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Elements of Quantum Electronics
Published in Michael Olorunfunmi Kolawole, Electronics, 2020
Like error correction being central to classical information theory, QEC is similarly foundational in quantum information theory. Both classical information theory and quantum information theory are concerned with the fundamental problem of error propagation in communication channel, as well as in information storage, in the presence of noise. Due to the uncertainty of its physical quantity, quantum noise appears as shot noise—quantum-limited intensity noise—caused by current fluctuations due to discreteness of the electrical charge. (Shot noise has been discussed in Chapter 6, Section 6.1.) Error-correction techniques are themselves susceptible to noise. For instance, when we perform multiple-qubit gates during a quantum computation, any existing errors in the system can propagate to other qubits, even if the gate itself is perfect. As such, we need to avoid, or at least limit or reduce error propagation in communication process.
Direct Modulation of Laser and Optical Injection Locking Sources
Published in Le Nguyen Binh, Optical Modulation, 2017
Minimization of laser noise can be done on entirely different routes: A first approach is the minimization of external noise influences, for example, by using single-frequency pump diodes operated with a carefully stabilized current source, and making a mechanical stable laser setup.A second possibility is the optimization of laser parameters such that the impact of quantum noise and/or external noise influences is minimized. For example, one may minimize quantum noise influences by using a long low-loss laser resonator, or move the relaxation oscillation frequency into a region where noise is less strongly disturbing the application.Finally, one may reduce laser noise with a feedback system, automatically adjusting, for example, the pump power based on measured output power fluctuations. The characteristics of the feedback loop need to be optimized based on the knowledge of laser parameters.
Nonlinear Dynamics in Quantum Photonic Structures
Published in Joachim Piprek, Handbook of Optoelectronic Device Modeling and Simulation, 2017
Gabriela Slavcheva, Mirella Koleva
One example of a quantum-optical phenomenon is quantum noise. In contrast to the more familiar classical noise, which can be regarded as spontaneous random fluctuations from a steady state, quantum noise arises from the Heisenberg uncertainty relations, which are fundamental to quantum theory [77]. The concept of quantum noise stems from the statistical interpretation of quantum mechanics and our inability to access any particular one out of the infinite number of degrees of freedom of the electromagnetic field propagating in free space. Quantum noise is closely related to spontaneous emission, irreversible decay and the origin of the spectral line width described by the theory of Weisskopf and Wigner [78], who are considered to have laid the foundations of the quantum noise theory.
Denoising for satellite laser altimetry full-waveform data based on EMD-Hurst analysis
Published in International Journal of Digital Earth, 2020
Zhijie Zhang, Huan Xie, Xiaohua Tong, Hanwei Zhang, Yang Liu, Binbin Li
From the perspective of noise sources in space-borne full-waveforms, they can be described as follows (Gardner 1992): (1) signal-caused quantum noise; (2) background noise from the sun, atmosphere, clouds, etc.; (3) detector noise (e.g. thermal noise, dark current noise); and (4) component noise (e.g. preamplifier noise). Among these noise sources, quantum noise, background noise, and dark current noise are common types of shot noise (belonging to white noise), whose possibility distribution functions obey Poisson distributions (Liu et al. 2006). Thermal noise is also referred to as white noise under the assumption of a Gaussian distribution (Bufton 1989). The combination of above noise types can still be regarded as white noise which obeys a Gaussian distribution.
Nonclassical properties of a deformed atom-cavity field state
Published in Journal of Modern Optics, 2022
Naveen Kumar, Arpita Chatterjee
The conventional Jaynes–Cummings model (JCM) [1] describes the atom-cavity interaction as a two-level atom is colliding with a single mode of the electromagnetic field in the matter–radiation coupling. This model is proposed as a basic design to investigate the semiclassical behaviour of quantum radiation field [2]. The generalized Jaynes–Cummings model, illustrating the nonlinear interaction of a two or multi-level atom with a cavity field, results a deformed JCM structure. In quantum optics and quantum information processing [3], the nonclassical light field is of major interest for a number of reasons. In an all-optical quantum information processing device [4], the single-photon Fock state, a nonclassical state, is an essential resource. Controlling the emission of a single radiator, such as a molecule or a quanta [5], can be used to create these states. Fock state can also be prepared using cavity QED experiments in which atoms interact one at a time with a high Q resonator. A π quantum Rabi pulse in a microwave cavity [6] or an adiabatic passage sequence in an optical cavity [7] can produce a one-photon Fock state in this way. The study of these states yields a fundamental understanding of quantum fluctuations and a new method of quantum communication or imaging that surpasses the standard quantum noise limit. Nonclassical states have a wide range of real-world applications. For example, squeezed states are used to reduce the noise level in one of the phase-space quadratures below the quantum limit [8], entangled states are employed to realize a quantum computer and to transfer quantum information [9]. Here under the rotating-wave approximation (RWA), we investigate the dynamics of two-photon correlations generated by the interaction of a semiclassical two-level atom with a single-mode cavity field.
Low-dose CT image denoising using sparse 3d transformation with probabilistic non-local means for clinical applications
Published in The Imaging Science Journal, 2023
Dawa Chyophel Lepcha, Bhawna Goyal, Ayush Dogra
Computed tomography has a high contrast sensitivity characteristic which is used to differentiate among the soft tissues within the human body. This characteristic is affected by noise which harms the visualization of low-contrast structure [3]. It may arise from the detection of a finite number of X-ray quanta in the projection. It looks like a fluctuation in the image density. As a result, the change into image density is unpredictable and in random manner, this is known as random noise. The energy of X-rays is transmitted in the form of individual chunks of energy called quanta. Therefore, these finite number of X-ray quanta are detected by the X-ray detector. The number of detected X-ray quanta may differ with another measurement because of statistical fluctuation. The statistical noise in CT images may appear because of fluctuations in detecting a finite number of X-ray quanta. Statistical noise may also be called quantum noise. There are electric circuits to receive analogue signals which are also known as analogue circuits. The process of receiving analogue signals by the electronic circuits may be affected with some noise, which is referred as electronic noise. The analogue signals are converted into digital signals using signal-processing steps and then sent to the digital computer for CT image reconstruction. In digital computers, there are digital circuits to handle the process of discrete signals. Due to limited number of bits for storage of discrete signals in computer system, mathematical computation is not possible without roundoff. This limitation is referred as roundoff errors. A continuously varying error due to electrical noise or roundoff errors, can be modelled as a simple additive noise, and second reason is the possible error due to random variations in detected X-ray intensity. CT images are prone to Gaussian noise due to the electrical signals. The high-speed computation of CT images from multiple planar views results in thermal energy fluctuations which lead to the manifestation of Gaussian noise in these images. Besides this CT images are also noisy due to mathematical computations and quantum statistics.