Seminar

Fundamental forces of nature are described by gauge theories, and the interactions of matter with gauge fields lead to intriguing phenomena like the confinement of quarks in quantum chromodynamics. Separating a confined quark-anti-quark pair incurs an energy cost that grows linearly with their separation, eventually leading to the production of additional particles by an effect that is called string-breaking. In this talk, I will discuss how similar phenomenology can be probed using Rydberg atom arrays.

Irreversible quantum computation requires thermodynamic work. In principle, one can often evade work costs by implementing reversible transformations. In practice, complexity---the difficulty of realizing a quantum process---poses an obstacle: a realistic agent can perform only a limited number of gates and so not every reversible transformation. Hence an agent, if unable to complete a task unitarily, may expend work on an irreversible process, such as erasure, to finish the job.

Superconducting circuits are at the forefront of quantum computing and quantum sensing technologies, where accurate modeling and simulation are crucial for understanding and optimizing their performance. In this dissertation, we study modeling techniques and novel device designs to advance these technologies, focusing on efficient simulations, direct velocity measurement, and nonreciprocal devices for quantum information processing.

In this session, we will break out into subgroups to work through the mathematics in the paper "Hidden-State Proofs of Quantumness" (https://arxiv.org/abs/2410.06368).

Each group will have at least one person with familiarity in cryptography familiarity to guide the process.

Participants should read the paper before the session, but are not expected to have grasped all of its concepts.

Experimental control over the strength and angular dependence of interactions between atoms is a key capability for advancing quantum technologies. Here, we use microwave dressing to manipulate and enhance Rydberg-Rydberg interactions in an atomic ensemble. By resonantly coupling opposite parity Rydberg states, we create eigenstates with first-order dipole-dipole interactions. We study the modification of the interactions by measuring the statistics of the light retrieved from the ensemble.

Quantum computing leverages the quantum properties of subatomic matter to enable algorithms to run faster than those possible on a regular computer. Quantum computers have become increasingly practical in recent years, with some small-scale machines available for public use. Quantum computing applications are largely dependent on the software that manipulates computations on the hardware. These applications rely on a variety of symbolic representations including quantum programs to describe and manipulate quantum information effectively.

Quantum mechanics is one of our most profound and successful theoretical frameworks for understanding the physical world. It continues to drive remarkable technological and theoretical breakthroughs, spanning computing, coding theory, cryptography, material science, and chemistry. In this talk, I will describe how the algorithmic lens has been pivotal in rigorously analyzing such quantum systems and revealed deeper structural properties that were previously inaccessible through traditional approaches.

Optomechanical detectors offer a highly sensitive method for measuring weak forces. By optically trapping these systems in high vacuum, one can drastically reduce environmental noise and achieve exquisite control over the detector’s center-of-mass motion, rotational degrees of freedom, and physical characteristics such as charge states. This level of isolation enables the detector’s noise to reach the quantum measurement regime, where the dominant noise source is the measurement process itself.

Whether or not a physical system will thermalize from an initial state has been a key question in modern condensed matter physics. Closely related questions are determining whether observables in these systems relax to stationary values, and what those values are. Using tools from computational complexity theory, we demonstrate that given a Hamiltonian on a finite-sized system, determining whether or not it thermalizes or relaxes to a given stationary value is computationally intractable, even for a quantum computer.

Quantum query complexity is a widely studied model for understanding the capabilities and limitations of quantum computers. In this dissertation, we aim to better understand this complexity measure with respect to many natural models that are not well-studied. In particular, we are interested in the following concrete questions.

1) How powerful are quantum computers that could make multiple queries in parallel relative to analogous classical computers?

2) Can there be a simple quantum algorithmic primitive that inherently combines quantum walks and quantum search?