768 research outputs found
Biocatalytic Route to Chiral Precursors of β-Substituted-γ-Amino Acids
In this work, we utilized commercial lipases (from Thermomyces lanuginosa, Rhizopus delemar, and Mucor miehei) as biocatalysts for the efficient synthesis of precursors of β-substituted-γ-amino acids. This biocatalytic route provides a practical and efficient synthesis of a wide range of optically active compounds by accepting a number of aliphatic and aromatic 3-substituted-3-cyano-2-(ethoxycarbonyl)propanoic acid ethyl esters (2) without compromising enantioselectivity or yields. The resolution step allows for the nearly quantitative recovery of the unreacted enantiomer of R-(2) as well as the newly formed 3-substituted-3-cyano-2-(ethoxycarbonyl)propanoic acid (3) in high enantio and diastereoselectivity. The use of a facile thermal decarboxylation of (3) in aqueous solution to produce 3-substituted-3-cyanopropanoic acid ethyl esters (4) enable us to prepare a wide range of optically active precursors of β-Substituted-γ-Amino Acids
Analytic Solutions to Coherent Control of the Dirac Equation
A simple framework for Dirac spinors is developed that parametrizes
admissible quantum dynamics and also analytically constructs electromagnetic
fields, obeying Maxwell's equations, which yield a desired evolution. In
particular, we show how to achieve dispersionless rotation and translation of
wave packets. Additionally, this formalism can handle control interactions
beyond electromagnetic. This work reveals unexpected flexibility of the Dirac
equation for control applications, which may open new prospects for quantum
technologies
Dirac open quantum system dynamics: formulations and simulations
We present an open system interaction formalism for the Dirac equation.
Overcoming a complexity bottleneck of alternative formulations, our framework
enables efficient numerical simulations (utilizing a typical desktop) of
relativistic dynamics within the von Neumann density matrix and Wigner phase
space descriptions. Employing these instruments, we gain important insights
into the effect of quantum dephasing for relativistic systems in many branches
of physics. In particular, the conditions for robustness of Majorana spinors
against dephasing are established. Using the Klein paradox and tunneling as
examples, we show that quantum dephasing does not suppress negative energy
particle generation. Hence, the Klein dynamics is also robust to dephasing
Sampling-based learning control of inhomogeneous quantum ensembles
Compensation for parameter dispersion is a significant challenge for control
of inhomogeneous quantum ensembles. In this paper, we present a systematic
methodology of sampling-based learning control (SLC) for simultaneously
steering the members of inhomogeneous quantum ensembles to the same desired
state. The SLC method is employed for optimal control of the state-to-state
transition probability for inhomogeneous quantum ensembles of spins as well as
type atomic systems. The procedure involves the steps of (i) training
and (ii) testing. In the training step, a generalized system is constructed by
sampling members according to the distribution of inhomogeneous parameters
drawn from the ensemble. A gradient flow based learning and optimization
algorithm is adopted to find the control for the generalized system. In the
process of testing, a number of additional ensemble members are randomly
selected to evaluate the control performance. Numerical results are presented
showing the success of the SLC method.Comment: 8 pages, 9 figure
Quantum algorithms for the simulation of perturbative QCD processes
Quantum computers are expected to give major speed-ups for the simulation of
quantum systems. In these conference proceedings, we discuss quantum algorithms
for the simulation of perturbative Quantum Chromodynamics (QCD) processes. In
particular, we describe quantum circuits for simulating the colour part of the
interactions of quarks and gluons. We implement our circuits on a simulated
noiseless quantum computer and validate them by calculating colour factors for
various examples of Feynman diagrams.Comment: 10 pages, 1 figure. Contribution to the proceedings of RADCOR 202
Quantum simulation of colour in perturbative quantum chromodynamics
Quantum computers are expected to give major speed-ups for the simulation of
quantum systems. In this work, we present quantum gates that simulate the
colour part of the interactions of quarks and gluons in perturbative quantum
chromodynamics (QCD). As a first application, we implement these circuits on a
simulated noiseless quantum computer and use them to calculate colour factors
for various examples of Feynman diagrams. This work constitutes a first key
step towards a quantum simulation of generic scattering processes in
perturbative QCD.Comment: 20 pages, 11 figure
Sampling-based Learning Control for Quantum Systems with Uncertainties
Robust control design for quantum systems has been recognized as a key task
in the development of practical quantum technology. In this paper, we present a
systematic numerical methodology of sampling-based learning control (SLC) for
control design of quantum systems with uncertainties. The SLC method includes
two steps of "training" and "testing". In the training step, an augmented
system is constructed using artificial samples generated by sampling
uncertainty parameters according to a given distribution. A gradient flow based
learning algorithm is developed to find the control for the augmented system.
In the process of testing, a number of additional samples are tested to
evaluate the control performance where these samples are obtained through
sampling the uncertainty parameters according to a possible distribution. The
SLC method is applied to three significant examples of quantum robust control
including state preparation in a three-level quantum system, robust
entanglement generation in a two-qubit superconducting circuit and quantum
entanglement control in a two-atom system interacting with a quantized field in
a cavity. Numerical results demonstrate the effectiveness of the SLC approach
even when uncertainties are quite large, and show its potential for robust
control design of quantum systems.Comment: 11 pages, 9 figures, in press, IEEE Transactions on Control Systems
Technology, 201
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