Accurate numerical simulations of open quantum systems using spectral tensor trains.

Decoherence between qubits is a major bottleneck in quantum computations. Decoherence results from intrinsic quantum and thermal fluctuations as well as noise in the external fields that perform the measurement and preparation processes. With prescribed colored noise spectra for intrinsic and extrinsic noise, we present a numerical method, Quantum Accelerated Stochastic Propagator Evaluation (Q-ASPEN), to solve the time-dependent noise-averaged reduced density matrix in the presence of intrinsic and extrinsic noise.

Direct Numerical Solutions to Stochastic Differential Equations with Multiplicative Noise.

Inspired by path integral solutions to the quantum relaxation problem, we develop a numerical method to solve classical stochastic differential equations with multiplicative noise that avoids averaging over trajectories. To test the method, we simulate the dynamics of a classical oscillator multiplicatively coupled to non-Markovian noise. When accelerated using tensor factorization techniques, it accurately estimates the transition into the bifurcation regime of the oscillator and outperforms trajectory-averaging simulations with a computational cost that is orders of magnitude lower.

Unique Degradation Signatures of Organic Solar Cells with Nonfullerene Electron Acceptors.

We investigate the degradation phenomena of organic solar cells based on nonfullerene electron acceptors (NFA) using intensity-modulated photocurrent spectroscopy (IMPS). Devices composed of NIR absorbing blends of a polymer (PTB7) and NFA molecules (COi8DFIC) were operated in air for varying periods of time that display unusual degradation trends. Light aging (e.