Efficient backcasting search for optical quantum state synthesis

TL;DR

This paper introduces an efficient backcasting method for designing optical quantum state synthesizers, reducing computational complexity and detector requirements, thereby advancing non-Gaussian state preparation for quantum technologies.

Contribution

The authors propose a novel backcasting approach to optimize OQSS circuit design, simplifying simulation and detector specifications for non-Gaussian state synthesis.

Findings

Photon number per detector is at most 2, reducing detector complexity.

Backcasting approach effectively simplifies the simulation process.

Method enables preparation of a wide variety of non-Gaussian states.

Abstract

Non-Gaussian states are essential for many optical quantum technologies. The so-called optical quantum state synthesizer (OQSS), consisting of Gaussian input states, linear optics, and photon-number resolving detectors, is a promising method for non-Gaussian state preparation. However, an inevitable and crucial problem is the complexity of the numerical simulation of the state preparation on a classical computer. This problem makes it very challenging to generate important non-Gaussian states required for advanced quantum information processing. Thus, an efficient method to design OQSS circuits is highly desirable. To circumvent the problem, we offer a scheme employing a backcasting approach, where the circuit of OQSS is divided into some sublayers, and we simulate the OQSS backwards from final to first layers. Moreover, our results show that the detected photon number by each detector is at most 2, which can significantly reduce the requirements for the photon-number resolving detector. By virtue of the potential for the preparation of a wide variety of non-Gaussian states, the proposed OQSS can be a key ingredient in general optical quantum information processing.