Quantum bit string sealing

Though it was proven that secure quantum sealing of a single classical bit is impossible in principle, here we propose an unconditionally secure quantum sealing protocol which seals a classical bit string. Any reader can obtain each bit of the sealed string with an arbitrarily small error rate, while reading the string is detectable. The protocol is simple and easy to be implemented. The possibility of using this protocol to seal a single bit in practical is also discussed.Comment: Add a discussion on the possibility of sealing a single bit in practica

Generation of GHZ entangled states of photons in multiple cavities via a superconducting qutrit or an atom through resonant interaction

We propose an efficient method to generate a GHZ entangled state of n photons in n microwave cavities (or resonators) via resonant interaction to a single superconducting qutrit. The deployment of a qutrit, instead of a qubit, as the coupler enables us to use resonant interactions exclusively for all qutrit-cavity and qutrit-pulse operations. This unique approach significantly shortens the time of operation which is advantageous to reducing the adverse effects of qutrit decoherence and cavity decay on fidelity of the protocol. Furthermore, the protocol involves no measurement on either the state of qutrit or cavity photons. We also show that the protocol can be generalized to other systems by replacing the superconducting qutrit coupler with different types of physical qutrit, such as an atom in the case of cavity QED, to accomplish the same task.Comment: 11 pages, 5 figures, accepted by Phys. Rev.

Linear and nonlinear acoustic wave propagation in the atmosphere

The investigation of the acoustic wave propagation theory and numerical implementation for the situation of an isothermal atmosphere is described. A one-dimensional model to validate an asymptotic theory and a 3-D situation to relate to a realistic situation are considered. In addition, nonlinear wave propagation and the numerical treatment are included. It is known that the gravitational effects play a crucial role in the low frequency acoustic wave propagation. They propagate large distances and, as such, the numerical treatment of those problems become difficult in terms of posing boundary conditions which are valid for all frequencies

Generating entanglement between microwave photons and qubits in multiple cavities coupled by a superconducting qutrit

We discuss how to generate entangled coherent states of four \textrm{microwave} resonators \textrm{(a.k.a. cavities)} coupled by a superconducting qubit. We also show \textrm{that} a GHZ state of four superconducting qubits embedded in four different resonators \textrm{can be created with this scheme}. In principle, \textrm{the proposed method} can be extended to create an entangled coherent state of $n$ resonators and to prepare a Greenberger-Horne-Zeilinger (GHZ) state of $n$ qubits distributed over $n$ cavities in a quantum network. In addition, it is noted that four resonators coupled by a coupler qubit may be used as a basic circuit block to build a two-dimensional quantum network, which is useful for scalable quantum information processing.Comment: 13 pages, 7 figure

"Public Sector Pension Governance and Performance"

This paper investigates the determinants of public sector pension plan investment and funding behavior. Its goal is to draw lessons which may be used to improve the design and governance of public pensions. Plan performance is related to characteristics of the pension systems' governance structure and authority, using a new survey of U.S. state and local public pension plan governance practices and performance outcomes. The study suggests that most large public pension systems funded their plans satisfactorily in 1990, but some did not. Better public pension funding was associated with a pension system having in-house actuaries and when pension Board members were required to carry liability insurance. In contrast, public pension funding was lower when states experienced fiscal stress, and when employees were represented on the pension system Board. Pension funding did not appear sensitive to statutes guaranteeing benefits or funding levels, nor by the ability of states to carry budget deficits from one year to the next. The results also suggest that public pension Boards having more retiree-Trustees experienced lower investment returns, as did public sector pension plans required to devote a portion of their assets to in-state investments. Returns did not differ depending on whether a pension Board had in-house, or external money managers. No single set of pension plan management practices can optimize plan performance for all systems across all time periods. Nevertheless, these results suggest that care must be taken when designing the regulatory and investment environment in which these plans operate.

Credit and economic activity: shocks or propagation mechanism?

Credit