# Harold U. Baranger

## Professor of Physics

###### Links

### Overview

The broad focus of Prof. Baranger's group is **quantum open systems at the nanoscale**, particularly the generation of **correlation** between particles in such systems. Fundamental interest in nanophysics-- the physics of small, nanometer scale, bits of solid-- stems from the ability to control and probe systems on length scales larger than atoms but small enough that the averaging inherent in bulk properties has not yet occurred. Using this ability, entirely unanticipated phenomena can be uncovered on the one hand, and the microscopic basis of bulk phenomena can be probed on the other. Additional interest comes from the many links between nanophysics and nanotechnology. Within this thematic area, our work ranges from projects trying to nail down realistic behavior in well-characterized systems, to more speculative projects reaching beyond regimes investigated experimentally to date.

Correlations between particles are a central issue in many areas of condensed matter physics, from emergent many-body phenomena in complex materials, to strong matter-light interactions in quantum information contexts, to transport properties of single molecules. Such correlations, for either electrons or bosons (photons, plasmons, phonons,…), underlie key phenomena in nanostructures. Using the exquisite control of nanostructures now possible, experimentalists will be able to engineer correlations in nanosystems in the near future. Of particular interest are cases in which one can tune the competition between different types of correlation, or in which correlation can be tunably enhanced or suppressed by other effects (such as confinement or interference), potentially causing a quantum phase transition-- a sudden, qualitative change in the correlations in the system.

My recent work has addressed correlations in both electronic systems (quantum wires and dots) and photonic systems (photon waveguides). We have focused on 3 different systems: (1) qubits coupled to a photonic waveguide, (2) quantum dots in a dissipative environment, and (3) low-density electron gas in a quantum wire. The methods used are both analytical and numerical, and are closely linked to experiments.

### Selected Grants

Quantum Phases in Nanosystems: Non-Equilibrium Phenomena Near Quantum Critical Points awarded by Department of Energy (Principal Investigator). 2010 to 2019

Waveguide QED: Photon Correlations in Strongly Coupled Open Systems awarded by National Science Foundation (Principal Investigator). 2011 to 2017

Enhancing Light-Matter Interfaces via Collective Self-Organization awarded by National Science Foundation (Co-Principal Investigator). 2012 to 2016

Development of dissipative resonant levels to study Majorana physics in nanotube quantum dots awarded by Army Research Office (Co-Principal Investigator). 2014 to 2015

Coherence and Correlations in Electronic Nanostructures awarded by National Science Foundation (Principal Investigator). 2005 to 2009

Collaborative Research: Is Resilient Quantum Computing in Solid State Systems Possible? awarded by National Science Foundation (Principal Investigator). 2005 to 2008

Coherence and Correlation in Electronic Nanostructures awarded by National Science Foundation (Principal Investigator). 2001 to 2006

Robustness of Quantum Computing in Quantum Dots awarded by Army Research Office (Principal Investigator). 2002 to 2005

Electronic Properties of Nanostructures awarded by National Science Foundation (Principal Investigator). 2002 to 2005

Novais, E, Mucciolo, ER, and Baranger, HU. "Hamiltonian methods in quantum error correction and fault tolerance." *Quantum Error Correction.* January 1, 2012. 585-611.
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Gheeraert, N, Zhang, XHH, Sépulcre, T, Bera, S, Roch, N, Baranger, HU, and Florens, S. "Particle production in ultrastrong-coupling waveguide QED." *Physical Review A* 98.4 (October 8, 2018).
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Fang, Y-LL, Ciccarello, F, and Baranger, HU. "Non-Markovian dynamics of a qubit due to single-photon scattering in a waveguide." *New Journal of Physics* 20.4 (April 1, 2018): 043035-043035.
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Zhang, XHH, and Baranger, HU. "Quantum interference and complex photon statistics in waveguide QED." *Physical Review A* 97.2 (February 2018).
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Zhang, XHH, and Baranger, HU. "Photon Statistics in a Waveguide: Beyond Bunching and Antibunching (Published online)." *arXiv* 1710 (October 2017).

Fang, Y-LL, and Baranger, HU. "Multiple emitters in a waveguide: Nonreciprocity and correlated photons at perfect elastic transmission." *Physical Review A* 96.1 (July 2017).
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Zhang, G, Novais, E, and Baranger, HU. "Rescuing a Quantum Phase Transition with Quantum Noise." *Physical Review Letters* 118.5 (February 2017).
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Zhang, G, Chung, C-H, Ke, CT, Lin, C-Y, Mebrahtu, H, Smirnov, AI, Finkelstein, G, and Baranger, HU. "Universal Nonequilibrium I-V Curve at an Interacting Impurity Quantum Critical Point (Published online)." *arXiv* 1609 (September 2016).

Fang, Y-LL, and Baranger, HU. "Reprint of : Photon correlations generated by inelastic scattering in a one-dimensional waveguide coupled to three-level systems." *Physica E: Low-dimensional Systems and Nanostructures* 82 (August 2016): 71-78.
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Fang, Y-LL, and Baranger, HU. "Photon correlations generated by inelastic scattering in a one-dimensional waveguide coupled to three-level systems." *Physica E: Low Dimensional Systems and Nanostructures* 78 (April 2016): 92-99.
Full Text Open Access Copy

Bera, S, Baranger, HU, and Florens, S. "Dynamics of a qubit in a high-impedance transmission line from a bath perspective." *Physical Review A* 93.3 (March 2016).
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## Pages

Usaj, G, and Baranger, HU. "TMR in nanoscale F-N-F systems: Mesoscopic fluctuations." 2001.

BARANGER, HU. "TRANSPORT IN ELECTRON WAVE-GUIDES - FILTERING AND BEND RESISTANCES." 1991.

DAVIES, JH, NIXON, JA, and BARANGER, HU. "POTENTIAL FLUCTUATIONS IN HETEROSTRUCTURE DEVICES." 1991.

BARANGER, HU, and STONE, AD. "SELECTIVE-POPULATION OF MODES IN ELECTRON WAVE-GUIDES - BEND RESISTANCES AND QUENCHING OF THE HALL RESISTANCE." 1990.