Integrated AlGaAs source of highly indistinguishable and energy-time entangled photons

Abstract

The generation of nonclassical states of light in miniature chips is a crucial step toward practical implementations of future quantum technologies. Semiconductor materials are ideal for achieving extremely compact and massively parallel systems and several platforms are currently under development. In this context, spontaneous parametric downconversion in AlGaAs devices combines the advantages of room temperature operation, possibility of electrical injection, and emission in the telecom band. Here we report on a chip-based AlGaAs source, producing indistinguishable and energy-time entangled photons with a brightness of 7.2×106 pairs/s and a signal-to-noise ratio of 141±12. Indistinguishability between the photons is demonstrated via a Hong–Ou–Mandel experiment with a visibility of 89±3%, mainly limited by the reflectivity of the chip facets, while energy-time entanglement is tested via a Franson interferometer leading to a visibility of 96±4

Integrated sources of entangled photons at the telecom wavelength in femtosecond-laser-written circuits

“…Entanglement is a powerful feature of quantum systems and a key resource in quantum information science being widely exploited to perform exclusive quantum protocols as teleportation [1], entanglement swapping [2] and repeaters or to outperform classical performances in metrology [3], criptography [4] and computation [5,6]. In the last decade, the unique properties of entanglement have stimulated the development of efficient and versatile sources of entanglement carriers [7][8][9]. In this framework, photons represent a favourable choice due to weak decoherence, the possibility of implementing entanglement in several degrees of freedom and the availability of efficient and robust optical components for routing and manipulation of the generated photons.…”

Generation and symmetry control of quantum frequency combs

“…The modes involved in the nonlinear process are a TE Bragg mode for the pump beam around 765 nm and TE 00 and TM 00 modes for the photon pairs in the C-telecom band. Note that, for this device, the group velocity mismatch between the two photons of each pair is so small that no off-chip com-pensation is required to preserve their indistinguishability [23,26]. The photon pairs are thus emitted in very good approximation with a joint spectral amplitude centered in ω − = 0 and symmetric in the ω − variable, enabling a direct implementation of our method.…”

Multi-User Quantum Key Distribution with Entangled Photons from a Semiconductor Chip

“…1b. The device is pumped by a Ti:saphir laser at 778 nm and generates photon pairs within a large bandwidth (about 120 nm) around 1556 nm via type-II spontaneous parametric down conversion (SPDC) [4]. The weak birefringence of the TE and TM guided modes at telecom wavelengths allows direct generation of the polarization entangled Bell state:…”