npj Quantum Information (May 2024)

High-fidelity four-photon GHZ states on chip

  • Mathias Pont,
  • Giacomo Corrielli,
  • Andreas Fyrillas,
  • Iris Agresti,
  • Gonzalo Carvacho,
  • Nicolas Maring,
  • Pierre-Emmanuel Emeriau,
  • Francesco Ceccarelli,
  • Ricardo Albiero,
  • Paulo Henrique Dias Ferreira,
  • Niccolo Somaschi,
  • Jean Senellart,
  • Isabelle Sagnes,
  • Martina Morassi,
  • Aristide Lemaître,
  • Pascale Senellart,
  • Fabio Sciarrino,
  • Marco Liscidini,
  • Nadia Belabas,
  • Roberto Osellame

DOI
https://doi.org/10.1038/s41534-024-00830-z
Journal volume & issue
Vol. 10, no. 1
pp. 1 – 7

Abstract

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Abstract Mutually entangled multi-photon states are at the heart of all-optical quantum technologies. While impressive progresses have been reported in the generation of such quantum light states using free space apparatus, high-fidelity high-rate on-chip entanglement generation is crucial for future scalability. In this work, we use a bright quantum-dot based single-photon source to demonstrate the high fidelity generation of 4-photon Greenberg-Horne-Zeilinger (GHZ) states with a low-loss reconfigurable glass photonic circuit. We reconstruct the density matrix of the generated states using full quantum-state tomography reaching an experimental fidelity to the target state of $${{{{\mathcal{F}}}}}_{{{{{\rm{GHZ}}}}}_{4}}=(86.0\pm 0.4)\, \%$$ F GHZ 4 = ( 86.0 ± 0.4 ) % , and a purity of $${{{{\mathcal{P}}}}}_{{{{{\rm{GHZ}}}}}_{4}}=(76.3\pm 0.6)\, \%$$ P GHZ 4 = ( 76.3 ± 0.6 ) % . The entanglement of the generated states is certified with a semi device-independent approach through the violation of a Bell-like inequality by more than 39 standard deviations. Finally, we carry out a four-partite quantum secret sharing protocol on-chip where a regulator shares with three interlocutors a sifted key with up to 1978 bits, achieving a qubit-error rate of 10.87%. These results establish that the quantum-dot technology combined with glass photonic circuitry offers a viable path for entanglement generation and distribution.