Spring 2022

Quantum memory will play an important role in quantum networks, notably as components in quantum repeaters. One promising technique for realizing broadband quantum memory, the atomic frequency comb (AFC) protocol, calls for a material with large inhomogeneous broadening and small homogeneous broadening: spectral-hole burning techniques can be used to prepare the absorption spectrum in a periodic pattern of narrow peaks (an AFC). A single photon, absorbed as a collective excitation, will be re-emitted after a time interval fixed by the AFC tooth spacing.

For quantum computers to achieve their promise, regardless of the qubit technology, significant improvements to both performance and scale are required.  Quantum-dot-based qubits in silicon have recently enjoyed dramatic advances in fabrication and control techniques.  The “exchange-only” modality is of particular interest, as it avoids control elements that are difficult to scale such as microwave fields, photonics, or ferromagnetic gradients.  In this control scheme, the entirety of quantum computation may be performed using only asynchronous, baseband voltage p

Abstract: Semiconductor moiré materials provide a physical realization of the Kane-Mele-Hubbard model for studies of the combined effects of non-trivial band topology and strong electronic correlations. In this talk, I will discuss the rich electronic phase diagram of the Kane-Mele-Hubbard model realized in AB-stacked MoTe2/WSe2 moiré bilayers.

Recent work has predicted that quenched near-integrable systems can exhibit dynamics associated with thermal, quantum, or purely non-equilibrium phase transitions, depending on the initial state [1]. Using a trapped-ion quantum simulator with intrinsic long-range interactions, we investigate collective non-equilibrium properties of critical fluctuations after quantum quenches.

Quantum complexity is a measure of the minimal number of elementary operations required to approximately prepare a given state or unitary channel. Recently this concept has found applications beyond quantum computing---in the classification of topological phases of matter and in the description of chaotic many-body systems. Furthermore, within the context of the AdS/CFT correspondence, it has been postulated that the complexity of a specific time-evolved many-body quantum state is sensitive to the long-time properties of AdS-black hole interiors.

We argue that all locality-preserving mappings between fermionic observables and Pauli matrices on a two-dimensional lattice can be generated from the exact bosonization (arXiv:1711.00515), whose gauge constraints project onto the subspace of the toric code with emergent fermions. Starting from the exact bosonization and applying Clifford finite-depth generalized local unitary (gLU) transformation, we can achieve all possible fermion-to-qubit mappings (up to the re-pairing of Majorana fermions).

Dirac Spin Liquids (DSLs) are gapless symmetric states in 2+1 dimensions with no magnetic order. They are featureless, yet interesting because their low energy physics is believed to be described by QED-3, an effective field theory in terms of gapless Dirac fermions coupled to an emergent U(1) gauge field. They also serve as a parent state for seemingly unrelated magnetically ordered states, where the ordered states arise from condensation of ``monopole excitations” of the DSL. Can such a description have experimentally observable consequences?

Dissertation Committee Chair: Sankar Das Sarma
Committee:
Maissam Barkeshli
Alicia Kollar
Jay Sau
Andrew Childs
Additional Note: As this defense involves a public presentation, we request that attendees wear N95/KN95 masks as per current campus guidance for classes

Dissertation Committee Chair: Vladimir Manucharyan
Committee: 
Richard Greene
Steven Anlage
Jay Deep Sau
Ichiro Takeuchi

Dissertation Committee Chair: Mohammad Hafezi
Committee: 
Glenn Solomon
Sunil Mittal
You Zhou
Oded Rabin