Floquet engineering in superconducting circuits: from arbitrary spin-spin interactions to the Kitaev honeycomb model

We derive a theory for the generation of arbitrary spin-spin interactions in superconducting circuits via periodic time modulation of the individual qubits or the qubit-qubit interactions. The modulation frequencies in our approach are in the microwave or radio frequency regime so that the required fields can be generated with standard generators. Among others, our approach is suitable for generating spin lattices that exhibit quantum spin liquid behavior such as Kitaev's honeycomb model.Comment: 21 pages, 9 figure

Quantum simulation with periodically driven superconducting circuits

Superconducting quantum circuits have made tremendous advances in realizing engineered quantum dynamics for quantum simulation and quantum information processing over the past two decades. Technological developments in the field of superconducting circuits have raised them to be the leading platform for implementing many-qubit systems. This thesis introduces a sequence of concepts for engineering spin-lattice Hamiltonians in analog quantum simulation with superconducting circuits. Our approach to quantum simulation is to engineer driving schemes that lead to implementations of the desired models. The applications of this approach are in our work mainly centered around two types of systems: interesting many-body topological quantum systems, namely Kitaev’s toric code and honeycomb model and two-body systems that can be employed as building blocks of larger quantum simulators or quantum computers. In the first part of this thesis, we make a proposal for an analog implementation of the toric code in superconducting circuits. We also discuss a realistic implementation of this model on an eight qubit lattice. In the second part, we present our analog approach for implementing arbitrary spinspin interactions in linearly and nonlinearly coupled superconducting qubits. Our proposed toolbox has the potential of easy generalization to a variety of systems and interactions. Lastly, based on our two-body toolbox, we set forward two possible implementations of the Kitaev honeycomb model and show that the engineered two-body interactions work - with good accuracy - in this many-body model

Multi-Module G2P Converter for Persian Focusing on Relations between Words

In this paper, we investigate the application of end-to-end and multi-module frameworks for G2P conversion for the Persian language. The results demonstrate that our proposed multi-module G2P system outperforms our end-to-end systems in terms of accuracy and speed. The system consists of a pronunciation dictionary as our look-up table, along with separate models to handle homographs, OOVs and ezafe in Persian created using GRU and Transformer architectures. The system is sequence-level rather than word-level, which allows it to effectively capture the unwritten relations between words (cross-word information) necessary for homograph disambiguation and ezafe recognition without the need for any pre-processing. After evaluation, our system achieved a 94.48% word-level accuracy, outperforming the previous G2P systems for Persian.Comment: 10 pages, 4 figure

Superconducting quantum simulator for topological order and the toric code

Topological order is now being established as a central criterion for characterizing and classifying ground states of condensed matter systems and complements categorizations based on symmetries. Fractional quantum Hall systems and quantum spin liquids are receiving substantial interest because of their intriguing quantum correlations, their exotic excitations and prospects for protecting stored quantum information against errors. Here we show that the Hamiltonian of the central model of this class of systems, the Toric Code, can be directly implemented as an analog quantum simulator in lattices of superconducting circuits. The four-body interactions, which lie at its heart, are in our concept realized via Superconducting Quantum Interference Devices (SQUIDs) that are driven by a suitably oscillating flux bias. All physical qubits and coupling SQUIDs can be individually controlled with high precision. Topologically ordered states can be prepared via an adiabatic ramp of the stabilizer interactions. Strings of qubit operators, including the stabilizers and correlations along non-contractible loops, can be read out via a capacitive coupling to read-out resonators. Moreover, the available single qubit operations allow to create and propagate elementary excitations of the Toric Code and to verify their fractional statistics. The architecture we propose allows to implement a large variety of many-body interactions and thus provides a versatile analog quantum simulator for topological order and lattice gauge theories

Observation of the Crossover from Photon Ordering to Delocalization in Tunably Coupled Resonators

Networks of nonlinear resonators offer intriguing perspectives as quantum simulators for non-equilibrium many-body phases of driven-dissipative systems. Here, we employ photon correlation measurements to study the radiation fields emitted from a system of two superconducting resonators, coupled nonlinearly by a superconducting quantum interference device (SQUID). We apply a parametrically modulated magnetic flux to control the linear photon hopping rate between the two resonators and its ratio with the cross-Kerr rate. When increasing the hopping rate, we observe a crossover from an ordered to a delocalized state of photons. The presented coupling scheme is intrinsically robust to frequency disorder and may therefore prove useful for realizing larger-scale resonator arrays

17O NMR parameters of some substituted benzyl ethers components: Ab initio study

The 17O NMR chemical shielding tensors and chemical shift for a set of substituted benzyl ethers derivatives containing (methyl, ethyl, isopropyl, t-butyl, brome and lithium) have been calculated. The molecular structures were fully optimized using B3LYP/6-31G(d,p). The calculation of the 17O shielding tensors employed the GAUSSIAN 98 implementation of the gauge-including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6-31G (d,p), 6-31++G(d,p) and 6-311++G(d,p) basis set methods at density functional levels of theories (DFT). The values determined using the GIAO and CSGT were found to give a good agreement with the experimental chemical shielding

The theoretical study of effect of temperature on the physicochemical parameters for binary mixtures of vinyl acetate and benzyl acetate, +o-xylene, +m-xylene and +p-xylene

AbstractIn this work we used the Flory theory of liquid mixtures for determining the thermal parameters such as excess thermal expansion coefficients αE, and isothermal coefficient of pressure excess molar enthalpy (∂HmE/∂P)T,x, of the binary mixtures formed by vinyl acetate and benzyl acetate+o-xylene, or m-xylene, or p-xylene at (303.15 and 313.15)K. From these data the acoustical parameters such as available volume (Va), isothermal (K/), isobaric (K), and isochoric acoustical parameters (K//), isochoric temperature coefficient of the internal pressure (X), and Moelwyn-Hughes parameter (C1), have been calculated. The excess thermal expansion coefficient αE, for the binary mixtures of benzyl acetate+o-xylene and vinyl acetate+m-xylene are negative in x=0.2434 and x=0.9602, respectively, and positive for all mole fractions and increase with increasing temperatures from (303.15 and 313.15)K. The isothermal coefficient of pressure excess molar enthalpy, (∂HmE/∂P)T,x, for vinyl acetate+o-xylene, +p-xylene and benzyl acetate+m-xylene,+p-xylene are negative and decrease with increasing temperatures from (303.15 and 313.15)K. The isothermal coefficient of pressure excess molar enthalpy, (∂HmE/∂P)T,x, for a binary mixture of benzyl acetate+o-xylene is positive and increases with increasing temperatures from (303.15 and 313.15)K

Theoretical study of adsorption of CO gas on pristine and AsGa-doped (4, 4) armchair models of BPNTs

AbstractIn this research, we investigate and discuss the adsorption of carbon monoxide gas (CO) on the outside and inside surface of pristine and AsGa doped of (4, 4) armchair boron phosphide nanotubes (BPNTs). The structural, electrical parameters, NMR, NQR parameters and chemical reactivity of these compounds were compared using DFT-based descriptors such as global hardness, global softness, electrophilicity, electronic chemical potential, and electronegativity. The considerable changes in the adsorption energies, energy gap values, global hardness, and NMR parameters generated by doping AsGa and orientation of CO adsorption and show the high sensitivity of the electronic properties of BPNTs towards the adsorption of CO on its surface. The results of the adsorption energy suggest that the AsGa decorated BPNTs are good candidate for CO adsorption. The NMR and NQR parameters variations in the complex show a significant change in the presence of CO adsorption and AsGa-doped. The quantum molecular descriptors and molecular orbital energies of the complex show that the nanotube can absorb CO molecule in its pristine and AsGa-doped form, and that the AsGa-doped and adsorption on the outside surface of nanotube is more favorable than pristine model and inside surface