Spring 2023

Abstract: Light is essential for life as we know it, and the ubiquitous PN-junction is the pervasive light sensor, whether for optical detection or for energy harvesting. Since its inception over 70 years ago, the physics behind the photodiode is now well understood, including its dependence on the illumination wavelength. However, there is a further prominent feature of photodiodes that has been largely overlooked. These devices can exhibit significant and tunable chromatic dispersion, which we call Optoelectronic Chromatic Dispersion (OED).

Abstract: How hard is it to compress a quantum state? To fast-forward the evolution of a local Hamiltonian? To unscramble the Hawking radiation of a black hole? Traditional complexity theory -- which is centered around decision problems and tasks with classical inputs and outputs -- appears inadequate for reasoning about the complexity of such tasks involving quantum inputs and outputs.

Abstract: Neutral atoms have emerged as a competitive platform for digital quantum simulations and computing. In this talk, we discuss recent results on the design of time-optimal and robust multi-qubit gates for neutral atoms. We present a family of Rydberg blockade gates that are robust against two common experimental imperfections -- intensity inhomogeneity and Doppler shifts – and demonstrate that these gates outperform existing gates for moderate or large imperfections.

Abstract: The postulates of quantum mechanics generalize classical probability distributions and thus transmission of information, enabling fundamentally novel protocols for communication and cryptography.  These algorithms motivate the deployment of quantum networks, a distributed model of computation where universality and fault-tolerance are often not required. Based on constructions from communication complexity, we design a voting scheme with efficient scaling of quantum communication and computation, and prove its security.

Abstract: Quantum dots are a promising platform to realize practical quantum computing. However, before they can be used as qubits, quantum dots must be carefully tuned to the correct regime in the voltage space to trap individual electrons. Moreover, realizable quantum computing requires tuning of large arrays, which translates to a significant increase in the number of parameters that need to be controlled and calibrated. This necessitates the development of robust and automated methods to bring the device into an operational state.

Dissertation Committee Chair: Maissam Barkeshli

Committee: 

In this talk, Dr Bermúdez will start by reviewing the recent progress of analog quantum simulators based on crystals of trapped atomic ions. He will discuss recent experiments that exploit both the electronic and vibrational degrees of freedom to simulate spin models and bosonic lattice models.

Dissertation Committee Chair:  Peter Shawhan

Committee: 

Jacob M. Taylor, Co-Chair 

Daniel Carney

Abstract: Classical algorithms are often not effective for solving nonconvex optimization problems where local minima are separated by high barriers. In this paper, we explore possible quantum speedups for nonconvex optimization by leveraging the global effect of quantum tunneling. Specifically, we introduce a quantum algorithm termed the quantum tunneling walk (QTW) and apply it to nonconvex problems where local minima are approximately global minima.

Dissertation Committee Chair: Professor Zohreh Davoudi

Committee: 

Professor Alexey Gorshkov, Advisor, Co-chair

Professor Andrew Childs, Dean’s Representative

Professor Alicia Kollar

Professor Nathan Schine