@article {3260, title = {On the stability of solutions to Schr{\"o}dinger{\textquoteright}s equation short of the adiabatic limit}, year = {2023}, month = {3/23/2023}, abstract = {

We prove an adiabatic theorem that applies at timescales short of the adiabatic limit. Our proof analyzes the stability of solutions to Schrodinger\&$\#$39;s equation under perturbation. We directly characterize cross-subspace effects of perturbation, which are typically significantly less than suggested by the perturbation\&$\#$39;s operator norm. This stability has numerous consequences: we can (1) find timescales where the solution of Schrodinger\&$\#$39;s equation converges to the ground state of a block, (2) lower bound the convergence to the global ground state by demonstrating convergence to some other known quantum state, (3) guarantee faster convergence than the standard adiabatic theorem when the ground state of the perturbed Hamiltonian (H) is close to that of the unperturbed H, and (4) bound tunneling effects in terms of the global spectral gap when H is {\textquoteleft}{\textquoteleft}stoquastic\&$\#$39;\&$\#$39; (a Z-matrix). Our results apply to quantum annealing protocols with faster convergence than usually guaranteed by a standard adiabatic theorem. Our upper and lower bounds demonstrate that at timescales short of the adiabatic limit, subspace dynamics can dominate over global dynamics. Thus, we see that convergence to particular target states can be understood as the result of otherwise local dynamics.

}, url = {https://arxiv.org/abs/2303.13478}, author = {Jacob Bringewatt and Michael Jarret and T. C. Mooney} } @article {3018, title = {Simultaneous Stoquasticity}, journal = {Phys. Rev. A}, volume = {105}, year = {2022}, month = {06/09/2022}, abstract = {

Stoquastic Hamiltonians play a role in the computational complexity of the local Hamiltonian problem as well as the study of classical simulability. In particular, stoquastic Hamiltonians can be straightforwardly simulated using Monte Carlo techniques. We address the question of whether two or more Hamiltonians may be made simultaneously stoquastic via a unitary transformation. This question has important implications for the complexity of simulating quantum annealing where quantum advantage is related to the stoquasticity of the Hamiltonians involved in the anneal. We find that for almost all problems no such unitary exists and show that the problem of determining the existence of such a unitary is equivalent to identifying if there is a solution to a system of polynomial (in)equalities in the matrix elements of the initial and transformed Hamiltonians. Solving such a system of equations is NP-hard. We highlight a geometric understanding of this problem in terms of a collection of generalized Bloch vectors.

}, keywords = {FOS: Physical sciences, Quantum Physics (quant-ph)}, doi = {https://doi.org/10.1103/PhysRevA.105.062601}, url = {https://arxiv.org/abs/2202.08863}, author = {Jacob Bringewatt and Brady, Lucas T.} } @article {2322, title = {Study of radon reduction in gases for rare event search experiments}, year = {2018}, abstract = {

The noble elements, argon and xenon, are frequently employed as the target and event detector for weakly interacting particles such as neutrinos and Dark Matter. For such rare processes, background radiation must be carefully minimized. Radon provides one of the most significant contaminants since it is an inevitable product of trace amounts of natural uranium. To design a purification system for reducing such contamination, the adsorption characteristics of radon in nitrogen, argon, and xenon carrier gases on various types of charcoals with different adsorbing properties and intrinsic radioactive purities have been studied in the temperature range of 190-295 K at flow rates of 0.5 and 2 standard liters per minute. Essential performance parameters for the various charcoals include the average breakthrough times (τ), dynamic adsorption coefficients (ka) and the number of theoretical stages (n). It is shown that the ka-values for radon in nitrogen, argon, and xenon increase as the temperature of the charcoal traps decreases, and that they are significantly larger in nitrogen and argon than in xenon gas due to adsorption saturation effects. It is found that, unlike in xenon, the dynamic adsorption coefficients for radon in nitrogen and argon strictly obey the Arrhenius law. The experimental results strongly indicate that nitric acid etched Saratech is the best candidate among all used charcoal brands. It allows reducing total radon concentration in the LZ liquid Xe detector to meet the ultimate goal in the search for Dark Matter.

}, doi = {https://doi.org/10.1016/j.nima.2018.06.076}, url = {https://arxiv.org/abs/1805.11306}, author = {K. Pushkin and C. Akerlof and D. Anbajagane and J. Armstrong and M. Arthurs and Jacob Bringewatt and T. Edberg and C. Hall and M. Lei and R. Raymond and M. Reh and D. Saini and A. Sander and J. Schaefer and D. Seymour and N. Swanson and Y. Wang and W. Lorenzon} }