Research

Condensed Matter Theory

We investigate (1) systems displaying non-trivial band topology or topological order and (2) low-dimensional quantum liquids, particularly in one dimension. These systems are fundamentally different from everyday materials and exhibit a beautiful array of exotic phenomena. To study these systems is to get a glimpse of universes dramatically different from our own, complete with their own physical laws and elementary particles. This work also finds practical applications in a diverse set of areas including quantum information, nanotechnology, nanophotonics, and even astrophysics.

Laser light has a high degree of coherence. Our work seeks to use light emitted from condensed matter systems as a probe of quantum coherence.

Light-Matter Interactions

Light is one of the most important ways that we observe our universe. Our study of light-matter interactions focuses on how quantum information is encoded in the light that condensed matter systems emit. Our work in this area has applications to quantum wires and the atmospheres of neutron stars.

Selected Publications

[1] W. DeGottardi, M. J. Gullans, Suraj Hegde, S. Vishveshwara, M. Hafezi, "Thermal radiation as a probe of one-dimensional electron liquids," Phys. Rev. B 99, 235124 (2019).

[2] A. Seif, W. DeGottardi, K. Balram, K. Esfarjani, and M. Hafezi, "Thermal management and non-reciprocal control of phonon flow via optomechanics", Nature Communications 9, 1207 (2018).

[3] Z.-P. Cian, G. Zhu, S.-K. Chu, A. Seif, W. DeGottardi, L. Jiang, and Mohammad Hafezi, "Photon pair condensation by engineered dissipation", Phys. Rev. Lett. 123, 063602 (2019).

[4] V. Bradley, K. Sharma, M. Hafezi, Wade DeGottardi, "Quantum Wire Coupled to Light," PRX Quantum 5, 040338 (2024).

Viscous forces arise from electron relaxation processes in a two-band quantum wire.

Gases and Liquids of One-Dimensional Fermions

One-dimensional Fermi gases and liquids represent an important case where Landau's Fermi liquid theory fails to apply. Instead of excitations described by electron-like quasiparticles, these systems display unusual properties. For instance, these systems manifest spin-charge separation, a phenomena in which charge and spin degrees of freedom can move independently of each other. Our work focuses on out-of-equilibrium behavior of these systems as that is typically what observed in experiments. We also study novel experimental setups which would offer 'smoking gun' evidence of exotic quantum behavior. Physical systems of interest include quantum wires, carbon nanotubes, cold atomic gases, and molecular chains at the surface of neutron stars.

Selected Publications

[5] W. DeGottardi and K. A. Matveev, "Viscous Properties of a Degenerate One-Dimensional Fermi Gas", Phys. Rev. Lett. 125, 076601 (2019).

[6] W. DeGottardi, "Viscous dissipation in a gas of one-dimensional fermions with generic dispersion", Phys. Rev. B 107, 075442 (2023).

Topological Phases of Matter

The discovery that certain phases of matter may be described by their topological properties rather than any local order parameter has revolutionized the field of condensed matter. Given that topological phases of matter are select, our work focuses on the physics of engineered systems. One system of considerable interest is a one-dimensional p-wave superconductor which have Majorana fermions at its edges. Work on photonic topological insulators investigates the nature of edge states and explores how they may be used as a robust conduit of quantum information.

Selected Publications

[7] S. Mittal, W. DeGottardi, and M. Hafezi, "Topological Photonic Systems", Optics and Photonic News 29, 37 (2018).

[8] S. Barik, A. Karasahin, C. Flower, T. Cai, H. Miyake, W. DeGottardi, M. Hafezi, and Edo Waks, "A topological quantum optics interface," Science 359, 666-668 (2018).

[9] W. DeGottardi, "Topological insulating phases of non-Abelian anyonic chains," Phys. Rev. B 90, 075129 (2014).

[10] W. DeGottardi, M. Thakurathi, S. Vishveshwara, and D. Sen, "Majorana fermions in superconducting wires: effects of long-range hopping, broken time-reversal symmetry and potential landscapes," Phys. Rev. B 88, 165111 (2013).

[11] W. DeGottardi, D. Sen, S. Vishveshwara, "Topological phases, Majorana modes and quench dynamics in a spin ladder system", New J. Phys. 13, 065028 (2011).

Superconducting Quantum Circuits

Superconducting quantum circuits are arguably the leading contender in the race to build a quantum computer. The technology has progressed to the extent that large networks of qubits can be created with any desired connectivity. Our group is primarily interested in such systems as 'quantum systems on-demand'. In the past, exotic many-body quantum systems had to be discovered. We focus on proposing and studying circuit designs which exhibit quantum effects that are not seen in naturally occurring materials.

Selected Publications

[12J A. Grover, J. I. Basham, A. Marakov, S. M. Disseler, R. T. Hinkey, M. Khalil, Z. A. Stegen,T. Chamberlin, W. DeGottardi, D. J. Clarke, J. R. Medford, J. D. Strand, M. J. A. Stoutimore, S. Novikov, D. G. Ferguson, D. Lidar, K. M. Zick, A. J. Przybysz, "Fast, Lifetime-Preserving Readout for High-Coherence Quantum Annealers", PRX Quantum 1, 020314 (2020).

[13] K. Sharma and W. DeGottardi, "Measurement of Many-Body Quantum Correlations in Superconducting Circuits," arXiv:2406.1239 v2.

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