High-index-contrast nanowires offer unique advantages for manipulation of optical pulses in compact photonic circuits [1]: • high field confinement • precise dispersion engineering Controllable Photon-Pair Generation and Quantum Walks in Nonlinear Waveguide Arrays References [1] A. Peruzzo, M. Lobino, J. C. F. Matthews et al., Science 329, 1500 (2010). [2] A. S. Solntsev, A. A. Sukhorukov, D. N. Neshev, Y. S. Kivshar, Phys. Rev. Lett. 108, 023601 (2012). [3] M. Gräfe, A. S. Solntsev, R. Keil, A. A. Sukhorukov, M. Heinrich, A. Tünnermann, S. Nolte, A. Szameit, Yu. S. Kivshar, Scientific Reports 2, 562 (2012). A. S. Solntsev 1,+, F. Setzpfandt 2 , A. S. Clark 3 , C. W. Wu 1 , M. J. Collins 3 , C. Xiong 3 , F. Eilenberger 2 , A. Schreiber 4 , F. Katzschmann 4 , R. Schiek 5 , W. Sohler 4 , A. Mitchell 6 , C. Silberhorn 4 , B. J. Eggleton 3 , T. Pertsch 2 , A. A. Sukhorukov 1 , D. N. Neshev 1 , and Yu. S. Kivshar 1 1 Nonlinear Physics Centre and Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS), Australian National University, Australia; 2 Institute of Applied Physics, Friedrich-Schiller-University Jena, Germany; 3 CUDOS, University of Sydney, Australia; 4 Universitat Paderborn, Germany; 5 University of Applied Sciences Regensburg, Germany; 6 CUDOS, RMIT University, Australia + Phone: +61-2-6125-3423 Email: sun124@physics.anu.edu.au We demonstrate experimentally simultaneous photon-pair generation and quantum walks in a lithium niobate waveguide array, where the output photon correlations can be controlled by varying the temperature- and wavelength-dependent phase-matching, switching from classical to quantum statistics. Summary • Our work opens a path for implementing combined photon- pair generation and quantum walks in a single device • for the spatial engineering of quantum states in novel active quantum integrated circuits. Introduction Spontaneous Parametric Down-Conversion (SPDC) – enabling generation of photon pairs for quantum optics We combine SPDC with quantum walks in waveguide arrays (WAs) [1] enabling simultaneous photon-pair generation and shaping of quantum correlations [2,3] Dispersion and therefore phase-matching (PM) in WAs is fundamentally different from that in bulk β – propagation constant C - coupling coefficient k ┴ – transverse wavenumber signal idler Experiment pump beam 12nm FWHM filter at 2λ p Ti:LiNbO 3 waveguide array beam splitter lens lens iris iris detector coincidence scheme detector lens SPDC Periodically- poled Birefringent @360-370 ◦ C @240 ◦ C 5mW CW @774-776nm 50mW CW @671nm Periodic poling helps to archive ee-e SPDC phase-matching using largest component of nonlinear-optical tensor d 33 LiNbO 3 birefringecy allows to phase-match oo-e SPDC at a higher temperature with lower photo-refraction both signal and idler are collected from the pumped waveguide 0 signal and idler are collected from the pumped waveguide 0 and/or the neighbouring waveguides 1 and -1 • World first experiment on nonlinear quantum walks • Demonstrates simultaneous bunching and antibunching • Excellent agreement between our theory and experiment Sample with birefringent phase-matching Results Tunability by temperature High coincidence-to-accidental ratio (CAR) classical correlations non-classical correlations • Simple tunability • From classical to quantum statistics Pump wavelength Pump wavelength Experimental Correlations Theoretical Correlations Periodically poled sample Tunability by pump wavelength Control of quantum statistics λ p = λ p = λ p = λ p = λ p = λ p = Theory pump k-space spectrum phase mismatch L propagation constant transverse momentum Photon-pair wave-function in WAs with quadratic nonlinearity Outlook Correlations control by pump beam reshaping pump in two neighbouring next-neighbouring waveguides Friedrich Schiller University of Jena