Device engineering for scalable qubit platform

Engineering strongly interacting qubit cluster with uniformity is a key step towards realizing scalable quantum system for non-classical quantum enhanced sensing or quantum node-based qubit register. We use cutting-edge nano-fabrication technique to generate geometric structures on diamond to engineer scalable qubit platform 

Further reads :

Sub-10 nm precision engineering of solid-state defects via nanoscale aperture array mask T. Hwang*, J. Lee*, S-W. Jeon, et al., Nano Lett. 8, 1672-1679 (2022)

Bright nitrogen-vacancy centers in diamond inverted nanocones

S-W. Jeon*, J. Lee*, H. Jung, et al., ACS Photonics 10, 2739-2747 (2020)

Developing novel quantum metrology schemes

We use a single to ensemble defect qubits to sense magnetic field via quantum interference measurement. We develop a novel quantum sensing scheme, utilizing such as geometric phase or Hamiltonian engineering methods to improve the sensitivity and the spectral resolution of the sensing signal. Our goal is to adopt various quantum mechanical tools to realize quantum-enhanced sensing

Further reads : 

Geometric phase magnetometry using a solid-state spin in diamond K. Arai*, J. Lee*, C. Belthangady, D. R. Glenn, H. Zhang, R. L. Walsworth, Nature Communications 9, 4996 (2018)

High resolution magnetic resonance spectroscopy using solid-state spin sensor D. R. Glenn*, D. B. Bucher*, J. Lee, M. D. Lukin, H. Park, R. L. Walsworth, Nature 555, 351-354 (2018)

Quantum simulation and quantum information applications

The qubit platform provides a versatile tool for investigating quantum phenomena. It offers a multitude of well-controlled experimental degrees of freedom, making it a powerful quantum simulator for studying complex and dynamic Hamiltonian models in condensed matter systems. We use solid-state defect qubits to explore quantum simulators and quantum information applications at exotic conditions 

Further reads : 

Dressed-state control of effective dipolar interaction between strongly coupled solid-state spins J. Lee, T. Mamiko, A. Xu, E. Bauch, M. J. H. Ku, and R.L Walsworth, npj Quantum Inf. 9, 77 (2023)

Controllable tunability of a Chern number within the electronic-nuclear spin system in diamond J. Lee*, K. Arai*, H. Zhang, M. J. H. Ku, and R. L. Walsworth, npj Quantum Inf. 9, 66 (2023)

Quantum noise spectroscopy and studying error mitigation methods

Solid-state spin defect system contains variety of un-wanted paramagnetic spins, which limits the coherence time of the NV spin qubits. Using quantum mechanical tools, we study the origin of quantum bath noise, and develop a quantum control scheme to mitigate the identified noise. Collaboration with prof. Hosung Seo (Ajou Univ) and Dr. Seung-Woo Lee (KIST)

Further reads : 

Decoherence of nitrogen-vacancy spin ensembles in a nitrogen electron-nuclear spin bath in diamond H. Park*, J. Lee*, S. Han, S. Oh and H. Seo, npj Quantum Inf. 8, 95 (2022)

Machine learning inspired quantum circuit optimization

In NISQ era, with a small number of qubits, optimization of quantum circuits with large circuit depth is a crucial step towards demonstrating quantum supremacy. We investigate numerical and theoretical approach to develop quantum circuit gate optimization schemes using classical optimization or machine learning algorithms to maximize the fidelity of the quantum circuit performance

Further reads :

Coarse-grained quantum state tomography with optimal POVM construction D.  Jung, Y-W. Cho, Y. Kim†, and J. Lee†, Phys. Rev. Res. 7, 023224 (2025)