Primary Research Area
- AMO / Quantum Physics
Professor Virginia Lorenz received her B.A. in physics magna cum laude and mathematics in 2001 and completed her Ph.D. in physics in 2007 at the University of Colorado at Boulder. Her thesis work focused on measuring and modelling the transition from reversible to irreversible dephasing of electronic coherence in dense atomic vapors.
From 2007-2009 Professor Lorenz was a postdoctoral researcher in the Department of Atomic and Laser Physics at the University of Oxford, where she worked on implementations of quantum memories in atomic and solid state systems. From 2009-2014, she was an assistant professor in the Department of Physics and Astronomy at the University of Delaware, performing research in the areas of photonic quantum state generation, single-photon-level spectroscopy, and optical magnetometry of spin-orbit interactions in heavy metal / ferromagnetic metal systems. She joined the Department of Physics at Illinois in January 2015.
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Professor Lorenz's research group performs experiments in three major areas: quantum optics, atomic and molecular spectroscopy, and optical magnetometry.
Photonic quantum state characterization and engineering
The ability to create and control quantum states of light is important for quantum computation and quantum communication applications. We are exploring the use of standard, commercially available polarization-maintaining fiber (PMF) as a simple source of photon-pairs. PMF is an efficient generator of photon pairs and its large birefringence yields a 60THz detuning of the photon' phase-matched wavelengths from the pump, thus almost eliminating contamination due to photons produced from Raman scattering, which is an issue in other types of fiber sources. The joint spectral properties of the photon pair can be tailored by an appropriate choice of pump bandwidth and fiber length. We are implementing a newly developed stimulated-emission-based scheme to measure joint properties of the photon-pairs.
Generation, storage and retrieval of THz bandwidth quantum states
An essential capability for quantum computation and quantum communication is the synchronization of multiple sub-device elements, which requires a so-called quantum memory to store and retrieve information carried by photons. We are applying an off-resonance Raman protocol in atomic barium vapor to store and retrieve THz bandwidth quantum states. The broad bandwidth of the involved fields permits the characterization and optimization of storage and retrieval using spectral shaping, and enables us to study the spectral properties of nonclassical correlations between the photons and the excitations in the atomic ensemble. Barium has a strong transition at the fortuitous wavelength of 1500 nm, meaning it can store telecom wavelength photons directly. We are characterizing the states that the memory stores and retrieves using new techniques based on stimulated emission.
Development of spectroscopic techniques to probe coherence dynamics
Quantum applications such as the photon-pair source and quantum memory described above utilize single-photon detection and coincidence counting to quantify correlations. These tools can in turn be used to understand the dynamics of the materials from which the photons are generated. From the spectroscopy perspective, the motivation is to understand complex systems such as molecular liquids, in which inhomogeneous broadening dominates and multiple states couple to each other, in order to harness the chemical dynamics. To that end, we are developing single-excitation, single-photon-level techniques to understanding the complex structural correlations and environmental conditions surrounding molecules in liquids. We are exploring the capabilities of transient coherent Raman scattering in measuring the dynamics of liquid mixtures and the possibilities for using coincidence detection to measure vibrational energy redistribution, a complex phenomenon due to the intricate couplings and variety of timescales involved.
Spin-orbit interaction driven phenomena in ferromagnetic / heavy metal bilayers
In the context of classical information storage and processing, spintronics, which uses the spin of the electron as an information carrier, holds promise for the creation of reliable, energy-efficient, easily scalable resources for next-generation computing. One method to manipulate electron spin is via the spin-orbit interaction, in which an electric current exerts a torque on the magnetization, and recently the implementation of spin-orbit-interaction induced switching in heavy metal (HM) / ferromagnetic metal (FM) bilayers has attracted great attention. Although beneficial effects have been successfully demonstrated, researchers are still debating the underlying principles, as to whether the dominating spin-orbit interaction (SOI) arises from the HM/FM interface due to the Rashba effect or from the bulk of the HM due to the spin Hall effect. We have developed a magneto-optic Kerr effect magnetometer that is capable of detecting SOI induced magnetization reorientation. Using this technique, we are studying and quantifying the bulk and interface contributions to spin-orbit interaction in a variety of materials.
Selected Articles in Journals
- B. Fang, M. Liscidini, J. E. Sipe, and V. O. Lorenz, "Multidimensional characterization of an entangled photon-pair source via stimulated emission tomography," Opt. Express 24, 10013-10019 (2016).
- B. Fang, O. Cohen, M. Liscidini, J. E. Sipe, and V. O. Lorenz, "Fast and highly resolved capture of the joint spectral density of photon pairs," Optica 1, 281-4 (2014).
- X. Fan, H. Celik, J. Wu, C. Ni, K.-J. Lee, V. O. Lorenz, J. Q. Xiao, "Quantifying interface and bulk contributions to spin-orbit torque in magnetic bilayers," Nature Communications 5, 3042 (2014).
- B. Fang, O. Cohen, J. B. Moreno, and V. O. Lorenz, "State engineering of photon pairs produced through dual-pump spontaneous four-wave mixing," Opt. Express 21, 2707-2717 (2013).
- K. F. Reim, J. Nunn, V. O. Lorenz, B. J. Sussman, K. C. Lee, N. K. Langford, D. Jaksch and I. A.Walmsley, "Towards high-speed optical quantum memories," Nature Photonics 4, 218-221 (2010).
- V. O. Lorenz, S. Mukamel, W. Zhuang and S. T. Cundiff, "Ultrafast Optical Spectroscopy of Spectral Fluctuations in a Dense Atomic Vapor," Phys. Rev. Lett. 100, 013603 (2008).
- V. O. Lorenz and S. T. Cundiff, "Non-Markovian Dynamics in a Dense Potassium Vapor," Phys. Rev. Lett. 95, 163601 (2005).