A silicon source of heralded single photons at 2 μm

Abstract

Mid-infrared integrated quantum photonics is a promising platform for applications in sensing and metrology. However, there are only a few examples of on-chip single-photon sources at these wavelengths. These have limited performances with respect to their C-band counterparts. In this work, we demonstrate a new approach to generate heralded single photons in the mid-infrared on a silicon chip. By using a standard C-band pump, the inter-modal spontaneous four-wave mixing enables the generation of the herald idler at 1259.7 nm and the heralded signal at 2015 nm. The idler photon is easily detected with a common infrared single-photon detector while the signal photon is upconverted to visible before its detection. In this way, we are able to operate a mid-infrared source without the need for mid-infrared detectors and laser sources. By measuring a heralded g (2) of 0.23 ± 0.08, we demonstrate the single-photon behavior of the source as well as the feasibility of multi-photon coincidence measurements beyond 2 μm with our setup. The source exhibits a high-intrinsic heralding efficiency of (59 ± 5)%, a maximum coincidence to accidental ratio of 40.4 ± 0.9, and a generation probability of (0.70 ± 0.10) W −2 .

2 µm Ghost Spectroscopy with an Integrated Silicon Quantum Photonics Source

“…[28] We measured a fourfold improvement of the CAR with respect to the state of the art of silicon sources, compared at the same net coincidence rate of ≈ 1 Hz. [19,20] The maximum CAR achieved (105.8 ± 2.5) is more than two times higher with respect to the state of the art in integrated photonics [19] and close to the values reported for 𝜒 (2) crystals. [21] To complete the characterization of the source, we also measured the heralded second-order coherence function, g…”

“…The low propagation losses 1.8 dBcm -1 at 1550 nm allows CW pumping of SFWM unlikely in our previous work. [19] The use of an intermodal process has three main advantages: far detuning from the pump and high non-degeneracy of idler and signal, filter-free narrowband generation, and high tunability of the signal wavelength while keeping the idler almost unchanged. [23,24] These peculiarities enable easy pump and Raman noise rejection, IR-MIR entangled pair generation with easy and broadband tunability of the MIR photon.…”

“…Using the signal as the heralded photon and the idler as the herald photon, the single-photon behavior of the source was proved by measuring the heralded g (2) (0) (g (2) H (0)). [19,28] A Hanbury-Brown and Twiss (HBT) interferometer is used in the signal line to carry out this measurement. The value of the g H (0) = 0.06 ± 0.02 at 10.5 mW, we were able to confirm the anti-bunching regime of the generated photon in the MIR and, hence, the single photon regime of our source.…”

Ultra-efficient generation of time-energy entangled photon pairs in a InGaP Photonic Crystal Cavity

“…Different routes have been explored in this regard, for example the emission of defects in diamonds or semiconductors [8][9][10] , artificial solid state quantum emitters such as quantum dots [11][12][13] , and parametric processes exploiting intrinsic material nonlinearity. Correlated photon pairs spontaneously generated via parametric processes can be used to build heralded SPSs [14][15][16][17][18] , in which the detection of one photon in one input channel heralds the presence of its twin photon in the other. Such processes can provide highly coherent entangled states but, relying on spontaneous processes, the pair emission is random and the source is probabilistic, making it crucial to achieve the highest generation efficiency.…”

Ultra-efficient generation of time-energy entangled photon pairs in an InGaP photonic crystal cavity

“…Different routes have been explored in this regard, for example, the emission of defects in diamonds or semiconductors [8][9][10] , artificial solid-state quantum emitters such as quantum dots [11][12][13] , and parametric processes exploiting intrinsic material nonlinearity. Correlated photon pairs spontaneously generated via parametric processes can be used to build heralded SPSs [14][15][16][17][18] , in which the detection of one photon in one input channel heralds the presence of its twin photon in the other. Such processes can provide highly coherent entangled states but, relying on spontaneous processes, the pair emission is random and the source is probabilistic, making it crucial to achieve the highest generation efficiency.…”