Fall 2021

Abstract: Studying the effect of local projective measurements on the scaling of entanglement entropy is an intense topic of research in the context of measurement-induced phase transitions. While it is traditionally studied in discrete circuit models, a close continuous-time analogy can be drawn with monitored open quantum dynamics, where a record of the registered quantum-jump clicks allows one to reconstruct the pure-state stochastic trajectories.

Abstract: The paradigm of reservoir computing exploits the nonlinear dynamics of a physical reservoir to perform complex time-series processing tasks such as speech recognition and forecasting. Unlike other machine-learning approaches, reservoir computing relaxes the need for optimization of intra-network parameters, and is thus particularly attractive for near-term hardware-efficient quantum implementations.

Abstract: New experimental methods such as nitrogen vacancy center magnetometry allow for the imaging of local transport phenomena well below the micron length scale. I will describe how these methods might be used to experimentally reveal quantum critical dynamics which is invisible in conventional bulk transport measurements. Using a holographic system as a toy model, I will describe what happens as current is pushed through a geometric constriction in both hydrodynamic and quantum critical transport regimes, both in charge neutral and non-zero density limits.

Abstract: In cavity quantum electrodynamics (cavity QED) systems, the realization of strong coupling between light and atoms plays a critical role in studying quantum optics and entanglement.  At the same time, the Rydberg atom arrays provide a promising platform for exploring many-body physics. However, with the Rydberg-mediated interactions, the atoms mainly interact with each other locally. Combining the cavity QED and Rydberg arrays systems opens up new research directions in many-body physics with long-range interactions, creating a fully connected quantum network.

Abstract: Ultracold atomic gases have proven to provide valuable platforms to simulate quantum systems arising in disparate areas of physics. Polarons are well-studied quasiparticles in solid-state systems that describe an electron dressed by lattice distortions. The so-called Frohlich model is the typical starting point for theoretically describing such systems. More recently, polarons arising in Bose-Einstein condensates have been the focus of much attention, both theoretical and experimental.

Quantum process tomography is a critical capability for building quantum computers, enabling quantum networks, and understanding quantum sensors. Like quantum state tomography, the process tomography of an arbitrary quantum channel requires a number of measurements that scale exponentially in the number of quantum bits affected. However, the recent field of shadow tomography, applied to quantum states, has demonstrated the ability to extract key information about a state with only polynomially many measurements.

What does it mean to simulate a quantum field theory? This is a challenging question because a majority of the quantum field theories relevant to fundamental physics lack a fully rigourous mathematical definition. Thus it is impossible in general to compare the predictions of discretised theories with their continuum counterparts.

Theoretical models of quantum computation usually assume that 2-qubit gates can be performed between arbitrary pairs of qubits. However, in practice, scalable quantum architectures have qubit connectivity constraints, which can introduce polynomial depth overheads. Compiling quantum algorithms to work on scalable architectures therefore requires optimizing arrangements of gates and qubits to minimize these overheads.

In this special Friday Quantum Seminar, Dr. Allyson O'Brien, a Quantum Technology Scientist at Leidos, will share stories from her career path and a broader perspective on the field.

Pizza and drinks served after the talk.