Driving-dependent damping of Rabi oscillations in two-level semiconductor systems

We propose a mechanism to explain the nature of the damping of Rabi oscillations with increasing driving-pulse area in localized semiconductor systems, and have suggested a general approach which describes a coherently driven two-level system interacting with a dephasing reservoir. Present calculations show that the non-Markovian character of the reservoir leads to the dependence of the dephasing rate on the driving-field intensity, as observed experimentally. Moreover, we have shown that the damping of Rabi oscillations might occur as a result of different dephasing mechanisms for both stationary and non-stationary effects due to coupling to the environment. Present calculated results are found in quite good agreement with available experimental measurements

Measuring photon-photon interactions via photon detection

The strong non-linearity plays a significant role in physics, particularly, in designing novel quantum sources of light and matter as well as in quantum chemistry or quantum biology. In simple systems, the photon-photon interaction can be determined analytically. However, it becomes challenging to obtain it for more compex systems. Therefore, we show here how to measure strong non-linearities via allowing the sample to interact with a weakly pumped quantized leaking optical mode. We found that the detected mean-photon number versus pump-field frequency shows several peaks. Interestingly, the interval between neighbour peaks equals the photon-photon interaction potential. Furthermore, the system exhibits sub-Poissonian photon statistics, entanglement and photon switching with less than one photon. Finally, we connect our study with existing related experiments.Comment: 4 pages, 3 figure

Single-atom laser generates nonlinear coherent states

The stationary state of a single-atom (single-qubit) laser is shown to be a phase-averaged nonlinear coherent state - an eigenstate of a specific deformed annihilation operator. The solution found for the stationary state is unique and valid for all regimes of the single-qubit laser operation. We have found the parametrization of the deformed annihilation operator which provides superconvergence in finding the stationary state by iteration. It is also shown that, contrary to the case of the usual laser with constant Einstein coefficients describing transition probabilities, for the single-atom laser the interaction-induced transition probabilities effectively depend on the field intensity

Spin Properties of Germanium-Vacancy Centers in Bulk and Near-Surface Regions of Diamond

Germanium-vacancy (GeV) centers are now studied extensively due to perspectives of their applications in quantum information processing, nanometrology and nanoscale magnetic resonance imaging. One of the important requirements for these applications is a detailed understanding of the hyperfine interactions in such systems. Quantum chemistry simulation of the negatively charged GeV− color center in diamond is the primary goal of this paper in which we present preliminary results of computer simulation of the bulk H-terminated cluster C6969[GeV−]H8484, as well as of the surface cluster C6464[GeV−]H6868_(100)_H1111 having one dangling bond at (1 0 0) surface using the DFT/PW91/RI/def2-SVP level of theory

Asymmetric universal entangling machine

We give a definition of asymmetric universal entangling machine which entangles a system in an unknown state to a specially prepared ancilla. The machine produces a fixed state-independent amount of entanglement in exchange to a fixed degradation of the system state fidelity. We describe explicitly such a machine for any quantum system having $d$ levels and prove its optimality. We show that a $d^2$-dimensional ancilla is sufficient for reaching optimality. The introduced machine is a generalization to a number of widely investigated universal quantum devices such as the symmetric and asymmetric quantum cloners, the symmetric quantum entangler, the quantum information distributor and the universal-NOT gate.Comment: 28 pages, 3 figure

МЕЖДУНАРОДНЫЙ ГОД СВЕТА И ОПТИЧЕСКИХ ТЕХНОЛОГИЙ

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