Operational characterization of multiphoton entanglement in linear optics networks
Project/Area Number 
19F19817

Research Category 
GrantinAid for JSPS Fellows

Allocation Type  Singleyear Grants 
Section  外国 
Review Section 
Basic Section 13010:Mathematical physics and fundamental theory of condensed matter physicsrelated

Research Institution  The University of Tokyo 
Host Researcher 
村尾 美緒 東京大学, 大学院理学系研究科(理学部), 教授 (30322671)

Foreign Research Fellow 
WU JUNYI 東京大学, 理学(系)研究科(研究院), 外国人特別研究員

Project Period (FY) 
20191108 – 20220331

Project Status 
Granted (Fiscal Year 2020)

Budget Amount *help 
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2020: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2019: ¥300,000 (Direct Cost: ¥300,000)

Keywords  Linear optics network / Multiphoton states / Bipartite entanglement / Complementary property / Pauli measurements 
Outline of Research at the Start 
In this research, we aim to establish a theoretical framework of operational characterization of entanglement between modes in composite multiphoton linear optics network systems, such that the gap between the mathematical properties of entanglement in qudit systems and the physical properties of entanglement in multiphoton linear optics networks can be bridged. We will further enhance the accessibility of multiphoton entanglement in linear optics networks by establishing a theoretical framework for superoperational networks of linear optics circuits to share quantum operational power.

Outline of Annual Research Achievements 
n 2019, we have started research on the properties of multiphoton states in linear optics networks (LONs). To tackle the problem of complicated multiphoton statistics in LONs, we have set up a Mathematica computer program for studying multiphoton statistics in LONs for future research. We have characterized the complementary structure of LONs, and shown the quantum coherences of multiphoton states in LONs can be accessed by a set of generalized Pauli measurements, which are mutually complementary with each other. Employing such complementary Pauli measurements, we have derived a theory of quantification of complementary properties, which allows us to physically detect or characterize particular quantum properties of multiphoton states in LONs. As an application of the theory, we have derived a method for detecting entanglement in bipartite multiphoton LONs. This result opens up physical access to quantum properties of multiphoton states in LONs.
Our result has been presented as a poster in the domestic conference 新学術領域「ハイブリッド量子科学」第 10 回領域会議. A paper of the result has been constructed and prepared for publication.

Current Status of Research Progress 
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Following the research plan, in 2019, we have succeeded in setting up a theoretical framework for the analysis of complementary properties of multiphoton states in linear optics networks (LONs). This theoretical framework allows us to access bipartite entanglement in quantum complementary measurements. It is therefore a powerful tool for the theoretical study of entanglement and other relevant properties in LONs, as well as its corresponding experimental realization. As it opens up physical access to quantum coherences of multiphoton states in LONs, we are now ready to go to the next step of our research, which aims to develop a theory of characterization of entanglement with physical operations that are available in experiments. Besides, the characterization of further quantum properties in LONs is now possible, e.g. quantum coherences, state tomography, multipartite entanglement, etc.

Strategy for Future Research Activity 
We will continue our research on the study of multiphoton states in linear optics networks (LONs) in two parallel lines. First, we will try to develop an approach to estimate the fidelity of multiphoton states in LONs in experiments and establish a theory for quantum state tomography in multiphoton LONs in the next step. Based on the theory for quantum state tomography, we will then try to study the quantification of quantum coherences in multiphoton LONs aiming to establish a nogo theory of accessible quantum coherences in multiphoton LONs. Second, we will try to quantify entanglement using our established theoretical framework, and extend it to multipartite entanglement in multiphoton LONs. A nogo theory for accessible entanglement is also expected.

Report
(1 results)
Research Products
(1 results)