Engineering spectrally unentangled photon pairs from nonlinear microring resonators by pump manipulation

Abstract

The future of integrated quantum photonics relies heavily on the ability to engineer refined methods for preparing the quantum states needed to implement various quantum protocols. An important example of such states is quantum-correlated photon pairs, which can be efficiently generated using spontaneous nonlinear processes in integrated microring-resonator structures. In this work, we propose a method for generating spectrally unentangled photon pairs from a standard microring resonator. The method utilizes interference between a primary and a delayed secondary pump pulse to effectively increase the pump spectral width inside the cavity. This enables on-chip generation of heralded single photons with state purities in excess of 99% without spectral filtering.

Programmable four-photon graph states on a silicon chip

“…We corroborate V by measuring the unheralded second-order correlation function g (2) (0) for the eight modes of our four on-chip sources, implying 29 heralded purities between 0.82 and 0.92 (the Supplementary Information contains a full listing). New parametric source designs will further improve brightness and purity on-chip 19,30,31 .…”

Progress on Integrated Quantum Photonic Sources with Silicon

“…However, the filtering process will cause extra loss. Another solution is the engineering of the joint spectra intensity with microring resonators, such as the recently proposed experimental work and theoretical protocols . A high heralding efficiency is critical for scaling photon numbers due to the exponential increase in losses with number of photons.…”

Unidirectional frequency conversion in microring resonators for on-chip frequency-multiplexed single-photon sources

“…high spectral purity. Another solution is to modify the pump spectrum as shown in [29]. Our design achieves a signal linewidth, s g , that is smaller than the pump, p g , and idler, i g .…”

“…{ }are orthonormal signal and idler Schmidt modes and λ k the Schmidt coefficients. The square of the signal density matrix (originating from a partial trace of the joint state operator over the idler sub-space) is used to define the spectral purity of heralded photons[29] The maximum spectral purity is achieved when the spectral width of the pump pulse is much larger than the width of the pump mode and the approximation A p ≈1 can be made inequation (A38).…”