire laser. Polarization control was achieved with half-wave plates and polarizers, and single-photon detection relied on superconducting nanowire detectors with fast timing. Coincidence counting with ultra-fast electronics verified photon correlations, while Hong-Ou-Mandel interference confirmed photon indistinguishability and Bell state measurement characterized the entangled state.
Deterministic Quantum State Swapping with Quantum Dots This study demonstrates all-photonic quantum state swapping using photon pairs emitted from two separate gallium arsenide quantum dots, a crucial step towards building scalable quantum networks. Researchers engineered a system where these quantum dots, deterministically embedded in hybrid semiconductor-piezoelectric devices, generate photons with nearly identical properties, essential for successful swapping. This deterministic approach overcomes limitations of previous probabilistic methods, paving the way for more reliable network components. To achieve this, the team hosted the quantum dots at cryogenic temperatures, 3. 5 K and 5 K respectively, within independent closed-cycle cryostats. Excitation and collection of photons occurred in a back-reflection geometry using a 0. 5-NA aspheric lens, focusing the pump laser and collecting the emitted signal. A Ti:sapphire laser, providing 140 fs excitation pulses at 80MHz, was doubled and a 4f pulse slicer selected a narrow spectral component, minimizing optical Stark shift and preventing spectral overlap. Spectral filtering, based on reflection from Volume-Bragg Gratings, isolated specific transitions, directing the photons either to a Bell state measurement stage or to a quantum state tomography setup via optical fibers. The core of the swapping process involved a polarization-selective Bell state measurement setup, utilizing a 50:50 fiber beam splitter for Hong-Ou-Mandel interference. Four polarization beam splitters and quarter/half/quarter wave plate sequences corrected polarization rotations, directing photons to superconducting nanowire single-photon detectors with 15ps timing jitter and 2ps time resolution. Coincidence counts between detector outputs identified specific Bell states, serving as a gate for subsequent quantum state tomography.
The team achieved a swapping fidelity of 0. 71(2), exceeding the classical limit by more than ten standard deviations, demonstrating the viability of this approach for quantum communication networks.
Remote Entanglement Swapping with Quantum Dots Scientists have achieved a breakthrough in quantum networking by demonstrating all-photonic entanglement swapping between two independent, remote quantum emitters. This work establishes a crucial step towards building practical quantum repeater networks with deterministic entangled photon-pair sources. Experiments revealed successful swapping of entanglement with a fidelity as high as 0. 71(2), exceeding the classical limit by more than 10 standard deviations, confirming the generation of entangled photons from distinct quantum dots and their subsequent correlation through the swapping protocol.
The team measured visibilities of two-photon interference reaching 0. 43(1) and 0. 46(3), which improved to 0. 48(1) and 0. 51(3) after accounting for experimental imperfections. Further refinement through temporal post-selection, using a time window of 10 picoseconds, increased the visibilities to 0. 66(1) and 0. 61(1), demonstrating the potential for enhanced performance. The fidelity of the swapped entanglement reached 0. 60(1) for one Bell state and 0. 56(1) for another, even without temporal post-selection. Remarkably, the team also demonstrated entanglement swapping on a different set of photons, achieving fidelities of 0. 62(2) and 0. 63(2). A theoretical model accurately predicts the observed swapping densities without requiring any fitting parameters, incorporating the measured lifetimes, fine structure splitting, and HOM visibilities of the quantum dots. The experimental data closely match the model’s predictions, confirming the accuracy of the theoretical framework. Measurements of swapping rates reached a few Hertz, corresponding to a probability of establishing entanglement between uncorrelated photons of approximately 2x 10 -5. This work delivers a significant advancement in quantum communication, paving the way for future developments in long-distance quantum networks.
Deterministic Entanglement Swapping in Quantum Dots This work demonstrates a significant advance in quantum networking through the successful implementation of all-photonic entanglement swapping between two independent quantum dot emitters. Researchers achieved this by generating entangled photon pairs from separate semiconductor structures and then using a beam splitter to create entanglement between photons that were initially uncorrelated. The experiment yielded a swapping fidelity of 0. 71, clearly exceeding the classical limit and demonstrating a high. 👉 More information 🗞 All-photonic entanglement swapping with remote quantum dots 🧠 ArXiv: https://arxiv.org/abs/2512.10651 Tags: