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arXiv:2304.12956 · Optica Quantum

Single-active-element demultiplexed multi-photon source

L. M. Hansen, Lorenzo Carosini, Lennart Jehle, Francesco Giorgino, R. Houvenaghel, Michal Vyvlečka, J. C. Loredo, Philip John Walther

Published Sep 28, 2023• 8 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1364/opticaq.494643

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•Aug 16, 2016•1 citation
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.
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)
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.
Advances in photonics will lead to breakthroughs in technology with a similar impact to that resulted from the development of electronics. At the quantum level, photons exhibit some unique features, such as non-classical correlations and bosonic bunching. The manipulation of these quanta of light foresee the construction of quantum devices capable of outperforming their classical counterparts in the purposes for which they are built. Despite a significant progress in developing quantum technologies, several unsolved issues certainly remain: Efficient quantification of quantum correlations in a system, and manipulation of multiple photons at once, are two of such hurdles to be overcome. In this thesis, we tackle these two issues and present experimental progress towards their solution. We first explore quantum entanglement between two single-photons and its effect on phases appearing on the system's wavefunction. The observed phases revealed an intimate connection between entanglement––a purely quantum phenomena––and geometric and topological structures of abstract manifolds: A special case of geometric phases was found to increase monotonically with the amount of entanglement in the system, thus serving as an alternative measure of quantum correlations. We then employed a system of three single-photons, and two concatenated entangling gates, as the basis of a quantum simulation protocol: A three-particle quantum simulator, mimicking the entangling evolution of two particles, is used to experimentally demonstrate that the overhead in measuring concurrence––a measure of two-particle entanglement––can be significantly reduced down to measuring only two observables. At this point, increasing the number of photons being handled proved extremely difficult; the low efficiency of photon sources based on parametric downconversion––the gold-standard and only source at-the-time used for multi-photon experiments––imposed a hard limit on countrates and hence the number of photons to be manipulated. We thus then focused on overcoming this obstacle: We studied a solid-state emitter and its performance as a multi-photon source. We employed a quantum dot-cavity system to show that streams of tens of indistinguishable single-photons are produced, whose temporal-to-spatial demultiplexing serves as a novel kind of multi-photon source. A three-photon source was then built and employed in the first demonstration of multi-photon interference from a solid-state source: We implemented a BosonSampling device with a source that is between one and two orders-of-magnitude more efficient than its downconversion counterpart. The main limiting factors for scaling to higher photon numbers were identified to be not intrinsic to the solid-state emitter, but determined by low detector efficiencies and the probabilistic nature of the demultiplexing scheme. Future improvements on these limitations are expected to allow the generation of sources with a higher number of single-photons, a task that has to date remained otherwise impossible.