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Hybridization of pulse and continuous-wave based optical quantum computation

Tatsuki Sonoyama, Tomoki Sano, Takumi Suzuki, Kazuma Takahashi, Takefumi Nomura, Akito Kawasaki, Asuka Inoue, Takahiro Kashiwazaki, Takeshi Umeki, Masahiro Yabuno, Shigehito Miki, Hirotaka Terai, Kan Takase, Warit Asavanant, Mamoru Endo, Akira Furusawa

Abstract

We propose a pulse and continuous wave (CW) hybrid architecture of continuous-variable measurement-based optical quantum computation utilizing the strengths of both pulsed and CW light. In this architecture, input and ancillary non-Gaussian quantum states necessary for fault-tolerance and universality of quantum computing are generated with pulsed light, whereas quantum processors including continuous-variable cluster states and homodyne measurement systems are operated with CW light. This architecture is expected to enable both generation of quantum states with shorter optical wavepackets and low-loss manipulation and measurement of these states, thus is compatible with ultrafast and low-loss quantum information processing. In this study, as a proof-of-principle, an ultrafast homodyne measurement using CW local oscillator was performed on single-photon states generated with pulsed light. The measured single-photon state's temporal width was around 70 ps and the value of the Wigner function at the origin was W(0,0) = -0.153 +/- 0.003, which is highly non-classical. This will be a core technology for realizing high-speed optical quantum information processing.

Hybridization of pulse and continuous-wave based optical quantum computation

Abstract

We propose a pulse and continuous wave (CW) hybrid architecture of continuous-variable measurement-based optical quantum computation utilizing the strengths of both pulsed and CW light. In this architecture, input and ancillary non-Gaussian quantum states necessary for fault-tolerance and universality of quantum computing are generated with pulsed light, whereas quantum processors including continuous-variable cluster states and homodyne measurement systems are operated with CW light. This architecture is expected to enable both generation of quantum states with shorter optical wavepackets and low-loss manipulation and measurement of these states, thus is compatible with ultrafast and low-loss quantum information processing. In this study, as a proof-of-principle, an ultrafast homodyne measurement using CW local oscillator was performed on single-photon states generated with pulsed light. The measured single-photon state's temporal width was around 70 ps and the value of the Wigner function at the origin was W(0,0) = -0.153 +/- 0.003, which is highly non-classical. This will be a core technology for realizing high-speed optical quantum information processing.

Paper Structure

This paper contains 10 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Results
  3. Methods
  4. Acknowledgement
  5. Author contributions
  6. Competing interests
  7. Data and materials availability

Figures (3)

  • Figure 1: (a) A new optical quantum computing architecture using the pulse-CW hybrid technology experimentally demonstrated in this study. Non-Gaussian states used as initial states or auxiliary states are generated using pulsed light, while the cluster state RIKENfullstack, which serves as the computational platform for measurement-based quantum computing, and the homodyne measurement system are operated using CW light. (b) Pros and cons of the pulsed light and CW light for quantum state generation using heralding scheme and for measurement-based quantum processor.
  • Figure 2: Schematic diagram of the experimental system. IM: Intensity Modulator, WS: Waveshaper, SHG: Second Harmonic Generation, LO: Local Oscillator, WG: Waveguide, OPA: Optical Parametric Amplifier, SNSPD: Superconducting Nanostrip Photon Detector
  • Figure 3: (a) The heatmap of homodyne measurement signals. The colorbar of the figure shows the relation between the color and the frequency of the 2D histogram. The section indicated by the white arrow corresponds to the generated single-photon state. The figure below shows the temporal mode function obtained from the homodyne measurement results by principal component analysis and its time shift. The quadratres corresponding to these temporal modes are calculated and plotted as a histogram in the figure on the left. (b,c) Photon number distribution and Wigner function estimated by quantum state tomography from the calculated quadrature data of the generated quantum state.