Surface plasma waves on metals arise from the collective oscillation of many free electrons in unison. These waves are usually quantized by direct analogy to electromagnetic fields in free space1, 2, 3, with the surface plasmon, the quantum of the surface plasma wave, playing the same role as the photon. It follows that surface plasmons should exhibit all the same quantum phenomena that photons do. Here, we report a plasmonic version of the Hong–Ou–Mandel experiment4, in which we observe unambiguous two-photon quantum interference between plasmons, confirming that surface plasmons faithfully reproduce this effect with the same visibility and mutual coherence time, to within measurement error, as in the photonic case. These properties are important if plasmonic devices are to be employed in quantum information applications5, which typically require indistinguishable particles.
At a glance
- Photon interactions at a rough metal surface. Phys. Rev. B 4, 4129–4138 (1971). &
- Single-photon excitation of surface plasmon polaritons. Phys. Rev. Lett. 101, 190504 (2008). et al.
- Quantum theory of surface-plasmon polariton scattering. Phys. Rev. A 82, 012325 (2010). , &
- Measurement of subpicosecond time intervals between two photons by interference. Phys. Rev. Lett. 59, 2044–2046 (1987). , &
- Quantum optics with surface plasmons. Phys. Rev. Lett. 97, 053002 (2006). , , &
- Generation of single optical plasmons in metallic nanowires coupled to quantum dots. Nature 450, 402–406 (2007). et al.
- Wave–particle duality of single surface plasmon polaritons. Nature Phys. 5, 470–474 (2009). et al.
- On-chip single plasmon detection. Nano Lett. 10, 661–664 (2010). et al.
- Quantum statistics of surface plasmon polaritons in metallic stripe waveguides. Nano Lett. 12, 2504–2508 (2012). et al.
- Plasmon-assisted transmission of entangled photons. Nature 418, 304–306 (2002). , &
- Energy–time entanglement preservation in plasmon-assisted light transmission. Phys. Rev. Lett. 94, 110501 (2005). et al.
- Quantum superposition and entanglement of mesoscopic plasmons. New J. Phys. 8, 13 (2006). , , &
- Demonstration of quadrature-squeezed surface plasmons in a gold waveguide. Phys. Rev. Lett. 102, 246802 (2009). et al.
- Silica-on-silicon waveguide quantum circuits. Science 320, 646–649 (2008). , , , &
- Derivation of reciprocity relations for a beam splitter from energy balance. Am. J. Phys. 57, 66–67 (1989). &
- Fourth-order interference technique for determining the coherence time of a light beam. J. Opt. Soc. Am. B 6, 100–103 (1989). , , &
- Plasmon assisted transmission of single photon wavepacket. Metamaterials 1, 106–109 (2007). , , , &
- Hong–Ou–Mandel interference mediated by the magnetic plasmon waves in a three-dimensional optical metamaterial. Opt. Express 20, 5213–5218 (2012). et al.
- Preservation of photon indistinguishability after transmission through surface-plasmon-polariton waveguide. Opt. Lett. 37, 1535–1537 (2012). et al.
- Quantum interference in plasmonic circuits. Nature Nanotech. 8, 719–722 (2013). , &
- Low loss mode size converter from 0.3 µm square Si wire waveguides to singlemode fibres. Electron. Lett. 38, 1669–1670 (2002). , , , &
- Efficient coupling between dielectric-loaded plasmonic and silicon photonic waveguides. Nano Lett. 10, 4851–4857 (2010). , , , &
- Quantum optics of lossy beam splitters. Phys. Rev. A 57, 2134–2145 (1998). , , &
- Supplementary information (492 KB)