RQC Seminar

232nd RQC Seminar

• Speaker

  Dr. Korenobu Matsuzaki
  ( Ultrafast Spectroscopy Research Team / RIKEN Center for Advanced Photonics, and Molecular Spectroscopy Laboratory / RIKEN Pioneering Research Institute )

• Date

  16:00-17:00 (4:00 p.m. - 5:00 p.m.), October 2, 2025 Thursday)

• Venue

  Hybrid(ZOOM・ Wako Main Research Building 3F 345-347 Seminar Room / 研究本館3階 345-347 セミナー室 (C01))

• Title

  Spectroscopical Applications of Entangled Photon Pairs: Experimental Realization of Ultrasensitive and Time-Resolved Measurements

• Inquiries

  norilab_rqc_assist[at]ml.riken.jp

Abstract
Optical spectroscopy is widely used as a versatile analysis tool from basic research to industrial applications. To a great extent, spectroscopy owes its success to the advances in light sources, lasers in particular. Recently, quantum light has emerged as a novel light source. A representative example of quantum light is entangled photon pairs, which can be generated by an optical process called spontaneous parametric down conversion (SPDC). In this study, we report how the unique properties of entangled photon pairs can be exploited to realize novel spectroscopic measurements that are not possible with classical light sources such as a laser.

The first property of entangled photon pairs is that every photon in this light source is paired with another photon. When each of those pairs is split into two, we end up with two groups of photons containing exactly the same number of photons. Such a precise control of the photon number is impossible with classical light because of the statistical fluctuation of the number of photons. This unique property of entangled photon pairs enables us to realize ultrasensitive absorption spectroscopy, which exhibits sensitivity beyond the shot-noise limit. Using this method, we demonstrate the ultrasensitive measurements of the concentration of dye molecules in dilute mixture solutions [1]. Furthermore, we also show its extension to the ultrasensitive detection of molecular chirality based on circular dichroism spectroscopy [2].

The second property is the temporal correlation between paired photons. This property can be utilized to realize time-resolved measurements. Since the temporal correlation exists even when entangled photon pairs are generated from a continuous-wave (cw) laser, this means that time-resolved measurement is feasible without using a pulsed laser at all. Based on this principle, we demonstrate the experimental realization of the simplest time-resolved measurement, i.e., fluorescence lifetime measurement, using entangled photon pairs as the light source [3].

[1] K. Matsuzaki and T. Tahara, Nat. Commun. 13, 953 (2022).
[2] K. Matsuzaki and T. Tahara, ACS Photonics 11, 1376 (2024).
[3] K. Matsuzaki, T. Tahara, and K. Ishii, Japanese patent, No. 7636811 (Feb. 18, 2025).