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Integrated Photonic Quantum Technologies

Jianwei Wang, Fabio Sciarrino, Anthony Laing, Mark G. Thompson

arXiv:2005.01948v1quant-ph

TL;DR

Understanding how integrated quantum photonics has advanced matters because it is considered a compelling platform for future quantum technologies. This Review surveys its technology and applications, reporting rapid progress over the last decade.

  • Problem

    The central question is how integrated quantum photonics technology and applications have advanced over the last decade.

    Source: Introduction · p. 2

  • Method

    The article reviews progress in integrated quantum photonics technology and applications.

    Source: Introduction · p. 2

  • Results

    The review reports rapid progress in integrated quantum photonics technology and applications over the last decade.

    Source: Introduction · p. 2

  • Takeaways & Limitations

    The review presents integrated quantum photonics as a compelling platform for future quantum technologies.

    Source: Introduction · p. 1

    Full integration still faces technical challenges, including how to manipulate photons.

    Source: Challenges and outlook · p. 7

Abstract

from arXiv · show

Generations of technologies with fundamentally new information processing capabilities will emerge if microscopic physical systems can be controlled to encode, transmit, and process quantum information, at scale and with high fidelity. In the decade after its 2008 inception, the technology of integrated quantum photonics enabled the generation, processing, and detection of quantum states of light, at a steadily increasing scale and level of complexity. Using both established and advanced fabrication techniques, the field progressed from the demonstrations of fixed circuits comprising few components and operating on two photons, to programmable circuitry approaching 1000 components with integrated generation of multi-photon states. A continuation in this trend over the next decade would usher in a versatile platform for future quantum technologies. This Review summarises the advances in integrated photonic quantum technologies (materials, devices, and functionality), and its demonstrated on-chip applications including secure quantum communications, simulations of quantum physical and chemical systems, Boson sampling, and linear-optic quantum information processing.

Introduction

This review surveys a decade of rapid progress in integrated quantum photonics technology and applications. It presents integrated photonics as a compelling platform for future quantum technologies because its functionalities and scaling can support information processing with hundreds or thousands of photons.

Introduction

  • Information processing with hundreds or thousands of photons will almost certainly require the technological functionalities and scaling that only integrated photonics can provide.The introduction describes integrated quantum photonics as a compelling platform for future quantum technologies.Source: Introduction · pp. 1–2
  • The review covers integrated photonics platforms, single-photon sources, linear-optic circuits, and integrated single-photon detectors.It surveys rapid progress in integrated quantum photonics technology over the last decade.Source: Introduction · p. 2
  • The applications reviewed include chip-scale quantum communications, quantum information processing and computing, Boson sampling, and simulations of physical and chemical systems.Source: Introduction · p. 2
  • The review discusses challenges and opportunities for realizing large-scale, monolithic integrated quantum photonics circuits for quantum applications.Source: Introduction · p. 2

Integrated quantum photonic platforms and key devices

Integrated quantum photonics provides a platform for on-chip generation, processing, and detection of quantum light. Its materials, devices, and control techniques support a range of quantum-information tasks.

Integrated platforms

  • IQP platforms include laser-writing silica, SiO2, Si, Si3N4, LN, GaAs, and InP waveguides [14] [17] [18] [25].A 2008 silica-on-insulator circuit demonstrated quantum interference and a controlled-NOT entangling gate [14]; its high fidelity demonstrated platform stability and controllability.Source: Integrated quantum photonic platforms… · p. 2

Qubit encoding and manipulation

Integrated single-photon sources

  • SiO2-waveguides and 4 SFWM-SPSs in Si-microresonators can produce heralded single photons with 52% (50%) heralding efficiency and 95% (91%) photon indistinguishability from separated SPSs.Source: Integrated quantum photonic platforms… · p. 2
  • Bulk-optics multiplexing achieved a 66.7% probability of collecting single photons into a fiber with ∼90% indistinguishability [49].Creating multiple identical QD sources is difficult; demultiplexing photons from one dot into separate modes lowers the overall rate but has been used in Boson sampling [56].Source: Integrated quantum photonic platforms… · p. 3
  • Quantum-dot sources produced 99.1% (99.7%) single-photon purity, 66% (65%) extraction efficiency, and 98.5% (99.6%) indistinguishability in single (several) QD samples.A 2013 resonant-excitation demonstration showed near-optimal emission from a single QD [52].Source: Integrated quantum photonic platforms… · p. 3

Chip-based quantum communications

Integrated photonics provides chip-based platforms for quantum key distribution, including superposition-based, multiplexed, measurement-device-independent, and entanglement-based approaches. The section also describes integrated quantum random-number generators, including a fully device-independent demonstration.

Superposition-based QKD

  • The first chip-to-chip QKD solution paired an InP transmitter with a SiOxNy receiver and supported BB84, coherent-one-way, and differential-phase-shift protocols.The protocols operated at state rates of 560MHz, 860MHz, and 1.76GHz, respectively.Source: Chip-based quantum communications · p. 3
  • Silicon QKD transmitters demonstrated polarization- and time-bin-encoded BB84, including a Cambridge–Lexington link, with kbps–Mbps secret-key rates and 1.0%–5.4% quantum bit error rates,,.Carrier injection and depletion modulation can prepare states at MHz–GHz rates; the demonstrations used external lasers and weak coherent states.Source: Chip-based quantum communications · pp. 3–4

Multiplexing QKD

  • WDM-QKD doubled key rates to 1.11Mbit/s over 20km of emulated fiber, while two Si chips demonstrated four-dimensional space-division QKD with low quantum bit error.The space-division system used a multicore fiber.Source: Chip-based quantum communications · p. 4

MDI-QKD

  • Integrated MDI-QKD demonstrations observed Hong–Ou–Mandel interference visibilities of 46.5±0.8% between InP chips and 46±2% between Si/III-V integrated lasers.The stated maximum achievable visibility is 50%.Source: Chip-based quantum communications · p. 4

Entanglement-based QKD

  • Chip-based entangled time-bin states were distributed over 20km of fiber, and programmable Si chips demonstrated chip-to-chip entanglement distribution and quantum teleportation.Time-bin entangled states were generated in GaAs and Si3N4 systems, including a Si3N4 microresonator spanning visible-to-telecom wavelengths.Source: Chip-based quantum communications · p. 4

Integrated QRNG

  • Integrated QRNGs reached the Gbps regime, including InP devices using random phases from two-laser interference; a Si-chip Bell-inequality violation certified randomness in a fully device-independent scenario [44].Integrated QRNG approaches also used vacuum fluctuation.Source: Chip-based quantum communications · p. 4

On-chip quantum information processing with photons

Photonic quantum information processing uses probabilistic optical gates, while measurement-based quantum computing (MBQC) offers a more resource-efficient approach suited to photons [9–12]. Integrated chips have demonstrated programmable and universal processing alongside entanglement resources for quantum algorithms and simulations.

Gate-based quantum information processing

Programmable quantum chips for multifunctional information processing

  • The first fully programmable two-qubit quantum photonic processor was demonstrated in a silica chip in 2011 [17], combining single-qubit preparation and measurement with two-qubit entangling operation.It performed 1000s of experiments while remaining high fidelity, including a quantum delayed-choice study and an algorithm computing the ground-state energy of molecules.Source: On-chip quantum information processing… · p. 5
  • A Si-photonic processor implemented 98 logic gates with ∼93% average quantum process fidelity and ran multiple algorithms, including a three-example constraint-satisfaction problem.The processor initialized, operated on, and analyzed arbitrary two-qubit states and processes; its gates included CNOT, CZ, CH, and SWAP.Source: On-chip quantum information processing… · p. 5
  • A six-mode SiO2 universal linear-optic circuit demonstrated heralded CNOT, verified Boson sampling, 6-dimensional complex Hadamard operations, and molecular vibrational-dynamics simulation.An eight-mode universal linear-optic circuit was later demonstrated in Si3N4.Source: On-chip quantum information processing… · p. 5

Entanglement GMM and MBQC

  • Integrated sources and circuits enabled entanglement generation, manipulation, and measurement across dual-path, 15-dimensional multi-path, and frequency-bin encodings [43] [44].Demonstrations included a Si chip with ring-resonator SFWM sources, a large-scale Si chip with 16 SFWM sources, and frequency-domain qudit operations using standard fiber components.Source: On-chip quantum information processing… · p. 5
  • On-chip four-qubit cluster states supported photonic MBQC, including Grover’s search for a four-element database; a qutrit-MBQC proof of concept showed high noise robustness.The cluster states included linear and box forms, and three-level four-qubit cluster states were generated in a hydex microresonator.Source: On-chip quantum information processing… · p. 5
  • A Si chip demonstrated four-photon, four-qubit graph-state generation, while a device with near-optimal microresonator FWM sources and reconfigurable circuits certified genuine multipartite entanglement.The graph-state device used four SFWM single-photon sources and a reconfigurable two-qubit linear-optic operator to generate line-graph or star-graph states.Source: On-chip quantum information processing… · p. 5

On-chip sampling of photons and quantum simulation

Integrated photonic circuits have demonstrated multiphoton interference and boson-sampling approaches, and have been used to simulate quantum walks and molecular properties. The section also describes limits on certifying boson-sampling outputs and photon-number thresholds for quantum advantage.

Multiphoton interference

  • Integrated photonics realized three-photon bosonic coalescence in a tritter using laser writing and a device with three coupled interferometers.A tritter extends the beamsplitter from two input modes to three.Source: On-chip sampling of photons and… · p. 6

Boson sampling

  • Boson sampling sends n bosons through an m-mode interferometer; indistinguishable-boson output distributions are classically hard to approximate because event probabilities require matrix permanents.The task is to sample output events from the interferometer’s boson distribution.Source: On-chip sampling of photons and… · p. 6
  • Integrated chips have implemented scattershot Boson sampling and Gaussian Boson sampling together on one silicon-photonic chip.Scattershot sampling was first demonstrated on chip using bulk-optic SPDC sources [15], and later with fully integrated SFWM sources.Source: On-chip sampling of photons and… · p. 6

Validation of Boson sampling

  • Full certification of Boson sampling is believed not possible; demonstrated validation protocols instead aim to rule out the most plausible alternative scenarios, with several experimentally demonstrated using integrated photonics.Source: On-chip sampling of photons and… · p. 6

Regime of quantum advantage

  • More than 20 photons are needed to begin challenging conventional computers, and more than 50 to surpass supercomputers in Boson sampling [quantum-advantage thresholds].The section identifies these as the regimes of quantum advantage and quantum supremacy, respectively.Source: On-chip sampling of photons and… · p. 6

Simulation via quantum walks

  • Discrete-time quantum walks demonstrated single- and two-particle Anderson localization and spin-chain-quench entanglement growth.Continuous-time walks were used to study bosonic coalescence, Fano resonance, coherence and noise in transport, and fast hitting; laser-written 3D chips enabled 2D-walk simulations.Source: On-chip sampling of photons and… · pp. 6–7

Challenges and outlook

The outlook centers on scaling integrated quantum photonics through wafer-scale fabrication, larger photon-number states, and more complete chip integration. The authors anticipate that these advances will support quantum communication, information processing, and simulation.

Challenges and outlook

  • Processing beyond the demonstrated 8-photon states will likely require multiplexed parametric or demultiplexed quantum-dot sources and fast, low-loss switches, with thin-film lithium-niobate switches showing promise.These systems may also enable fast photon manipulation for quantum information processing and communications.Source: Challenges and outlook · p. 7
  • Fully integrated chips combining sources, circuits, and detectors remain unrealized, with cryogenic photon manipulation among the technical challenges; integrated QKD chips are achievable on InP and Si/III-V platforms.Circuits have been integrated with SNSPDs, and sources with SNSPDs, but these demonstrations do not yet constitute a fully integrated quantum chip.Source: Challenges and outlook · p. 7
  • The authors anticipate continued development of large-scale integrated photonic devices and systems to advance quantum communication, quantum information processing, and quantum simulation.They frame wafer-scale fabrication as a route toward these future applications.Source: Challenges and outlook · p. 7
  • Silicon quantum photonic circuits have reached 671 integrated components, and the authors anticipate future circuits with millions of components through wafer-scale, CMOS-compatible fabrication.The 671-component device generated, manipulated, and measured multidimensional entanglement; the projected millions of components are an outlook, not a demonstrated result.Source: Challenges and outlook · p. 7, Figure 6 · p. 13

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