A Note on Weak Double Dividends

A weak double-dividend is the proposition that the welfare improvement from a tax reform, where environmental taxes are used to lower distorting taxes, must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion. A general consensus has emerged that the weak double-dividend is an uncontroversial idea. We show in this note that a weak double-dividend need not hold in a world with multiple distortions.environmental tax policy, second-best taxation, general equilibrium analysis

Enhanced energy relaxation process of quantum memory coupled with a superconducting qubit

For quantum information processing, each physical system has different advantage for the implementation and so hybrid systems to benefit from several systems would be able to provide a promising approach. One of the common hybrid approach is to combine a superconducting qubit as a controllable qubit and the other quantum system with a long coherence time as a memory qubit. The superconducting qubit allows us to have an excellent controllability of the quantum states and the memory qubit is capable of storing the information for a long time. By tuning the energy splitting between the superconducting qubit and the memory qubit, it is believed that one can realize a selective coupling between them. However, we have shown that this approach has a fundamental drawback concerning energy leakage from the memory qubit. The detuned superconducting qubit is usually affected by severe decoherence, and this causes an incoherent energy relaxation from the memory qubit to the superconducting qubit via the imperfect decoupling. We have also found that this energy transport can be interpreted as an appearance of anti quantum Zeno effect induced by the fluctuation in the superconducting qubit. We also discuss a possible solution to avoid such energy relaxation process, which is feasible with existing technology

Tax Distortions and Global Climate Policy

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first note that the weak double-dividend, the proposition that the welfare improvement from a tax reform where environmental taxes are used to lower distorting taxes must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion, need not hold in a world with multiple distortions. We then present a large-scale computable general equilibrium model of the world economy with distortionary taxation. We use this model to evaluate a number of policies to reduce carbon emissions. We find that the weak double dividend is not obtained in a number of European countries. Results also demonstrate the point that the interplay between carbon policies and pre-existing taxes can differ markedly across countries. Thus one must be cautious in extrapolating the results from a country specific analysis to other countries.

Tax Distortions and Global Climate Policy

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first note that the weak double-dividend, the proposition that the welfare improvement from a tax reform where environmental taxes are used to lower distorting taxes must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion, need not hold in a world with multiple distortions. We then present a large-scale computable general equilibrium model of the world economy with distortionary taxation. We use this model to evaluate a number of policies to reduce carbon emissions. We find that the weak double dividend is not obtained in a number of European countries. Results also demonstrate the point that the interplay between carbon policies and pre-existing taxes can differ markedly across countries. Thus one must be cautious in extrapolating the results from a country specific analysis to other countries.

Optical Lenses for Atomic Beams

Superpositions of paraxial laser beam modes to generate atom-optical lenses based on the optical dipole force are investigated theoretically. Thin, wide, parabolic, cylindrical and circular atom lenses with numerical apertures much greater than those reported in the literature to date can be synthesized. This superposition approach promises to make high quality atom beam imaging and nano-deposition feasible.Comment: 10 figure

Spatiotemporal dynamics of quantum jumps with Rydberg atoms

We study the nonequilibrium dynamics of quantum jumps in a one-dimensional chain of atoms. Each atom is driven on a strong transition to a short-lived state and on a weak transition to a metastable state. We choose the metastable state to be a Rydberg state so that when an atom jumps to the Rydberg state, it inhibits or enhances jumps in the neighboring atoms. This leads to rich spatiotemporal dynamics that are visible in the fluorescence of the strong transition.Comment: 10 page

Initializing a Quantum Register from Mott Insulator States in Optical Lattices

We propose and quantitatively develop two schemes to quickly and accurately generate a stable initial configuration of neutral atoms in optical microtraps by extraction from the Mott insulator state in optical lattices. We show that thousands of atoms may be extracted and stored in the ground states of optical microtrap arrays with one atom per trap in one operational process demonstrating massive scalability. The failure probability during extraction in the first scheme can be made sufficiently small (10^{-4}) to initialize a large scale quantum register with high fidelity. A complementary faster scheme with more extracted atoms but lower fidelity is also developed.Comment: 5 pages, 3 figure