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arXiv:1611.02294 · Laser & Photonics Review

Active demultiplexing of single photons from a solid‐state source

Francesco Lenzini, Ben Haylock, J. C. Loredo, Raphael A. Abrahão, Nor A. Zakaria, Sachin Kasture, Isabelle Sagnes, Aristide Lemaître, Hoang‐Phuong Phan, Dzung Viet Dao, P. Senellart, Marcelo Pereira de Almeida, Andrew G. White, Mirko Lobino

Published Apr 11, 2017• 71 citations
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Abstract

Abstract A scheme for active temporal‐to‐spatial demultiplexing of single photons generated by a solid‐state source is introduced. The scheme scales quasi‐polynomially with photon number, providing a viable technological path for routingnphotons in the one temporal stream from a single emitter tondifferent spatial modes. Active demultiplexing is demonstrated using a state‐of‐the‐art photon source—a quantum‐dot deterministically coupled to a micropillar cavity—and a custom‐built demultiplexer—a network of electro‐optically reconfigurable waveguides monolithically integrated in a lithium niobate chip. The measured demultiplexer performance can enable a six‐photon rate three orders of magnitude higher than the equivalent heralded SPDC source, providing a platform for intermediate quantum computation protocols. image

DOI
10.1002/lpor.201600297

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Abstract A scheme for active temporal‐to‐spatial demultiplexing of single photons generated by a solid‐state source is introduced. The scheme scales quasi‐polynomially with photon number, providing a viable technological path for routingnphotons in the one temporal stream from a single emitter tondifferent spatial modes. Active demultiplexing is demonstrated using a state‐of‐the‐art photon source—a quantum‐dot deterministically coupled to a micropillar cavity—and a custom‐built demultiplexer—a network of electro‐optically reconfigurable waveguides monolithically integrated in a lithium niobate chip. The measured demultiplexer performance can enable a six‐photon rate three orders of magnitude higher than the equivalent heralded SPDC source, providing a platform for intermediate quantum computation protocols. image
Single photons from a solid state source are deterministically routed into different output modes by a fully integrated active optical switch network. Using a state-of-the-art single photon source made of a single quantum dot in a micropillar cavity and an innovative integrated optical demultiplexer, this scheme is capable of creating manifold single photon states. Such states are a crucial resource for photonic quantum information applications including linear optics quantum computation and quantum communications. (Picture: Mirko Lobino, Ph.D. et al., article number 1600297, in this issue)
Temporal-to-spatial mode demultiplexing routes non-simultaneous events of the same spatial mode to distinct output trajectories. This technique has now been widely adopted, because it gives access to higher-number multi-photon states when exploiting solid-state quantum emitters. However, implementations so far have required an always-increasing number of active elements and are therefore rapidly facing resource constraints. Here, we propose and demonstrate a demultiplexing approach that uses only a single active element for routing to, in principle, an arbitrary number of outputs. We employ our device in combination with a high-efficiency single-photon source based on a quantum dot, and measure up to eight demultiplexed highly indistinguishable single photons. We discuss the practical limitations of our approach, and describe in which conditions it can be used to demultiplex, e.g., tens of outputs. Our scheme thus provides a path for the preparation of resource-efficient larger-scale multi-photon sources.
Temporal-to-spatial mode demultiplexing routes non-simultaneous events of the same spatial mode to distinct output trajectories. This technique has now been widely adopted, because it gives access to higher-number multi-photon states when exploiting solid-state quantum emitters. However, implementations so far have required an always-increasing number of active elements and are therefore rapidly facing resource constraints. Here, we propose and demonstrate a demultiplexing approach that uses only a single active element for routing to, in principle, an arbitrary number of outputs. We employ our device in combination with a high-efficiency single-photon source based on a quantum dot, and measure up to eight demultiplexed highly indistinguishable single photons. We discuss the practical limitations of our approach, and describe in which conditions it can be used to demultiplex, e.g., tens of outputs. Our scheme thus provides a path for the preparation of resource-efficient larger-scale multi-photon sources.
We report on a multi-photon source based on active demultiplexing of single photons emitted from a resonantly excited GaAs quantum dot. Active temporal-to-spatial mode demultiplexing is implemented via resonantly enhanced free-space electro-optic modulators, making it possible to route individual photons at high switching rates of 38 MHz. We demonstrate routing into four spatial modes with a high end-to-end efficiency of ≈ 79% and measure a four-photon coincidence rate of 0.17 Hz mostly limited by the single-photon source brightness and not by the efficiency of the demultiplexer itself. We use the demultiplexer to characterize the pairwise indistinguishability of consecutively emitted photons from the quantum dot with variable delay time.
High-purity multi-photon states are essential for photonic quantum computing. Among existing platforms, semiconductor quantum dots offer a promising route to scalable and deterministic multi-photon state generation. However, to fully realize their potential, we require a suitable optical excitation method. Current approaches to multi-photon generation rely on active polarization-switching elements (e.g., electro-optic modulators, EOMs) to spatio-temporally demultiplex single photons. Yet, the achievable multi-photon rate is fundamentally limited by the switching speed of the EOM. Here, we introduce a fully passive demultiplexing technique that leverages a stimulated two-photon excitation process to achieve switching rates only limited by the quantum dot lifetime. We demonstrate this method by generating two-photon states from a single quantum dot without requiring active switching elements. Our approach significantly reduces the cost of demultiplexing while shifting it to the excitation stage, enabling loss-free demultiplexing and effectively doubling the achievable multi-photon generation rate when combined with existing active demultiplexing techniques.
The non-deterministic nature of photon sources is a key limitation for single-photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single-photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon-based correlated photon pair sources in the telecommunications band, demonstrating a 62.4% increase in the heralded single-photon output without an increase in unwanted multipair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two-photon interference, required at the core of optical quantum computing and quantum communication protocols. Photonic quantum technologies will require efficient single-photon sources and spatial multiplexing has been explored as a route to achieve this. Here, the authors present a scheme to integrate several single-photon sources using spatial multiplexing for on-chip applications at telecommunications wavelengths.