Fully on-chip photonic turnkey quantum source for entangled qubit/qudit state generation

Hatam Mahmudlu, Robert Johanning, Anahita Khodadad Kashi, Albert van Rees, Jörn P. Epping, Raktim Haldar*, Klaus-J. Boller, Michael Kues*

*Corresponding author for this work

Research output: Working paper

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Integrated photonics has recently become a leading platform for the realization and processing of optical entangled quantum states in compact, robust and scalable chip formats with applications in long-distance quantum-secured communication, quantum-accelerated information processing and non-classical metrology. However, the quantum light sources developed so far have relied on external bulky excitation lasers making them impractical, not reproducible prototype devices, hindering scalability and the transfer out of the lab into real-world applications. Here we demonstrate a fully integrated quantum light source, which overcomes these challenges through the combined integration of a laser cavity, a highly efficient tunable noise suppression filter (>55 dB) exploiting the Vernier effect and a nonlinear microring for entangled photon pair generation through spontaneous four-wave mixing. The hybrid quantum source employs an electrically-pumped InP gain section and a Si3N4 low-loss microring filter system, and demonstrates high performance parameters, i.e., a pair emission over four resonant modes in the telecom band (bandwidth ∼1 THz), and a remarkable pair detection rate of ∼620 Hz at a high coincidence-to-accidental ratio of ∼80. The source directly creates high-dimensional frequency-bin entangled quantum states (qubits/qudits), verified by quantum interference measurements with visibilities up to 96% (violating Bell-inequality) and by density matrix reconstruction through state tomography showing fidelities of up to 99%. Our approach, leveraging a hybrid photonic platform, enables commercial-viable, low-cost, compact, light-weight, and field-deployable entangled quantum sources, quintessential for practical, out-of-lab applications, e.g., in quantum processors and quantum satellite communications systems.
Original languageEnglish
Publication statusPublished - 17 Jun 2022


  • Integrated quantum photonics
  • laser-integrated quantum source
  • spontaneous on-chip four-wave mixing
  • Vernier effect noise suppression
  • high-dimensional frequency-bin entangled photon states


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