Simulating molecules on a cloud-based 5-qubit IBM-Q universal quantum computer
Communications Physics Nature Research 20 (2021)
Abstract:
Simulating the behaviour of complex quantum systems is impossible on classical supercomputers due to the exponential scaling of the number of quantum states with the number of particles in the simulated system. Quantum computers aim to break through this limit by using one quantum system to simulate another quantum system. Although in their infancy, they are a promising tool for applied fields seeking to simulate quantum interactions in complex atomic and molecular structures. Here we show an efficient technique for transpiling the unitary evolution of quantum systems into the language of universal quantum computation using the IBM quantum computer and show that it is a viable tool for compiling near-term quantum simulation algorithms. We develop code that decomposes arbitrary 3-qubit gates and implement it in a quantum simulation first for a linear ordered chain to highlight the generality of the approach, and second, for a complex molecule. Here we choose the Fenna-Matthews-Olsen (FMO) photosynthetic protein because it has a well characterised Hamiltonian and presents a complex dissipative system coupled to a noisy environment that helps to improve the efficiency of energy transport. The method can be implemented in a broad range of molecular and other simulation settings.
Two-photon Laser-written Photoalignment Layers for Patterning Liquid Crystalline Conjugated Polymer Orientation
Advanced Functional Materials Wiley (2020)
Excitation and temperature dependence of the broad gain spectrum in GaAs/AlGaAs quantum rings
Applied Physics Letters AIP Publishing 117:21 (2020) 213101
Abstract:
We have employed a variable stripe length method in order to measure the optical gain of GaAs/AlGaAs quantum rings. Although the large lateral diameter of quantum rings (∼ 50 nm) with a few nm size distribution is expected to cause a small spectral inhomogeneity (∼ 1 %), a broad gain width (∼ 300 meV) was observed. This result was attributed to a variation of the vertical heights and variations in localized states that exhibit crescent shaped wavefunctions, whereby the energy levels are distributed over a broad spectral range. When the excitation intensity is decreased, irregular peaks appear in the gain spectrum gradually. Similar phenomena were also observed with increased temperature. We conclude that excited carriers in quantum rings are distributed stochastically at various localized states, and the population inversion is sensitive to excitation intensity and temperature.A measurable physical theory of hyper-correlations beyond quantum mechanics
Physica Scripta IOP Publishing 96:1 (2020) 015006
Abstract:
whose non-local character exceeds the bounds allowed by quantum mechanics. Motivated by our observation that an extension of the Schroedinger equation with non-linear terms is directly linked to a relaxation of Born's rule, an axiom of quantum mechanics, we derive a physical theory that accounts for such hyper-correlated states and modifies Born's rule. We model correlated particles with a generalized probability theory whose dynamics are described with a non-linear version of Schr\"odinger's equation and demonstrate how that deviates from the standard formulation of quantum mechanics in experimental probability-prediction. We show also that the violation of the Clauser-Horn-Shimony-Holt inequality, the amount of non-locality, is proportional to the degree of non-linearity, which can be experimentally tested.Highly efficient photoluminescence and lasing from hydroxide coated fully inorganic perovskite micro/nano-rods
Advanced Optical Materials Wiley 8:23 (2020) 2001235