Direct measurement of time-frequency quantum channels of photons for the construction of the quantum internet infrastructure

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04915
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: Osaka University
• Principal Investigator: Ogawa Kazuhisa 大阪大学, 量子情報・量子生命研究センター, 講師 (80772574)
• Co-Investigator(Kenkyū-buntansha): 富田 章久 北海道大学, 情報科学研究院, 教授 (60501434)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 量子測定 / 量子トモグラフィ / 直接測定 / 弱測定 / 光量子通信

Outline of Final Research Achievements

The dynamics of a quantum system are characterized by three components: quantum state, quantum process, and quantum measurement. The proper measurement of these components is a crucial issue in quantum information processing. Recently, direct measurement methods have been proposed and demonstrated wherein each complex matrix element of these three components is obtained separately, without the need for quantum tomography of the entire matrix. In this study, we have proposed a theoretical framework to systematically derive direct measurement methods for these three components. Following this framework and further utilizing the basis-shift unitary transformation, we have derived the most efficient direct measurement method using qubit probes. Additionally, we have experimentally demonstrated the feasibility of the direct measurement method of quantum states using optical pulse trains.

Free Research Field

量子情報工学

Academic Significance and Societal Importance of the Research Achievements

本研究は、量子情報処理の効率を向上させるための新たな理論的枠組みを提案している。つまり、量子状態、量子過程、量子測定の3つの要素を個別に直接測定する方法を体系的に導出し、これによって量子トモグラフィーの使用を回避できる。その結果、計算資源の節約と測定時間の短縮が可能になり、さらに、光パルス列を用いた実験により提案手法の実現可能性も示しており、学術的な進展だけでなく、光量子通信による量子情報処理の実用化に向けた一歩となると考えられる。