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arXiv:1205.4341 · New Journal of Physics

Reconfigurable controlled two-qubit operation on a quantum photonic chip

H W Li, S Przeslak, A O Niskanen, J C F Matthews, Alberto Politi, P Shadbolt, Anthony Laing, Mirko Lobino, Mark G. Thompson, Jeremy L. O’Brien

Published Nov 23, 2011• 26 citations
arXivHTMLPDF

Abstract

Integrated quantum photonics is an appealing platform for quantum information processing, quantum communication and quantum metrology. In all these applications it is necessary not only to be able to create and detect Fock states of light but also to programme the photonic circuits that implement some desired logical operation. Here we demonstrate a reconfigurable controlled two-qubit operation on a chip using a multiwaveguide interferometer with a tunable phase shifter. We found excellent agreement between theory and experiment, with a 0.98 ± 0.02 average similarity between measured and ideal operations.

DOI
10.1088/1367-2630/13/11/115009

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Integrated quantum photonics is an appealing platform for quantum information processing, quantum communication and quantum metrology. In all these applications it is necessary not only to be able to create and detect Fock states of light but also to programme the photonic circuits that implement some desired logical operation. Here we demonstrate a reconfigurable controlled two-qubit operation on a chip using a multiwaveguide interferometer with a tunable phase shifter. We found excellent agreement between theory and experiment, with a 0.98 ± 0.02 average similarity between measured and ideal operations.
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Quantum information science aims to harness uniquely quantum mechanical properties to enhance measurement and information technologies, and to explore fundamental aspects of quantum physics. Of the various approaches to quantum computing [1], photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level [2]. Encoding quantum information in photons is also an appealing approach to quantum communication, metrology (eg. [3]), measurement (eg. [4]) and other quantum technologies [5]. However, the implementation of optical quantum circuits with bulk optics has reached practical limits. We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturisation and scalability [6]. Here we report high-fidelity silica-on-silicon integrated optical realisations of key quantum photonic circuits, including two-photon quantum interference and a controlled-NOT logic gate [7]. We have demonstrated controlled manipulation of up to four photons on-chip, including high-fidelity single qubit operations, using a lithographically patterned resistive phase shifter [8]. We have used this architecture to implement a small-scale compiled version of Shorʼs quantum factoring algorithm [9] and demonstrated heralded generation of tuneable four photon entangled states from a six photon input [10]. We have combined waveguide photonic circuits with superconducting single photon detectors [11]. We describe complex quantum interference behaviour in multi-mode interference devices with up to eight inputs and outputs [12], and quantum walks of correlated particles in arrays of coupled waveguides [13]. Finally, we give an overview of our recent work on fundamental aspects of quantum measurement [14,15] and single photon sources [16,17].
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 P π = 44.4 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 97.4 ± 1.0 % . 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.
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Photonic quantum technologies require the integration of high-quality quantum light sources with programmable photonic circuitry to enable on-chip quantum information processing. Semiconductor quantum dots have emerged as a leading platform for quantum light generation, yet their monolithic integration with cryogenic-compatible, programmable photonic circuitry remains challenging. Here we demonstrate a programmable quantum photonic platform that enables simultaneous control of highly coherent quantum dot-based single photon emitters and reconfigurable optical elements at cryogenic temperatures. System-level integration enables individual electrical and optical addressing of active components on a single chip, allowing their concurrent operation while preserving coherent non-classical light emission. We demonstrate multiple quantum-photonic functionalities, including pure single-photon generation, two-photon interference, and resonant transmission and reflection measurements of integrated emitters. These results mark a step from isolated quantum-optical devices towards programmable quantum-photonic hardware platforms capable of combining coherent quantum emitters with large-scale photonic functionality.