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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Single-shot integrated multi-photon split state tomography

Jihua Zhang, Andrey A. Sukhorukov

Published Jun 21, 2021• 0 citations
Publisher

Abstract

We propose a segmented coupled waveguide array as a new form of compact optical quantum circuit and apply it for the on-chip multi-photon split state tomography with optimized performance and no need of reconfigurability.
DOI
10.1109/cleo/europe-eqec52157.2021.9542587

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Multi-photon split states, where each photon is in a different input mode, represent an essential resource for various quantum applications. Accordingly, characterisation of such states is important from the fundamental and practical perspectives. We propose a segmented coupled waveguide array as a new form of compact low-loss quantum circuit and apply it for the scalable multi-photon split state tomography with optimized performance and no need of reconfigurability. We develop an optimization algorithm to design the array with minimally necessary number of waveguides and smallest sensitivity to noise in the tomography. Such a novel platform can enable fast, scalable, and fully integrated quantum systems.
Summary form only given. Full characterization of quantum states is increasingly important as ever more complex quantum systems are realized. Quantum state tomography of these systems is a difficult task because individual measurements only give partial information about the underlying density matrix of the system. Thus, conventionally the measurement apparatus must be reconfigured to take multiple measurements in order to fully determine the density matrix. It is accepted that for an W-qubit system an exponentially increasing number of measurements are needed [1]. As a consequence, the complexity of typical quantum state tomography grows exponentially with increasing photon number, which makes characterizing large quantum systems highly challenging. We formulate a concept of on-chip quantum tomography where the complexity scales linearly with the number of photons. This is achieved by using a single specially designed non-reconfigurable linear optical circuit as in Fig. 1(a). Crucially, the number of waveguides in this circuit scales linearly with the number of photons in the state to be measured. Furthermore, our approach is simple and robust, and we demonstrate it experimentally with a specially designed photonic chip.
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Scaling-up optical quantum technologies requires to combine highly efficient multi-photon sources and integrated waveguide components. Here, we interface these scalable platforms: a quantum dot based multi-photon source and a reconfigurable photonic chip on glass are combined to demonstrate high-rate three-photon interference. The temporal train of single-photons obtained from a quantum emitter is actively demultiplexed to generate a 3.8 kHz three-photon source, which is then sent to the input of a tuneable tritter circuit, demonstrating the on-chip quantum interference of three indistinguishable single-photons. Pseudo number-resolving photon detection characterising the output distribution shows that this first combination of scalable sources and reconfigurable photonic circuits compares favourably in performance with respect to previous implementations. A detailed loss-budget shows that merging solid-state based multi-photon sources and reconfigurable photonic chips could allow ten-photon experiments on chip at ∼40{\sim}40∼40 Hz rate in a foreseeable future.