David Long

All Publications

• Interacting quasiperiodic spin chains in the prethermal regime PHYSICAL REVIEW B Tu, Y., Long, D. M., Sarma, S. 2024; 109 (21)

  View details for DOI 10.1103/PhysRevB.109.214309

  View details for Web of Science ID 001269492900002

• Edge theories for anyon condensation phase transitions PHYSICAL REVIEW B Long, D. M., Doherty, A. C. 2024; 109 (7)

  View details for DOI 10.1103/PhysRevB.109.075140

  View details for Web of Science ID 001198622700001

• Beyond Fermi's golden rule with the statistical Jacobi approximation SCIPOST PHYSICS Long, D. M., Hahn, D., Bukov, M., Chandran, A. 2023; 15 (6)

  View details for Web of Science ID 001132921100001

• Phenomenology of the Prethermal Many-Body Localized Regime PHYSICAL REVIEW LETTERS Long, D. M., Crowley, P. D., Khemani, V., Chandran, A. 2023; 131 (10): 106301

  Abstract

  The dynamical phase diagram of interacting disordered systems has seen substantial revision over the past few years. Theory must now account for a large prethermal many-body localized regime in which thermalization is extremely slow, but not completely arrested. We derive a quantitative description of these dynamics in short-ranged one-dimensional systems using a model of successive many-body resonances. The model explains the decay timescale of mean autocorrelators, the functional form of the decay-a stretched exponential-and relates the value of the stretch exponent to the broad distribution of resonance timescales. The Jacobi method of matrix diagonalization provides numerical access to this distribution, as well as a conceptual framework for our analysis. The resonance model correctly predicts the stretch exponents for several models in the literature. Successive resonances may also underlie slow thermalization in strongly disordered systems in higher dimensions, or with long-range interactions.

  View details for DOI 10.1103/PhysRevLett.131.106301

  View details for Web of Science ID 001154019600009

  View details for PubMedID 37739351

• Integrability and quench dynamics in the spin-1 central spin XX model SCIPOST PHYSICS Tang, L., Long, D. M., Polkovnikov, A., Chandran, A., Claeys, P. W. 2023; 15 (1)

  View details for DOI 10.21468/SciPostPhys.15.1.030

  View details for Web of Science ID 001041622600002

• Coupled layer construction for synthetic Hall effects in driven systems PHYSICAL REVIEW B Long, D. M., Crowley, P. D., Chandran, A. 2022; 106 (14)

  View details for DOI 10.1103/PhysRevB.106.144203

  View details for Web of Science ID 000877981400003

• Boosting the Quantum State of a Cavity with Floquet Driving. Physical review letters Long, D. M., Crowley, P. J., Kollár, A. J., Chandran, A. 2022; 128 (18): 183602

  Abstract

  The striking nonlinear effects exhibited by cavity QED systems make them a powerful tool in modern condensed matter and atomic physics. A recently discovered example is the quantized pumping of energy into a cavity by a strongly coupled, periodically driven spin. We uncover a remarkable feature of these energy pumps: they coherently translate, or boost, a quantum state of the cavity in the Fock basis. Current optical cavity and circuit QED experiments can realize the required Hamiltonian in a rotating frame. Boosting thus enables the preparation of highly excited nonclassical cavity states in near-term experiments.

  View details for DOI 10.1103/PhysRevLett.128.183602

  View details for PubMedID 35594101

• Many-body localization with quasiperiodic driving PHYSICAL REVIEW B Long, D. M., Crowley, P. D., Chandran, A. 2022; 105 (14)

  View details for DOI 10.1103/PhysRevB.105.144204

  View details for Web of Science ID 000804064800002

• Nonadiabatic Topological Energy Pumps with Quasiperiodic Driving. Physical review letters Long, D. M., Crowley, P. J., Chandran, A. 2021; 126 (10): 106805

  Abstract

  We derive a topological classification of the steady states of d-dimensional lattice models driven by D incommensurate tones. Mapping to a unifying (d+D)-dimensional localized model in frequency space reveals anomalous localized topological phases (ALTPs) with no static analog. While the formal classification is determined by d+D, the observable signatures of each ALTP depend on the spatial dimension d. For each d, with d+D=3, we identify a quantized circulating current and corresponding topological edge states. The edge states for a driven wire (d=1) function as a quantized, nonadiabatic energy pump between the drives. We design concrete models of quasiperiodically driven qubits and wires that achieve ALTPs of several topological classes. Our results provide a route to experimentally access higher dimensional ALTPs in driven low-dimensional systems.

  View details for DOI 10.1103/PhysRevLett.126.106805

  View details for PubMedID 33784118

• Comparing Experiments to the Fault-Tolerance Threshold. Physical review letters Kueng, R., Long, D. M., Doherty, A. C., Flammia, S. T. 2016; 117 (17): 170502

  Abstract

  Achieving error rates that meet or exceed the fault-tolerance threshold is a central goal for quantum computing experiments, and measuring these error rates using randomized benchmarking is now routine. However, direct comparison between measured error rates and thresholds is complicated by the fact that benchmarking estimates average error rates while thresholds reflect worst-case behavior when a gate is used as part of a large computation. These two measures of error can differ by orders of magnitude in the regime of interest. Here we facilitate comparison between the experimentally accessible average error rates and the worst-case quantities that arise in current threshold theorems by deriving relations between the two for a variety of physical noise sources. Our results indicate that it is coherent errors that lead to an enormous mismatch between average and worst case, and we quantify how well these errors must be controlled to ensure fair comparison between average error probabilities and fault-tolerance thresholds.

  View details for DOI 10.1103/PhysRevLett.117.170502

  View details for PubMedID 27824464

• Unitarisation of EFT amplitudes for dark matter searches at the LHC JOURNAL OF HIGH ENERGY PHYSICS Bell, N. F., Busoni, G., Kobakhidze, A., Long, D. M., Schmidt, M. A. 2016

  View details for DOI 10.1007/JHEP08(2016)125

  View details for Web of Science ID 000391784100001