Smooth and sharp complexity transitions in learning with bounded quantum memory
Abstract: Learning properties of unknown quantum systems or processes is of fundamental importance to the development of quantum technologies. While many learning algorithms require access to external ancillary qubits (referred to as quantum memory), the statistical complexity and experimental costs for these algorithms vary considerably due to different sizes of quantum memory. Here, we investigate the transitions for statistical complexity required for learning quantum data with bounded quantum memory.
Succinct Fermion Data Structures
Abstract: Many applications of quantum simulation require qubit representations of a fixed number of fermions (F) in a larger number of possible modes (M). Representing such states is possible with I := ⌈log(M choose F)⌉ qubits, but existing constructions achieving this level of compactness result in fermion operators with gate complexity exponential in I. We show that a small amount of redundancy enables efficiency, presenting a second quantized fermion encoding using I + O( F ) qubits such that fermion operators can be implemented in depth O( log M ) and gate complexity O(I).
Novel tweezer-assisted sub-Doppler cooling of a 171Yb+ trapped ion crystal
Abstract: We propose a new sub-Doppler cooling scheme in trapped ion crystals in Paul traps which utilizes a Sisyphus-like cooling mechanism to simultaneously cool all the motional modes of the crystal. We use a hollow tweezer, tuned near resonance with the transition from the qubit manifold to a short-lived excited manifold, to generate a state-dependent tweezer potential. This tweezer also introduces a position dependent quench rate for the qubit states.
Some Unexpected Applications of Analog Quantum Computers
Abstract: Demonstrations of quantum advantage for random circuit and boson sampling over the past few years have generated considerable excitement for the future of quantum computing and has further spurred the development of a wide range of gate-based digital quantum computers, which represent quantum programs as a sequence of quantum gates acting on one and two qubits.
Aspects of Unconventional Transport and Quasiparticle in Condensed Matter Systems
Dissertation Committee Chair: Jay Sau
Committee:
Steven Anlage
Christopher Jarzynski
Johnpierre Paglione
Victor Yakovenko
Fast scrambling transitions and their applications in quantum simulators
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.
Giant Artificial Atoms and Molecules: Chiral (Directional) Photon Emission via Waveguide QED
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.
Fundamental Physics and Quantum Science with Polyatomic Molecules
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.
Hamiltonian engineering of spin-orbit–coupled fermions in an optical lattice clock
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.
Probing critical states of matter on a quantum computer
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.