# Hwang Lee

#### Associate Professor of Physics

Ph.D., 1998 - Texas A&M University

Louisiana State University

Department of Physics & Astronomy

451 Nicholson Hall, Tower Dr.

Baton Rouge, LA 70803-4001

225-578-2365-Office

hwlee@phys.lsu.edu

**Quantum Science and Technologies Group**

### Research Interests

#### Quantum Optics/Quantum Information Processing

The primary focus is generation of non-classical states of radiation fields and their applications in precision measurements, quantum computing, and communication. Current interests include design of efficient single-photon sources and detectors, multi-photon entanglement, enhancement of nonlinear optical processes using atomic coherence, and single-photon quantum nondemolition measurements.

Optical interferometry provides one of the finest tools for precision measurement. Basically it is to determine the unknown phase difference, imprinted by the physical quantity of interest, between the two paths of light propagation. The maximum capability of the interferometer is limited by the inherent uncertainty imposed by quantum mechanics. If the input source of the interferometer is classical, such as the light from a laser, the phase sensitivity is limited by the so-called standard quantum limit (or the shot-noise limit, in a somewhat narrow sense). The newly emergent field of quantum metrology utilizes certain quantum effects, such as quantum coherence, quantum entanglement, and squeezing, to push the capability of the interferometer beyond the standard quantum limit. The improvement in the sensitivity from the shot-noise limit of 1/N scaling to the ultimate limit, the Heisenberg limit of 1/N (where N is the average of input number of photons, representing the intensity of light) means that the same sensitivity can be achieved with less number of photons-less optical power and less radiation-pressure noise. Such reduction of the light intensity at the same level of sensitivity and resolution will provide huge benefits for any interferometric precision measurement and remote sensing, and may provide crucial advances in biomedical sensing where light intensity is a critical restriction. We study quantum correlations input states of light, quantum state engineering to produce desired inputs, and output-measurement strategies for such quantum enhanced optical interferometers. We apply the results of theoretical and numerical analyses to design interferometer devices with such as two-mode squeezed state inputs and photodetectors that measure only the eveness/oddness of the number of photons without counting.

### Current and Select Publications

- Seshadreesan, KP; Kim S; Dowling JP; Lee, H, "Phase estimation at the quantum Cramer-Rao
bound via parity detection,"
*Physical Review A***87**, 043833 (2013). - Gard, BT; Cross, RM; Anisimov, PM; Lee, H; Dowling, JP, "Quantum random walks with
multiphoton interference and high-order correlation functions,"
*Journal of Optical Society of America B***30**, 1538 (2013). - Roy Bardhan B; Anisimov, PM; Gupta, MK; Brown KL, Jones, NC; Lee, H; Dowling, JP,
"Dynamical decoupling in optical fibers: Preserving polarization qubits from birefringent
dephasing,"
*Physical Review A***85**, 022340 (2012). - Seshadreesan, KP; Anisimov, PM; Lee, H; Dowling, JP, "Parity detection achieves the
Heisenberg limit in interferometry with coherent mixed with squeezed vacuum light,"
*New Journal of Physics***13**, 083026 (2011). - Chiruvelli, A; Lee, H, "Parity Measurement in Quantum Optical Metrology,"
*Journal of Modern Optics***58**, 945-953 (2011). - Plick, WN, Anisimov, PM; Dowling, JP; Lee, H; Agarwal, GS, "Parity detection in quantum
optical metrology without number-resolving detectors,"
*New Journal of Physics***12**, 113025 (2010). - Anisimov, PM; Raterman, GM; Chiruvelli, A; Plick, WN; Huver, SD; Lee, H; Dowling,
JP, "Quantum Metrology with Two-Mode Squeezed Vacuum: Parity Detection Beats the Heisenberg
Limit,"
*Physical Review Letters***104**, 103602 (2010). - Gao, Y; Wildfeuer, CF; Anisimov, PM; Luine J; Lee, H; Dowling, JP, "Super-Resolution
at the Shot-Noise Limit with Coherent States and Photon-Number-Resolving Detectors,"
*Journal of Optical Society of America B***27**, A170 (2010).