Nonlinear Squeezing for Measurement-Based Non-Gaussian Operations in Time Domain

Shunya Konno,Radim Filip,Atsushi Sakaguchi,Akira Furusawa,Hisashi Ogawa,Masaya Kobayashi,Jun-Ichi Yoshikawa,Warit Asavanant,Petr Marek

doi:10.1103/physrevapplied.15.024024

Shunya Konno, Radim Filip + Show 7 more

Open Access

https://doi.org/10.1103/physrevapplied.15.024024

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Abstract

Quantum non-Gaussian gate is a missing piece to the realization of continuous-variable universal quantum operations in the optical system. In a measurement-based implementation of the cubic phase gate, a lowest-order non-Gaussian gate, non-Gaussian ancillary states that has a property we call nonlinear squeezing are required. This property, however, has never been experimentally verified. In this paper, we generate a superposition between a vacuum state and a single photon state whose nonlinear squeezing are maximized by the optimization of the superposition coefficients. The nonlinear squeezing is observed via real-time quadrature measurements, meaning that the generated states are compatible with the real-time feedforward and are suitable as the ancillary states for the cubic phase gate in time domain. Moreover, by increasing the number of the photons, it is expected that nonlinear squeezing can be further improved. The idea presented here can be readily extended to the higher-order phase gates [P. Marek et al., Phys. Rev. A 97, 022329 (2018)]. As such, this work presents an important step to extend the CV quantum information processing from Gaussian regime to non-Gaussian regime.

Highlights

Continuous-variable (CV) quantum computation using optical systems is currently one of the most promising approaches to a scalable and practical quantum computation
The nonlinear squeezing is observed via real-time quadrature measurements, meaning that the generated states are compatible with real-time feedforward and are suitable as ancillary states for the cubic phase gate in the time domain
For further detailed discussions regarding the generated states, see Appendixes B and C. These results indicate that by making a non-Gaussian superposition, we can experimentally generate states with nonlinear squeezing (NLSQ) that have an exponentially rising wave packet appropriate for the implementation of the cubic phase gate in the time domain

Summary

Introduction

Continuous-variable (CV) quantum computation using optical systems is currently one of the most promising approaches to a scalable and practical quantum computation. Large-scale Gaussian cluster states, the computational resource states for measurementbased quantum computation [1,2], have been experimentally realized using the time-domain-multiplexing method [3,4,5,6]. By implementing appropriate measurements on the Gaussian cluster states, universal CV quantum operations can be realized. By combining basis-programmable homodyne measurements with timedomain cluster states, Gaussian operations, i.e., linear transformations of the quadrature operators, have been demonstrated [7,8]. These experimental results demonstrate the potentials of the CV optical systems for quantum computation

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