Takahashi Group

Quantum Sensing & Quantum Dynamics

Takahashi lab @ USC Phys Chem/QIS/CMP

We are an interdisciplinary experimental research group overlapping in the areas of Physical Chemistry (Phys Chem), Quantum Information Science (QIS) and Condensed Matter Physics (CMP). We all know quantum mechanics (QM) can explain electronic states of atoms and molecules. QIP is fascinating and has the potential to advance our technology, but QM effect is often hidden in noise and is difficult to see directly. Can we control/manipulate quantum phenomena? How can we build a desired quantum system? How quantum technology can be used to uncover molecular and materials properties? Can a QM-assisted measurement outperform a conventional measurement? We are interested to overcome those challenges and to solve scientific puzzles using experiment with unique instrumentation and intuitive theory.

What we've done recently

We introduce a couple of recent research highlights here.

Determination of local defect density in diamond by double electron-electron resonance

S. Li,* H. Zheng,* Z. Peng,* M. Kamiya, T. Niki, V. Stepanov, A. Jarmola, Y. Shimizu, S. Takahashi, A. Wickenbrock and, D. Budker, Phys. Rev. B 104, 094307 (2021). 

Magnetic impurities in diamond influence the relaxation properties and thus limit the sensitivity of magnetic, electric, strain, and temperature sensors based on nitrogen-vacancy color centers. Diamond samples may exhibit significant spatial variations in the impurity concentrations hindering the quantitative analysis of relaxation pathways. Here, we present a local measurement technique which can be used to determine the concentration of various species of defects by utilizing double electron-electron resonance. This method will help to improve the understanding of the physics underlying spin relaxation and guide the development of diamond samples, as well as offering protocols for optimized sensing. 

Understanding the Linewidth of the ESR Spectrum Detected by a Single NV Center in Diamond 

B. Fortman and S. Takahashi, J. Phys. Chem. A 123, 6350-6355 (2019)

Spectral analysis of electron spin resonance (ESR) is a powerful technique for various investigations including characterization of spin systems, measurements of spin concentration, and probing spin dynamics. The nitrogen-vacancy (NV) center in diamond is a promising magnetic sensor enabling improvement of ESR sensitivity to the level of a single spin. Therefore, understanding the nature of NV-detected ESR (NV-ESR) spectrum is critical for applications to nanoscale ESR. Within this work we investigate the linewidth of NV-ESR from single substitutional nitrogen centers (called P1 centers). NV-ESR is detected by a double electron-electron resonance (DEER) technique. By studying the dependence of the DEER excitation bandwidth on NV-ESR linewidth, we find that the spectral resolution is improved significantly and eventually limited by inhomogeneous broadening of the detected P1 ESR. Moreover, we show that the NV-ESR linewidth can be as narrow as 0.3 MHz.  

Investigation of Near-Surface Defects of Nanodiamonds by High-Frequency EPR and DFT Calculation 

Z. Peng, T. Biktagirov, F. H. Cho, U. Gerstmann and S. Takahashi

J. Chem. Phys. 150 , 134702 (2019) 

Nanodiamonds (NDs) hosting nitrogen-vacancy (NV) centers are a promising platform for quantum sensing applications. Sensitivity of the applications using NV centers in NDs is often limited due to the presence of paramagnetic impurity contents near the ND surface. Here, we investigate near-surface paramagnetic impurities in NDs. Using high-frequency (HF) electron paramagnetic resonance spectroscopy, the near-surface paramagnetic impurity within the shell of NDs is probed and its g-value is determined to be 2.0028(3). Furthermore, HF electron-electron double resonance-detected nuclear magnetic resonance spectroscopy and a first principles calculation show that a possible structure of the near-surface impurity is the negatively charged vacancy V?. The identification of the near-surface impurity by the present investigation provides a promising pathway to improve the NV properties in NDs and the NV-based sensing techniques. 


Anton B. Burg Foundation 

Zumberge Research Fund

Contact information

Takahashi lab

Department of Chemistry

840 Downey Way, Stabler Hall

University of Southern California

Los Angeles, CA 90089-0744 

susumuta at usc dot edu