ABSTRACT
We study the nonreciprocal excitation and entanglement dynamics of two giant atoms (GAs) coupling to a one-dimensional waveguide. With different positions of coupling points, three configurations of two separate GAs, two braided GAs, and two nested GAs are analyzed, respectively. The coupling strengths between different coupling points are considered as complex numbers with phases. For each coupling configuration, the nonreciprocal excitation dynamics and entanglement properties, which results from the phase differences of coupling strength and the phase induced by photon propagation between the two coupling points, are studied both in Markovian and non-Markovian regimes. The analytical solutions for nonreciprocal entanglement degree are given in the Markovian regime. It shows that the steady entanglement can be reached and strongly depends on the phases. Different from the case of the Markovian regime, the entanglement degree shows oscillating behavior in the non-Markovian regime. This work may find applications in the generation and controlling of entanglement in quantum networks based on waveguide quantum electrodynamics.
ABSTRACT
The single photon scattering properties in a waveguide coupling to a giant atom with a three-level system are investigated theoretically. One of the transitions of the giant atom couples to the waveguide at two points while the other one is driven by a classical field. Using the analytical expressions of the single photon scattering amplitudes, the conditions for realizing perfect single photon nonreciprocal scattering are discussed in both Markovian regime and non-Markovian regime. In the Markovian regime, the perfect non-reciprocity can be realized by adjusting the external classical field, the energy dissipation of the giant atom, the phase difference between the two coupling strengths and the accumulated phase resulting from the photon propagating between the two coupling points. In the non-Markovian regime, the non-reciprocal scattering phenomenon becomes more abundant due to the time delay. However, the analytical results show that the perfect non-reciprocity can still be achieved. When the incident photon is resonant with the giant atom, the nonreciprocity can be switched by controlling the classical field. For the non-resonant single photon, one can adjust the Rabi frequency of the classical field to obtain the perfect non-reciprocal single photon transmission. Our work provides a manner to realize a frequency tunable single photon diode.
ABSTRACT
Transparent glass ceramics (GCs) containing Ba4Yb3F17:Er3+ nanocrystals were successfully fabricated by a traditional melt-quenching method. The formation of Ba4Yb3F17 nanocrystals was confirmed by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. Compared with the precursor glass, the enhanced emission intensity and lifetime of GCs indicate that the Er3+ ions incorporate into the Ba4Yb3F17 nanocrystals after crystallization. The color tuning properties with doping under 980 nm excitation have been systematically discussed. It was found that the red/green ratio increased with Er3+ ion doping and the corresponding color changed from greenish-yellow to yellow-green. Furthermore, the temperature-dependent luminescence properties were studied in detail by the fluorescence intensity ratio (FIR) technique. The monotonic change of FIR with temperature indicates that this material is suitable for temperature sensing. At a temperature of 450 K, the relative sensitivity of the prepared sample reached its maximal value of 0.20% K-1. The results show that the GCs containing Ba4Yb3F17:Er3+ nanocrystals are candidate materials for temperature sensing.
ABSTRACT
The two-mode entangled state is an important basic non-classical state and it has been used in many quantum communication projects. We propose a new quantum communication scheme with a two-mode entangled state which can transmit signals encoded by a thermal-state light field. Also, instead of locking several phases in the whole process, we use only one locking servo system at the final stage. The locking error signal comes from the measured quantum variances by using the quantum noise locking method. A proof-of-principle derivation shows that it is very convenient to achieve the secure condition against individual attacks. It would be utilized in practical quantum information process.
ABSTRACT
To suppress the internal electronic leakage at ceria-based electrolyte, a novel electron-blocking layer consisting of doped BaCe0.8Y0.2O3-δ was fabricated in situ at the interface of Ba-containing anode and Y-doped ceria electrolyte. The anode-supported full cell based on Y0.2Ce0.8O1.9 (YDC20) electrolyte presents a remarkable peak power density of 814 mW/cm2 as well as an open-circuit voltage of 1.0 V at 650 °C, which are much higher than those of the cells with Gd0.1Ce0.9O1.95 (GDC10) electrolyte (453 mW/cm2 at 650 °C) and BaCe0.8Y0.2O3-δ|Y0.2Ce0.8O1.9 (BCY|YDC20) bilayered electrolyte (419 mW/cm2 at 650 °C). The efficient promotion of the electron-blocking interlayer with high oxygen ionic conductivity is considered as the main reason for the improved performance of YDC20-based solid oxide fuel cell. The composition and the microstructure of the electron-blocking interlayer are further analyzed by scanning electron microscope and transmission electron microscope characterizations.
