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Piezoelectric sensors used for the detection of chemical agents and as electronic nose instruments are based on bulk and surface acoustic wave resonators. Adsorption of gas molecules on the surface of the polymer coating is detected by a reduction of the resonance frequency of the quartz disk, subject also to fundamental quantum 1/f frequency fluctuations.The quantum 1/f limit of detection is given by the quantum 1/f formula for quartz resonators. Therefore, for quantum 1/f optimization and for calculation and improvement of the fundamental sensitivity limits, we must avoid closeness of the crystal size to the phonon coherence length, which corresponds to the maximum error and minimal sensitivity situation, as shown here. Adsorbed masses below the pg range can be detected.Microelectromechanical system (MEMS) resonators have provided a possibility for the nanominiaturization of these sensors. Essential for integrated nanotechnology, these resonant silicon bars (fingers) are excited magnetically or electrically through external applied forces, since they are not piezoelectric or magnetostrictive. The application of the quantum 1/f theory to these systems is published here for the first time. It provides simple formulas that yield much lower quantum 1/f frequency fluctuations for magnetic excitation, in comparison with electrostatically driven MEMS resonators.

For imaging and remote sensing applications, the noise of the THz detector must be minimized. The quantum 1/f theory is introduced and used to obtain analytical expressions of noise in n + p diodes, Schottky diode THz detectors and mixers, a new type of suggested MEMS resonator based Thz detectors, QWIPs and bolometers. For the DAR and for THz communications we also consider phase noise in RTD and GaN/AlGaN HFET based THz generators.

Spintronics is a new direction in electronics. It contains many applications, including spin valves, GMR devices, "spin batteries," spin-controlled electronic devices, and even spin -controlled wide-bandgap compound semiconductors due to the development of rare-earth-doped nitrides with ferromagnetic properties. Spintronics allows for manipulation of both the spin transport and the charge transported by the electrons. It allows the downscaling to lower device sizes and extension of Moore's law to higher device densities, because it requires less energy to just control the spin of the electron, and the quantum 1/f noise associated with spin control is several orders of magnitude below that associated with conventional electronics. However, the injected spin-polarized current is subject to spin-flip due to various causes. The rate of each of these spin-flip currents is affected by quantum 1/f noise, because of the low-frequency photon emission amplitude that is associated with the elementary spin flip process, no matter what causes the spin flip. As a result, in a spin valve, the leakage current will show 1/f noise. In devices with injection and subsequent control of spin-polarized electrons, the effects obtained will also show this spintronic quantum 1/f noise. For instance, the light output of a spin-controlled LED will exhibit quantum 1/f intensity fluctuations. The present paper calculates the 1/f noise expected in spintronic currents. The spectral density of this fundamental 1/f noise is inherently proportional to the square of the current that is affected by it, but is also inversely proportional to the number of carriers defining this current. The latter dependence can cause the spectrum to be proportional to the first power of the current.

Quantum 1/f noise is the manifestation of the coherent and conventional quantum 1/f effects (Q1/fE). The conventional Q1/fE is a fundamental quantum fluctuation of physical cross sections σ and process rates Γ, caused by the bremsstrahlung (recoil) energy and momentum losses of charged particles, when they are scattered, or accelerated in any way. The closely related coherent Q1/fE is present in any current carried by many particles. It is caused by the energy spread characterizing any coherent state of the electromagnetic field oscillators. According to the Heisenberg's uncertainty principle, because an approximation of the phase or position variable is known, exact knowledge of the energy is precluded. This energy spread results in nonstationary energy values, or fluctuations in the energy of the oscillators. To find the spectral density of these inescapable basic fluctuations, which are known to characterize any quantum state, which is not an energy eigenstate, we use an elementary physical derivation based on Schrödinger's definition of coherent states, which can be supplemented by a rigorous derivation from a well-known quantum-electrodynamical branch-point propagator. The example of a simple harmonic oscillator is also useful for illustrating the uncertainty that arises due to Q 1/f Noise. Clearly illustrating the relation between the uncertainty principle and Q 1/f noise.