Ph.D. Physics - University of Michigan, 2009
B.S. Physics - Michigan Technological University, 2004
Dr. Kestner was previously a postdoctoral researcher in the Condensed Matter Theory Center at the University of Maryland, College Park (2009-2012)
I am interested in developing useful physical devices that exploit the strange features of quantum mechanics. A prominent example is a quantum computer, which could solve a certain important class of problems exponentially faster than any computer based on the current classical bit model. My work is theoretical, and focuses on experimentally available systems that present distinctly quantum behavior: ultracold gases of atoms or polar molecules, and "artificial" atoms and molecules, i.e., quantum dot systems in solid state materials.
Ultracold gases of atoms or molecules trapped in optical lattices have been proposed as versatile quantum simulators: Many seminal models and concepts from condensed matter physics are difficult to treat rigorously, whether analytically or computationally, outside of a small region of parameter space where perturbation theories apply. Thus, we are often unable to reliably determine whether a given material is behaving in accordance with one of the idealized models, because we can not say what the model predicts in that parameter regime. Often, however, the underlying theoretical models can be cleanly realized in an optical lattice system, with several experimentally accessible parameters that can be tuned through a large range. Thus, a link may be established between condensed matter models and resulting physical phenomena. This program of research may prove invaluable towards understanding, and even engineering, exotic "quantum materials," such as high-Tc superconductors. However, this requires an accurate characterization of the precisely controlled atomic system and an appropriate design of the atomic experiment to map onto the desired model. I address these issues by performing analytical and numerical few-body and Hartree-Fock calculations in various cases to determine key features of the atomic behavior and by using these results to derive "effective Hamiltonians," showing how to configure the ultracold system to emulate various models.
My work on semiconductor quantum dots involves designing protocols to precisely control (despite a noisy environment) the spin state of one or more electrons trapped in the dots. This is an important problem, since electron spins in quantum dots can be used as building blocks in a quantum computer, and experiments are currently limited by spin dephasing. This is a common problem in many contexts (such as nuclear magnetic resonance) but the quantum dot system imposes very strict constraints on the control capabilities, ruling out the common solutions (such as BB1). Recently, my collaborators at the University of Maryland, College Park and I have found the first instance of a composite pulse sequence that self-corrects certain types of error believed to be the most relevant experimentally.
"Composite pulses for robust universal control of singlet-triplet qubits," Xin Wang, Lev S. Bishop, J. P. Kestner, Edwin Barnes, Kai Sun, and S. Das Sarma, Nat. Commun. 3, 997 (2012).
"Proposed spin qubit CNOT gate robust against noisy coupling," J. P. Kestner and S. Das Sarma, Phys. Rev. A 84, 012315 (2011).
"Prediction of a Novel Topological ``Haldane Liquid" Phase in One-Dimensional Cold Polar Molecular Lattice," J. P. Kestner, Bin Wang, Jay D. Sau, and S. Das Sarma, Phys. Rev. B 83, 174409 (2011).
"Effective single-band models for strongly interacting fermions in an optical lattice," J. P. Kestner and L.-M. Duan, Phys. Rev. A 81, 043618 (2010).
"Level crossing in the three-body problem for strongly interacting fermions in a harmonic trap," J. P. Kestner and L.-M. Duan, Phys. Rev. A 76, 033611 (2007).