On-chip transverse-mode entangled photon pair source
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Abstract
Integrated entangled photon pair source is an essential resource for both fundamental investigations and practical applications of quantum information science. Currently there have been several types of entanglement, among which the transverse-mode entanglement is becoming attractive because of its unique advantages. Here, we report an on-chip transverse-mode entangled photon pair source via the spontaneous four-wave mixing processes in a multimode silicon waveguide. Transverse-mode photon pairs are verified over multiple frequency channels within a bandwidth of ~2 THz, and a maximally entangled Bell state is also produced with a net fidelity of 0.96 ± 0.01. Our entangled photon pair source is the key element for quantum photonics based on transverse-mode, and also has the possibility to extend to higher-dimensional Hilbert space. Furthermore, the transverse-mode entanglement can be converted coherently to path and polarization entanglement, which paves the way to realizing highly complex quantum photonic circuits with multiple degrees of freedom.Entangled photon sources: compact and capableOn-chip transverse-mode entangled photons pave the way towards high-dimensional quantum state generation with multiple degrees of freedom. On-chip integration is desired for its compactness, stability and scalability, while the use of transverse modes in multimode waveguides can prove beneficial in wavelength modulation, dispersion and polarization. Now, Dao-Xin Dai, Xi-Feng Ren and colleagues from University of Science and Technology of China and Zhejiang University, China combine these two features to produce an on-chip transverse-mode entangled photon pair source attractive towards the realization of highly complex quantum photonic circuits. Their device exploits spontaneous four-wave mixing, a nonlinear optical process involving intermodulation, in a 3-mm-long multimode silicon waveguide. They verified the transverse-mode photon pairs over multiple frequency channels within a bandwidth of ∼2 THz, achieving a maximally entangled Bell state with a net fidelity of 0.96 ± 0.01.