Forming the backbone of quantum technologies today, entanglement1, 2 has been demonstrated in physical systems as diverse as photons3, ions4 and superconducting circuits5. Although steadily pushing the boundary of the number of particles entangled, these experiments have remained in a two-dimensional space for each particle. Here we show the experimental generation of the first multi-photon entangled state where both the number of particles and dimensions are greater than two. Two photons in our state reside in a three-dimensional space, whereas the third lives in two dimensions. This asymmetric entanglement structure6 only appears in multiparticle entangled states with d > 26. Our method relies on combining two pairs of photons, high-dimensionally entangled in their orbital angular momentum7. In addition, we show how this state enables a new type of ‘layered’ quantum communication protocol. Entangled states such as these serve as a manifestation of the complex dance of correlations that can exist within quantum mechanics.
At a glance
- Die gegenwärtige situation in der quantenmechanik. Naturwissenschaften 23, 823–828 (1935).
- The present situation in quantum mechanics: a translation of Schrödinger's “Cat Paradox” paper. Proc. Am. Phil. Soc. 124, 323–338 (1980).
- Observation of eight-photon entanglement. Nature Photon. 6, 225–228 (2012). et al.
- Experimental violation of multipartite bell inequalities with trapped ions. Phys. Rev. Lett. 112, 100403 (2014). et al.
- State preservation by repetitive error detection in a superconducting quantum circuit. Nature 519, 66–69 (2015). et al.
- Structure of multidimensional entanglement in multipartite systems. Phys. Rev. Lett. 110, 030501 (2013). &
- Three-particle entanglements from two entangled pairs. Phys. Rev. Lett. 78, 3031–3034 (1997). , , &
- On the Einstein–Podolsky–Rosen paradox. Physics 1, 195–200 (1964).
- Proposed experiment to test local hidden-variable theories. Phys. Rev. Lett. 23, 880–884 (1969). , , &
- 69–72 (Kluwer, 1989). , & in Bell‘s Theorem, Quantum Theory, and Conceptions of the Universe (ed. Kafatos, M.)
- Extreme quantum entanglement in a superposition of macroscopically distinct states. Phys. Rev. Lett. 65, 1838–1840 (1990).
- Experimental test of quantum nonlocality in three-photon Greenberger–Horne–Zeilinger entanglement. Nature 403, 515–519 (2000). , , , &
- Simple test for hidden variables in spin-1 systems. Phys. Rev. Lett. 101, 020403 (2008). , , &
- Experimental non-classicality of an indivisible quantum system. Nature 474, 490–493 (2011). et al.
- Security of quantum key distribution using d-level systems. Phys. Rev. Lett. 88, 127902 (2002). , , &
- High-dimensional quantum cryptography with twisted light. New J. Phys. 17, 033033 (2015). et al.
- Quantum imaging technologies. Riv. Nuovo Cimento 37, 273–332 (2014). &
- Twisted photons. Nature Phys. 3, 305–310 (2007). , &
- Experimental high-dimensional two-photon entanglement and violations of generalized Bell inequalities. Nature Phys. 7, 677–680 (2011). , , , &
- Generation and confirmation of a (100 × 100)-dimensional entangled quantum system. Proc. Natl Acad. Sci. USA 111, 6243–6247 (2014). et al.
- Quantum teleportation of multiple degrees of freedom of a single photon. Nature 518, 516–519 (2015). et al.
- Schmidt number for density matrices. Phys. Rev. A 61, 040301 (2000). &
- Entropy vector formalism and the structure of multidimensional entanglement in multipartite systems. Phys. Rev. A 88, 042328 (2013). , &
- Inequalities for the ranks of multipartite quantum states. Linear Algebra Appl. 452, 153–171 (2014). , , &
- Measuring the orbital angular momentum of a single photon. Phys. Rev. Lett. 88, 257901 (2002). , , &
- Measurement of subpicosecond time intervals between two photons by interference. Phys. Rev. Lett. 59, 2044–2046 (1987). , &
- Interference of Photons from Independent Sources PhD thesis, Univ. Vienna (2009).
- Interface between path and orbital angular momentum entanglement for high-dimensional photonic quantum information. Nature Commun. 5, 4502 (2014). et al.
- Quantum secret sharing. Phys. Rev. A 59, 1829–1834 (1999). , &
- Efficient separation of the orbital angular momentum eigenstates of light. Nature Commun. 4, 2781 (2013). , , &
- Automated search for new quantum experiments. Phys. Rev. Lett. Preprint at http://arxiv.org/abs/1509.02749 (2015) , , , &
- Spin-orbit mode selection with a modified Sagnac interferometer. J. Opt. Soc. Am. B 30, 1623–1626 (2013). , &
- Crossed-crystal scheme for femtosecond-pulsed entangled photon generation in periodically poled potassium titanyl phosphate. Phys. Rev. A 89, 042324 (2014). et al.
- Robust interferometer for the routing of light beams carrying orbital angular momentum. New J. Phys. 13, 093014 (2011). et al.
- Entanglement of the orbital angular momentum states of photons. Nature 412, 313–316 (2001). , , &
- Limitations to the determination of a Laguerre–Gauss spectrum via projective, phase-flattening measurement. J. Opt. Soc. Am. B 31, A20–A23 (2014). et al.
- Reconstructing high-dimensional two-photon entangled states via compressive sensing. Sci. Rep. 4, 6542 (2014). , , , &
- Observation of one-way Einstein–Podolsky-Rosen steering. Nature Photon. 6, 596–599 (2012). et al.
- Supplementary information (461 KB)