Monolithic semiconductor chips as a source for broadband wavelength-multiplexed polarization entangled photons

Abstract

Generating entangled photons from a monolithic chip is a major milestone towards real-life applications of optical quantum information processing including quantum key distribution and quantum computing. Ultrabroadband entangled photons are of particular interest to various applications such as quantum metrology and multi-party entanglement distribution. In this work, we demonstrate the direct generation of broadband wavelength-multiplexed polarization entangled photons from a semiconductor chip for the first time. Without the use of any off-chip compensation or interferometry, entangled photons with a signal-idler separation as large as 95 nm in the telecom band were observed. The highest concurrence of 0.98±0.01 achieved in this work is also the highest, to the best of our knowledge, comparing to all previously demonstrated semiconductor waveguide sources. This work paves the way for fully integrated, ultrabroadband sources of polarization entangled photons.

Generation and manipulation of entangled photons on silicon chips

“…Lv et al [61] generated polarization entanglement by means of the birefringence of a single SWW. Various polarization entanglement sources based on an χ (2) nonlinear waveguide made of (Al)GaAs have also been demonstrated [62][63][64][65][66]; these experiments employing the direct band-gap materials paved the way to the realization of a polarization entanglement source driven by current injection [67,68]. These results show important steps toward the realization of an integrated quantum information system using the polarizations of light.…”

Optimizing the spectro-temporal properties of photon pairs from Bragg-reflection waveguides

“…Finally, we use the scheme in Figure 9 for generating polarization entangled states with multiple spectral bands that are free from temporal delay compensation [17,18,33]. In the absence of background light, the density matrix of the polarization entangled state takes the form [19], ρ = α |HV HV| + D |VH HV| The comparison of the HOM dips at the degeneracy for (a) the graded and (b) M-core BRW structures without any filters reveals the clear difference in the spectral indistinguishability of signal and idler.…”

Optimal analysis of ultra broadband energy-time entanglement for high bit-rate dense wavelength division multiplexed quantum networks

“…already been demonstrated 10,18 , only a few experiments have considered DWDM QKD with, to date, in up to eight channel pairs 10 . However, in all of these realizations, the optimal analyzer settings showed a strong wavelength dependence, such that entanglement has been measured in multiple channel pairs sequentially 10,19,20 , i.e. the analyzer settings had to be adapted for each individual channel pair.…”