Generation of quantum‐entangled twin photons by waveguide nonlinear‐optic devices

Abstract

This paper reviews the quasi-phase-matched (QPM) waveguide nonlinear-optic device technologies for generation of quantum-entangled twin photons indispensable for quantuminformation techniques. After a brief introduction to the concept of entanglement, quantum theory analysis of twin-photon generation (TPG) is outlined to clarify the properties of twin photons. Then, methods for entangled-photon generation are discussed. Practical design and theoretical performances of LiNbO3 waveguide QPM TPG devices, as well as the fabrication techniques, are described. Finally, experimental demonstrations of polarization-entangled twin-photon generation by waveguide Type-I and Type-II QPM TPG devices are presented.C h a n n e l W a v e g u i d e L i N b O 3 C r y s t a l D o m a i n -I n v e r t e d G r a t i n g f o r T y p e -I I Q P M P u m p W a v e O u t p u t C r o s s -P o l a r i z e d T w i n P h o t o n s w

Generation and Detection of Continuous Variable Quantum Vortex States via Compact Photonic Devices

“…The power of the pump is halved, and these two pumps propagating within waveguides 1 and 2 cross two areas specially engineered in order to maximize the nonlinear effect of the substrate. A large conversion efficiency between the pump and the daughter fields is obtained by tailoring the nonlinearity of the material by periodically poling (PPLN), enabling quasi-phase matching of the propagation constants (QPM) [40]. The period of the grating Λ is tailored such that…”

“…is the single-mode squeezing operator and s = κL p the squeezing parameter generated in a poling area of length L p , which we have chosen to be real in order to simplify [40].…”

Hyperentangled photon sources in semiconductor waveguides

“…Even though different types of nonlinear crystals have been used for generating paired photons via SPDC, driven by the demand for high-efficiency single and two-photon sources, and the need for on-chip integration of quantum computing, there has been a focus on periodically poled lithium niobate (PPLN) and potassium titanyl phosphate (PPKTP) waveguides. This class of sources makes use of quasi phase matching (QPM) to provide access to the highest nonlinear coefficient of the material [8]. In these waveguide sources, the photon pair generation rates are increased by orders of magnitude over their bulk crystal counterparts, and the use of well-confined waveguide modes makes the collection of generated photons in optical circuits easier.…”

“…To date, energy-time and polarization entanglement have been demonstrated using these waveguide sources in various configurations [8]. Hyperentanglement has not been demonstrated so far.…”

Generation of polarization entangled photons using concurrent type-I and type-0 processes in AlGaAs ridge waveguides

“…Periodically poled LN (PPLN) and KTP (PPKTP) waveguides using quasi-phase-matching (QPM) have proven to be the most useful due to the significantly enhanced efficiency they provide. To produce polarization entangled photons from these waveguides, various schemes have been exploited using type-0 and type-I processes in which the pump is TM (V) polarized and the generated photons are copolarized in TM and TE (H) modes, respectively, or type-II process in which the pump is TE polarized whereas the generated photons are cross-polarized in both TE and TM modes [2]. However, all these devices cannot be integrated with pump lasers on the same chip, which is essential for future large-scale quantum information processing.…”