China
Africa
Explore chapters and articles related to this topic
The Basics of Lasers
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
In a slightly different picture of polarization direction, one can envisage a particular direction as a superposition of waves of different amplitude oscillating in the, say, x- and y-directions. For equal amplitudes, therefore, the resultant superposition would oscillate in a direction at 45° to the x- and y-axes. If, in addition, if said two waves of equal amplitude experience a phase shift of ±π/2, the phenomenon of circular polarization is encountered. During wave propagation, the superposition of the two E-fields results in a total E-vector, which rotates clockwise/anticlockwise at the angular wave frequency ω. The former case is known as σ+ polarization, while the latter one is associated with σ− polarization. Frequently, the linear-polarization case is said to be a superposition of two σ+/σ− polarization waves, which yield the so-called π polarization. Linear and circular polarized waves can be transformed between each other by using a quarter-wave plate (or λ/4-plate). Sending a linear polarized wave through a quarter-wave plate, whose e- and o-axes are adjusted at 45° to each other, results in a circular polarized wave, and vice versa (see Figure 3.26). The σ+/σ− polarization states can be thought of as related to photon polarization states. When the light intensity is reduced to its smallest possible level, one deals with single photons, i.e., quantized light. At the photon level, the “polarization” is related to its intrinsic angular momentum (spin), sphoton = ±h. This means that on photon absorption/emission in an interaction experiment, not only energy conservation but also angular momentum conservation have to be considered.
Review of Security Methods Based on Classical Cryptography and Quantum Cryptography
Published in Cybernetics and Systems, 2023
Shalini Subramani, Selvi M, Kannan A, Santhosh Kumar Svn
During the transmission between Gracie and Jack, Eve is quietly listening to the quantum channel communication and Eve cannot encrypt or decrypt their keys. When the secret-key distillation techniques are used to recover the errors from their quantum bits and it distills key, then forms a secret key for Gracie and Jack that are unknown for Eavesdropper (Eve). Perhaps most Quantum Key Distribution techniques use these techniques if their channels have right-handed circular polarization and left-handed and they are used to measure their quantum through phase state (Laszlo Gyongyosi, et al., 2019). They allow beam splitter to measure photon polarization in vertical and horizontal states. The beam splitter is an optical component to split incident light at a destination ratio into two separate beams and they reverse it to join two different variations of beams into a single one phase. Now, the two modes of beam splitter are “in” modes and “out” modes using equation (5).
Band structures and optical properties related to substitutional impurities in TlGaSe2 layered crystals: first-principles study
Published in Phase Transitions, 2019
L. Yu Kharkhalis, K. E. Glukhov, T. Ya Babuka, M. V. Liakh
At zero energy Е= 0 refractive indices for pure TlGaSe2 are following: nx= ny= 2.99, and nz= 3.1 (nexp∼2.6–2.8 [9,11]). High peaks for the refractive indices (nx,y∼3.67, and nz∼3.72) are observed at the energy E∼2.54 eV for E || a1(a2) and Е∼2.56 еV for E || a3 that corresponds to the visible spectral region. The maximum value of ε1x(ω) was found to be 13.0 at E ∼ 2.33 eV and ε1z(ω) ∼ 13.43 at E = 2.27 eV, which well correlates with the experiment [9]. The static dielectric constants (at E = 0) are equal to ε1x(0) ∼ 8.94 for the photon polarization E || a1(a2) and to ε1z(0) ∼ 9.5 for E || a3. As it is shown in Figure 5, a very slight anisotropy (nz(0)/nx(0)∼1.04) was found for these optical parameters. A similar anisotropy is observed for the real part of the dielectric function (ε1z(0)/ε1x(0) ∼1.06).
Rome teleportation experiment analysed in the Wigner representation: the role of the zeropoint fluctuations in complete one-photon polarization-momentum Bell-state analysis
Published in Journal of Modern Optics, 2018
A. Casado, S. Guerra, J. Plácido
In contrast, in the Rome teleportation experiment only two entangled photons are used, and the qubit to be teleported is encoded in one of two degrees of freedom (polarization or momentum) of Alice's photon (15). The other photon of the down-converted pair is sent to Bob. The advantage of this teleportation scheme is that a complete BSM of the four one-photon polarization-momentum Bell states is possible. Nevertheless, the input state cannot be supplied by an external system, and this presents some limitations, such as the inability to teleport entangled or mixed states (2). This experiment was proposed by Popescu (20) and performed in Rome by using two-photon momentum entanglement, and polarization coding for preparing the qubit to be teleported (15).