JQI

There is a rich connection between classical and quantum codes and holographic correspondence connecting 2d CFTs and abelian 3d Chern-Simons theories. In the 3d language the codes emerge as a way to parametrize condensable anyons. Upon condensation 3d topological field theory gives rise to 2d CFT at the boundary. This provides a way to construct 2d CFTs from codes - the so called "code CFTs." This construction of code CFT has a natural interpretation in terms of a CSS quantum code (defined in terms of the original classical code, defining the CFT).

I will discuss recent advances in improving and costing quantum algorithms for linear differential equations. I will introduce a stability-based analysis of Berry et al.’s 2017 algorithm that greatly extends its scope and leads to complexities sublinear in time in a broad range of settings – Hamiltonian simulation being a boundary case that prevents this kind of broad fast-forwarding. I illustrate these gains via toy examples such as the linearized Vlasov-Possion equation, networks of coupled, damped, forced harmonic oscillators and quadratic nonlinear systems of ODEs.

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.

Dissertation Committee Chair: Jay Sau

Committee: 

Steven Anlage

Christopher Jarzynski

Johnpierre Paglione

Victor Yakovenko

Abstract: In many-body systems of cold atoms and their applications to quantum metrology and quantum computing, there are important questions around how large an entangled many-body state we can usefully and reliably prepare in the presence of decoherence. Information spreading and entanglement growth are typically limited by Lieb-Robinson bounds, so that the useful system size with short-range interactions will grow only linearly with the coherence time.

Abstract: In this talk, we present a demonstration of “giant artificial atoms” realized with superconducting qubits in a waveguide QED architecture. The superconducting qubits couple to the waveguide at multiple, well-separated locations. In this configuration, the dipole approximation no longer holds, and the giant atom may quantum mechanically self-interfere. Multiple, interleaved qubits in this architecture can be switched between protected and emissive configurations, while retaining waveguide-mediated qubit-qubit interactions.

Abstract: Polyatomic molecules uniquely enable the simultaneous combination of multiple features advantageous for precision measurement and quantum science. Searches for fundamental symmetry violations benefit from large internal molecular fields, high polarizability, internal co-magnetometry, and the ability to cycle photons - all of which can be found in certain engineered polyatomic species. We discuss experimental and theoretical developments in several linear metal hydroxide (MOH) species, including spectroscopy, photon cycling, andquantum control.

Abstract: Harnessing the behavior of complex systems is at the heart of quantum technologies. Precisely engineered ultracold gases are emerging as a powerful tool for this task. In this talk I will explain how ultracold alkaline-earth atoms  (AEAs)  trapped by light used to create optical lattice clocks  are not only fascinating, but of crucial importance since they can help us to answer cutting-edge questions about complex many-body phenomena and magnetism.

Abstract: I will describe Quantinuum’s trapped ion QCCD quantum computers, with a particular focus on the key technical challenges and solutions for realizing mid-circuit measurement and reuse of qubits. In addition to the importance these capabilities play in quantum error correction, they also afford remarkable efficiencies in simulating many-body physics, enabling explorations of physics at length scales well beyond the limits that would be naively guessed from the size of present-day quantum computers.

Abstract: A quantum impulse is a brief but strong perturbation that produces a sudden change in a wavefunction.