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arXiv:1106.5970 · Physical Review A

Generation of modal- and path-entangled photons using a domain-engineered integrated optical waveguide device

Jasleen Lugani, Sankalpa Ghosh, Krishnan Thyagarajan

Published Jun 24, 2011• 18 citations
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Abstract

Integrated optical devices are expected to play a promising role in the field of quantum information science and technology. In this paper we propose a scheme for the generation of nondegenerate, copolarized, modal, and path-entangled photons using a directional coupler and an asymmetric $\mathsf{Y}$-coupler geometry in type-0 phase-matched domain-engineered lithium niobate (LN) waveguide. The nonlinearity in LN is tailored in such a way that quasi-phase-matching conditions for two different spontaneous parametric down-conversion processes are obeyed simultaneously, leading to a modal and path-entangled state at the output. Assuming typical values of various parameters, we show, through numerical simulations, that an almost maximally entangled state is achievable over a wide range of waveguide parameters. For the degenerate case, the proposed scheme gives a NOON state for $N$ $=$ 2. The generated entangled photon pairs should have potential applications in quantum information schemes and also in quantum metrology. By appropriate domain engineering and component designing, the idea can be further extended to generate hyperentangled and two-photon multipath-entangled states, which may have further applications in quantum computation protocols.

DOI
10.1103/physreva.83.062333

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In this paper, we propose an integrated optic waveguide device employing a modified Mach–Zehnder interferometer, capable of generating nondegenerate, hyperentangled photon pairs. The geometry enables multiple (eight) type-II phase-matched spontaneous parametric downconversion processes simultaneously, resulting in a biphoton state, which is simultaneously entangled in polarization and spatial modes. Using an electro-optic phase modulator, we show the possibility of altering modal entanglement without affecting polarization entanglement. Such switchable, maximally entangled photon pairs, entangled in multiple degrees of freedom, should be very useful in various on-chip quantum optics experiments and in the implementation of quantum information protocols employing higher dimensional entanglement.
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