In 2020 the polarization state of a single photon was teleported onto a single surface plasmon polariton (SPP) — a collective excitation of roughly 10610^6 electrons at a metal–dielectric interface — with average state fidelity 0.889±0.0040.889\pm 0.004 and process fidelity 0.820±0.0050.820\pm 0.005, both above the classical limit, establishing that teleportation can enter a plasmonic system. That experiment left open how far the approach extends: to entangled, multi-qubit, or higher-dimensional states, to teleportation of quantum gates, and ultimately to teleportation-based quantum computation with plasmonic systems, under the constraints of propagation loss, finite photon–plasmon–photon conversion efficiency, modulator extinction ratio, and fabrication quality. As of 2026 no experimental extension beyond the single-qubit polarization transfer exists; the only follow-ups inside the paradigm are theoretical proposals for continuous-variable teleportation in microwave-driven plasmonic graphene waveguides, while experimental quantum plasmonics has advanced other protocols such as random-number generation and sensing. The open problem is to extend SPP-mediated teleportation to more complex quantum-information tasks — in the framing of the source experiment, quantum teleportation of quantum gates and teleportation-based quantum computation with plasmonic systems — under the constraints that propagation loss and component imperfections impose on such protocols.

Background

A surface plasmon polariton (SPP) is a collective oscillation of free electrons coupled to an electromagnetic wave, propagating along a metal–dielectric interface; it confines light to subwavelength dimensions far below the diffraction limit, but suffers ohmic (propagation) loss. Quantum plasmonics studies whether such collective, lossy modes can carry genuine quantum information. The foundational demonstrations were: preservation of photon entanglement through plasmon-assisted transmission (Altewischer, van Exter and Woerdman, 2002); wave–particle duality of a single plasmon emitted by a nitrogen-vacancy center in a metallic nanowire (Kolesov et al., 2009); quantum statistics of two plasmons in metallic stripe waveguides, including fermion-like anti-bunching on a lossy channel (Di Martino et al., 2012); high-visibility quantum interference in plasmonic circuits (Heeres, Kouwenhoven and Zwiller, 2013) and the plasmonic Hong–Ou–Mandel effect, the two-plasmon analogue of photon bunching on a beam splitter (Di Martino et al., 2014). These established single- and two-plasmon quantum behavior, but no advanced quantum-information protocol — a status reviewed in Tame et al., 'Quantum plasmonics' (2013).

Quantum teleportation transfers an unknown quantum state using a shared entangled pair: the sender performs a Bell-state measurement (BSM, a joint projection onto a maximally entangled basis of the two received systems) and communicates the classical outcome; the receiver applies a conditional correction (active feed-forward). For qubit states, any measure-and-prepare strategy without entanglement is bounded to average fidelity 2/32/3, so fidelities above this certify quantum teleportation; quantum process tomography (reconstructing the full input–output map) similarly certifies the channel. Gate teleportation, introduced by Gottesman and Chuang (1999), implements a quantum logic gate by teleporting a state through a specially prepared entangled resource, and underlies teleportation-based models of universal quantum computation.

Jiang et al. (2020, Scientific Reports 10, 11503) realized the first — and so far only — teleportation involving a plasmonic system: using polarization-entangled photon pairs, coherent photon–plasmon–photon conversion on a metallic subwavelength hole array, a complete BSM, and active feed-forward with electro-optic modulators (EOMs), they teleported arbitrary polarization qubits from a photon to an SPP with the fidelities above. The price of the plasmonic channel is loss: the conversion and propagation losses reduce the coincidence count rate so much that very long integration times were required, and the SPP-channel fidelity fell below the all-optical case, attributed to the low extinction ratio (contrast) of the feed-forward EOMs rather than to a fundamental plasmonic decoherence. The authors explicitly frame their result as a first feasibility step toward more complicated protocols — teleportation of quantum gates and teleportation-based quantum computation with plasmonic systems — whose realization depends on further experimental advances. Whether SPP-mediated teleportation can actually be scaled to such tasks, and what loss and imperfection bounds it faces, is the unresolved question.

Problem Statement

Plasmon-mediated quantum teleportation has been experimentally demonstrated only for the polarization state of a single photon teleported to a single surface plasmon polariton (Jiang et al. 2020), with the loss budget and feed-forward imperfections already degrading rate and fidelity. The open problem, as posed by that work, is to realize more complicated quantum-information protocols with plasmonic systems, beyond the single-qubit polarization transfer.

Concretely: realize quantum teleportation through a plasmonic channel of quantum-information objects beyond the single-qubit polarization state — for example entangled or multi-qubit states, higher-dimensional states, or the teleportation of quantum gate operations (gate teleportation in the sense of Gottesman and Chuang), as a step toward teleportation-based quantum computation with plasmonic systems — and verify the quantum nature of the transfer at fidelities above the appropriate classical bounds. The 2020 demonstration achieved the single-qubit case with entangled photon pairs, complete Bell-state measurements, and active feed-forward via electro-optic modulators; extensions may follow this discrete-variable architecture or other teleportation protocols (the continuous-variable plasmonic proposals described in the opening paragraph belong to the same paradigm).

The extension must contend with the loss budget of the plasmonic channel: the achievable fidelity and usable event (coincidence) rate of any such protocol depend on the number of plasmonic elements, SPP propagation loss, photon–plasmon–photon conversion efficiency, modulator extinction ratio, and fabrication quality, and these constraints determine the experimentally achievable conditions under which plasmonic teleportation can be extended.

A complete answer demonstrates that the plasmonic system (a collective excitation of roughly 10610^6 electrons) can carry a quantum-information task beyond a single qubit — one whose capability is not obtainable by independent single-qubit transfers, for instance entangling-gate teleportation in the Gottesman-Chuang sense or teleportation of a genuinely multi-partite or higher-dimensional entangled state — verified above the appropriate classical fidelity bound, under experimentally achievable loss and component-quality conditions.

References

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