arXiv subjects

Claes G. Granqvist

Publications and source records attributed to Claes G. Granqvist.

7 recordsLinked to original sources

arXiv2015

Zero-point term and quantum effects in the Johnson noise of resistors: A critical appraisal

There is a longstanding debate about the zero-point term in the Johnson noise voltage of a resistor. This term originates from a quantum-theoretical treatment of the Fluctuation-Dissipation Theorem (FDT). Is the zero-point term really there, or is it only an experimental artefact, due to the uncertainty principle, for phase-sensitive amplifiers? Could it be removed by renormalization of theories? We discuss some historical measurement schemes that do not lead to the effect predicted by the FDT, and we analyse new features that emerge when the consequences of the zero-point term are measured via the mean energy and force in a capacitor shunting the resistor. If these measurements verify the existence of a zero-point term in the noise, then two types of perpetual motion machines can be constructed. Further investigation with the same approach shows that, in the quantum limit, the Johnson-Nyquist formula is also invalid under general conditions even though it is valid for a resistor-antenna system. Therefore we conclude that and a satisfactory quantum theory of the Johnson noise, the Fluctuation-Dissipation Theorem, must, as a minimum, include also the measurement system used to evaluate the observed quantities. Issues concerning the zero-point term may also have implications for phenomena in advanced nanotechnology.

physics.gen-ph↗

arXiv2015

Zero and negative energy dissipation at information-theoretic erasure

We introduce information-theoretic erasure based on Shannon's binary channel formula. It is pointed out that this type of erasure is a natural energy-dissipation-free way in which information is lost in double-potential-well memories, and it may be the reason why the brain can forget things effortlessly. We also demonstrate a new non-volatile, charge-based memory scheme wherein the erasure can be associated with even negative energy dissipation; this implies that the memory's environment is cooled during information erasure and contradicts Landauer's principle of erasure dissipation. On the other hand, writing new information into the memory always requires positive energy dissipation in our schemes. Finally, we show a simple system where even a classical erasure process yields negative energy dissipation of arbitrarily large energy.

cs.ET↗

arXiv2014

Current and voltage based bit errors and their combined mitigation for the Kirchhoff-law-Johnson-noise secure key exchange

We classify and analyze bit errors in the current measurement mode of the Kirchhoff-law-Johnson-noise (KLJN) key distribution. The error probability decays exponentially with increasing bit exchange period and fixed bandwidth, which is similar to the error probability decay in the voltage measurement mode. We also analyze the combination of voltage and current modes for error removal. In this combination method, the error probability is still an exponential function that decays with the duration of the bit exchange period, but it has superior fidelity to the former schemes.

cs.CR↗

arXiv2012

Energy Requirement of Control: Comments on Szilard's Engine and Maxwell's Demon

In mathematical physical analyses of Szilard's engine and Maxwell's demon, a general assumption (explicit or implicit) is that one can neglect the energy needed for relocating the piston in Szilard's engine and for driving the trap door in Maxwell's demon. If this basic assumption is wrong, then the conclusions of a vast literature on the implications of the Second Law of Thermodynamics and of Landauer's erasure theorem are incorrect too. Our analyses of the fundamental information physical aspects of various type of control within Szilard's engine and Maxwell's demon indicate that the entropy production due to the necessary generation of information yield much greater energy dissipation than the energy Szilard's engine is able to produce even if all sources of dissipation in the rest of these demons (due to measurement, decision, memory, etc) are neglected.

physics.gen-ph↗

arXiv2012

Optimum Drift Velocity for Single Molecule Fluorescence Bursts in Micro/Nano-Fluidic Channels

Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic channels provided the width of the histogram is narrow. Photonic shot noise and residence time fluctuations, caused by longitudinal diffusion, are the major sources of the histogram width. This Communication is a sequel to an earlier Letter of ours [L. L. Kish et al., Appl. Phys. Lett. 99, 143121 (2011)] and demonstrates that, for a given diffusion coefficient, an increase of the drift velocity enhances the relative shot noise and decreases the relative residence time fluctuations. This leads to an optimum drift velocity which minimizes the histogram width and maximizes the ability to identify single molecules, which is an important result for applications.

physics.gen-ph↗

arXiv2011

Log-Normal Distribution of Single Molecule Fluorescence Bursts in Micro/Nano-Fluidic Channels

The width and shape of photon burst histograms pose significant limitations to the identification of single molecules in micro/nano-fluidic channels, and the nature of these histograms is not fully understood. To reach a deeper understanding, we performed computer simulations based on a Gaussian beam intensity profile with various fluidic channel diameters and assuming (i) a deterministic (noise-free) case, (ii) photon emission/absorption noise, and (iii) photon noise with diffusion. Photon noise in narrow channels yields a Gaussian burst distribution while additional strong diffusion produces skewed histograms. We use the fluctuating residence time picture [Phys. Rev. Lett. 80, 2386-2388 (1998)] and conclude that the skewness of the photon number distribution is caused by the longitudinal diffusive component of the motion of the molecules as they traverse the laser beam. In the case of strong diffusion in narrow channels, this effect leads to a log-normal distribution. We show that the same effect can transform the separate peaks of the photon burst histograms of multiple molecule mixtures into a single log-normal shape.

physics.data-an↗

arXiv2010

Fluctuation-Enhanced Sensing for Biological Agent Detection and Identification

We survey and show our earlier results about three different ways of fluctuation-enhanced sensing of bio agent, the phage-based method for bacterium detection published earlier; sensing and evaluating the odors of microbes; and spectral and amplitude distribution analysis of noise in light scattering to identify spores based on their diffusion coefficient.

physics.bio-ph↗