On-chip tunable quantum interference in a lithium niobate-on-insulator photonic integrated circuit
Andreas Maeder, Giovanni Finco, Fabian Kaufmann, Alessandra Sabatti, Jost Kellner, Robert J. Chapman, Rachel Grange
Abstract
Abstract Programmable interferometric circuits are at the heart of integrated quantum photonic processors. While the lithium niobate-on-insulator platform has the potential to advance integrated quantum photonics due to its strong nonlinearity and tight mode confinement, the demonstration of reconfigurable two-photon interference has not yet been achieved. Here, we design, fabricate and characterize the building block of such interferometric networks in the form of a 2 × 2 Mach–Zehnder Interferometer. We use a thermo-optic phase shifter to achieve stable performance with a power consumption of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>P</mml:mi> <mml:mi>π</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>44.4</mml:mn> </mml:mrow> </mml:math> mW and sub-microsecond switching times. We demonstrate the effectiveness of our device for quantum applications by measuring single-photon routing with up to 34 dB extinction ratio. We show Hong-Ou-Mandel interference with fully tunable visibilities reaching a maximum value of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>97.4</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.0</mml:mn> <mml:mi mathvariant="normal">%</mml:mi> </mml:mrow> </mml:math> . As part of large scale quantum photonic circuits, this building block will facilitate reconfigurable and tunable photonic processing units integrated alongside non-classical light sources.