Spring 2024

Abstract: TBA

Abstract: The task of quantum position verification (QPV) deploys quantum information with the aim to use a party's position as a cryptographic credential. One well-studied proposed protocol for this task, f-routing, involves a mixture of classical information and a single quantum bit that has to be routed somewhere as a function of the classical information.

Dissertation Committee Chair: Steven Rolston

Committee: 

Alexey Gorshkov (co-chair)

Andrew Childs (Dean’s Representative)

Nathan Schine

Michael Gullans

Abstract: I will review the concept of Floquet quantum error-correcting codes, and, more generally, dynamic codes. These codes are defined through sequences of low-weight measurements that change the instantaneous code in time and enable error correction.  I will explain a few viewpoints on these codes, including state teleportation and anyon condensation, and will explain how to implement gates purely by adjusting the sequences of low-weight measurement.

Abstract: The concept of antidistinguishability of quantum states has been studied to investigate foundational questions in quantum mechanics. It is also called quantum state elimination, because the goal of such a protocol is to guess which state, among finitely many chosen at random, the system is not prepared in (that is, it can be thought of as the first step in a process of elimination). Antidistinguishability has been used to investigate the reality of quantum states, ruling out psi-epistemic ontological models of quantum mechanics [Pusey et al., Nat. Phys., 8(6):475-478, 2012].

Abstract:  Topological band structures are well known to produce symmetry-protected chiral edge states which transport particles unidirectionally. These same effects can be harnessed in the frequency domain using a spin-1/2 system subject to periodic drives.

Abstract: This talk will present our work on the observation of super-radiance in a cloud of cold atoms driven by a laser. We start from an elongated cloud of laser cooled atoms that we excite either perpendicularly or along its main axis. This situation bears some similarities with cavity quantum electrodynamics: here the cavity mode is replaced by the diffraction mode of the elongated cloud. We observe superradiant pulses of light after population inversion.

Abstract: A variety of quantum algorithms employ Pauli operators as a convenient basis for studying the spectrum or evolution of Hamiltonians or measuring multibody observables. One strategy to reduce circuit depth in such algorithms involves simultaneous diagonalization of Pauli operators generating unitary evolution operators or observables of interest. We propose an algorithm yielding quantum circuits with depths O(nlogr) diagonalizing n-qubit operators generated by r Pauli operators.

Abstract: Today’s programmable quantum simulators offer versatile platforms for exploring many-body phases and dynamics in correlated quantum systems. In this talk, we present some new—and surprising—insights into nonequilibrium quantum dynamics inspired by such recent experimental advances. First, we focus on understanding the evolution of closed quantum systems driven through a phase transition, which is crucial for quantum state preparation and adiabatic algorithms.

Abstract: Utilizing quantum mechanical effects such as entanglement can allow sensors to have sensitivities below those imposed on purely classical states. As an example, our experiment has utilized entanglement of the spin and collective motion of 2D crystals of over 100 ions in a Penning trap to demonstrate a sensitivity to displacements of 8.8 ± 0.4 decibels below the standard quantum limit [Science 373, 673 (2021)].