Fisher information of a single qubit interacts with a spin-qubit in the presence of a magnetic field

In this contribution, quantum Fisher information is utilized to estimate the parameters of a central qubit interacting with a single-spin qubit. The effect of the longitudinal, transverse and the rotating strengths of the magnetic field on the estimation degree is discussed. It is shown that, in the resonance case, the number of peaks and consequently the size of the estimation regions increase as the rotating magnetic field strength increases. The precision estimation of the central qubit parameters depends on the initial state settings of the central and the spin- qubit, either encode classical or quantum information. It is displayed that, the upper bounds of the estimation degree are large if the two qubits encode classical information. In the non-resonance case, the estimation degree depends on which of the longitudinal/transverse strength is larger. The coupling constant between the central qubit and the spin- qubit has a different effect on the estimation degree of the weight and the phase parameters, where the possibility of estimating the weight parameter decreases as the coupling constant increases, while it increases for the phase parameter. For large number of spin-particles, namely, we have a spin-bath particles, the upper bounds of the Fisher information with respect to the weight parameter of the central qubit decreases as the number of the spin particle increases. As the interaction time increases, the upper bounds appear at different initial values of the weight parameter

Economic benefits of supersonic overland operation

Environmental concerns are likely to impose some restrictions on the next generation of supersonic commercial transport. There is a global concern over the effects of engine emissions on the ozone layer which protects life on Earth from ultraviolet radiation. There is also some concern over community noise. The High Speed Civil Transport (HSCT) must meet at least the current subsonic noise certification standards to be compatible with the future subsonic fleet. Concerns over sonic boom represent another environmental and marketing challenge to the HSCT program. The most attractive feature of the supersonic transport is speed, which offers the traveling public significant time-savings on long range routes. The sonic boom issue represents a major environmental and economic challenge as well. Supersonic operation overland produces the most desirable economic results. However, unacceptable overland sonic boom raise levels may force HSCT to use subsonic speeds overland. These environmental and economic challenges are likely to impose some restrictions on supersonic operation, thus introducing major changes to existing route structures and future supersonic network composition. The current subsonic route structure may have to be altered for supersonic transports to avoid sensitive areas in the stratosphere or to minimize overland flight tracks. It is important to examine the alternative route structure and the impact of these restrictions on the economic viability of the overall supersonic operation. Future market potential for HSCT fleets must be large enough to enable engine and airframe manufacturers to build the plane at a cost that provides them with an attractive return on investment and to sell it at a price that allows the airlines to operate with a reasonable margin of profit. Subsonic overland operation of a supersonic aircraft hinders its economic viability. Ways to increase the market potential of supersonic operation are described

Dynamics of encrypted information in the presence of imperfect operations

The original dense coding protocol is achieved via quantum channel generated between a single Cooper pair and a cavity. The dynamics of the coded and decoded information are investigated for different values of the channel's parameters. The efficiency of this channel for coding and decoding information depends on the initial state settings of the Cooper pair. It is shown that, these information increase as the detuning parameter increases or the number of photons inside the cavity decreases. The coded and decoded information increase as the ratio of the capacities between the box and gate decreases. In the presence of imperfect operation, the sensitivity of the information to the phase error is much larger than the bit flip error

Estimation of pulsed driven qubit parameters via quantum Fisher information

We estimate the initial weight and phase parameters ($\theta, \phi)$ of a single qubit system initially prepared in the coherent state $\ket{\theta,\phi}$ and interacts with three different shape of pulses; rectangular, exponential, and $sin^2$-pulses. In general, we show that the estimation degree of the weight parameter depends on the pulse shape and the initial phase angle, $(\phi)$. For the rectangular pulse case, increasing the estimating rate of the weight parameter via the Fisher information function $(\mathcal{F}_\theta)$ is possible with small values of the atomic detuning parameter and larger values of the pulse strength. Fisher information $(\mathcal{F}_\phi)$ increases suddenly at resonant case to reach its maximum value if the initial phase $\phi=\pi/2$ and consequently one may estimate the phase parameter with high degree of precision. If the initial system is coded with classical information, the upper bounds of Fisher information for resonant and non-resonant cases are much larger and consequently one may estimate the pahse parameter with high degree of estimation. Similarly as the detuning increases the Fisher information decreases and therefore the possibility of estimating the phase parameter decreases. For exponential, and $sin^2$-pulses the Fisher information is maximum ($\mathcal{F}_{\theta,\phi}=1$) and consequently one can always estimate the weight and the phase parameters $(\theta,\phi)$ with high degree of precision