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Quantum circuits with many photons on a programmable nanophotonic chip

Published 3 Mar 2021 in quant-ph | (2103.02109v1)

Abstract: Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms. Present day photonic quantum computers have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware-software system for executing many-photon quantum circuits using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. It enables remote users to execute quantum algorithms requiring up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and genuine photon number-resolving readout on all outputs. Multi-photon detection events with photon numbers and rates exceeding any previous quantum optical demonstration on a programmable device are made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra, and graph similarity.

Citations (421)

Summary

  • The paper demonstrates a full-stack, programmable nanophotonic chip that executes many-photon quantum circuits with detection rates up to 10,000 events/s.
  • The research integrates strong squeezing and a four-mode interferometer to enable remote programming and verify non-classical output.
  • Quantum algorithms including Gaussian boson sampling, molecular vibronic spectra, and graph similarity analysis were successfully implemented, suggesting a scalable path for quantum computing.

Quantum Circuits with Many Photons on a Programmable Nanophotonic Chip

This paper details the development and demonstration of a full-stack system for executing quantum algorithms using a programmable nanophotonic chip, capable of handling many-photon quantum circuits. The integration of this device is situated in the broader context of advancements in quantum computing, where various architectures are being explored to determine their efficacy in executing quantum computations that surpass classical capabilities.

Technical Overview

The nanophotonic chip, operating at room temperature, allows the execution of quantum algorithms using up to eight modes of strongly squeezed vacuum states, initialized as two-mode squeezed states. A programmable four-mode interferometer facilitates a general transformation, and the system is equipped with genuine photon number-resolving detection capabilities at all outputs.

Key Features and Innovations

  1. Many-Photon Quantum Circuits: By leveraging strong squeezing and efficient sampling rates, the platform outperforms previous demonstrations by achieving higher photon numbers and detection rates on a programmable device.
  2. Programmability and Remote Accessibility: The chip enables remote programming by end-users, who can execute quantum circuits without needing deep expertise in the underlying hardware. This is accomplished through interfacing with a fully automated control system.
  3. Non-Classicality and Demonstrated Algorithms: The authors verified the non-classicality of the device output, a crucial prerequisite for tasks that aim to establish quantum supremacy. The device was used to demonstrate three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra, and graph similarity.

Numerical Results and Claims

  • Photon Number Events: The device achieves four-photon detection at 10,000 events/s, ten-photon events at 270 events/s, and nineteen-photon events at 0.3 events/s, which surpasses the detection rates of prior programmable photonic devices.
  • Demonstrations of Quantum Algorithms: The Gaussian boson sampling demonstration achieved the largest number of detected photons to date, with 15-photon events observed. These results exhibit an agreement with theoretical predictions, suggesting robust performance of the architecture against the model.

Implications and Prospects

The practical implementation of a cloud-accessible, programmable nanophotonic chip paves the way for wider experimental verification of the quantum advantage hypothesis. With ongoing improvements in photon source efficiency and reduced system losses, the scalability of such systems could lead to practical and commercially viable quantum computing applications. Furthermore, the demonstration of graph similarity analysis on this platform indicates a promising expansion of photonic devices into complex computational problem domains.

These developments suggest a transformative step in leveraging integrated photonics for quantum computation. As the chip and its integrated components become more sophisticated, their role in advancing the field of quantum computing will likely become pivotal, especially in tasks traditionally resistant to classical computational methods. Future work will include enhancing the scalability of these devices and expanding the range of quantum algorithms that can be implemented. These efforts will aim to move beyond proof-of-principle experiments towards realizing the full potential of quantum photonics in practical applications.

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