FLUCTUATION AND NOISE EXPLOITATION LABORATORY
Dept. of Electrical and Computer Engineering, Texas A&M University
in Physics and Information Technology
What we show in this page below is similar in nature to the Discovery Channel's MythBusters (see on the left) who bust or verify everyday myths, except that we do this within the professional fields of science and technology. As a consequence, while our story can sometimes be as funny as their show; the stakes and the matters are much more serious with potential impacts on the direction of science/technology and its funding. The sad part of the story is that there is a flood of new myths in science, in the popular science media and even in some of the leading scientific journals. The myths usually come with a great hype that can potentially discredit reasonable scientific claims, if the present trend continues.
Below, a few of the important myths that we had busted are shown, in (roughly) inverse-chronological-order. We focus on myths where stochastics has a role (explicit or implicit).
1. Information entropy and thermodynamic entropy: apples and oranges
It had generally been assumed that there is a
general interrelation between the information entropy and the
thermodynamical entropy in physical systems.
Status of myth:
More details: We have shown that the two major efforts to find general physical principles that interrelate changes in the information entropy and the thermal entropy in physical systems are invalid.
i) In general, the information entropy and its changes contain a component that is subjective to the measurement instrument, while the changes of thermal entropy can be stated objectively.
ii) Brillouin's negentropy principle of information (the expanded formulation of the Second Law), is invalid as a general rule because violations can also occur in a physical system provided the temperature of the measurement system is lower than that of the measured physical system.
iii) In the case of homogeneous temperatures, it can be seemingly valid if the measurement system is integrated with the measured physical system, or if not, it can be valid within the measurement system alone. However, in classical physical situations, the measurement system and the measured physical system, as well as the change of information entropy and the related change of thermal entropy can be separated in space and time leading to the break of Brillouin's negentropy principle.
iv) The information entropy can increase without triggering any change of the thermal entropy indicating that information erasure does not necessarily require energy dissipation.
v) There is no case where Landauer's principle of erasure dissipation is even seemingly valid because erasing of the known memory content by resetting does not yield change in the information entropy.
vi) The information entropy can violate the Third Law of Thermodynamics.
Paper: L.B. Kish, D. Ferry, "Information entropy and thermal entropy: apples and oranges", accepted for publication in Journal of Computational Electronics (2017). download
See also https://arxiv.org/abs/1706.01459 .
2. Memristors are not the "missing" circuit elements because they are not necessarily passive
Myth: It has been claimed that the memristor is the "missing" (passive) circuit element.
Status of myth:
Chua's general proof that the memristor is passive based on his memristor equations is invalid because the memristor equations do not provide a sufficient description of the physics of memristors. A relevant statistical thermodynamics is needed for the memristors however the memristor equations do not contain sufficient physics to deduce that.
While the response functions of passive resistors, capacitors and inductors determine their Fluctuation-Dissipation Theorem (FDT), the memristor model lacks sufficient physics for a FDT. To create the noise theory (FDT) of a memristor, it is essential to know the internal material structure of the particular memristor thus its generic formulation, like it is done with the three basic circuit elements, is impossible.
- K. Sundqvist, D.K. Ferry, L.B. Kish, "Memristor equations: incomplete physics and undefined passivity/activity", Fluctuation and Noise Lett. 16 (2017) 1771001. download
See also: https://arxiv.org/abs/1703.09064
- K.M. Sundqvist, D.K. Ferry, L.B. Kish, "Second Law based definition of passivity/activity of devices", Physics Letters A 381 (2017) 3364–3368. download
See also: https://arxiv.org/abs/1705.08750
3. Non-zero thermal noise at zero temperature due to the quantum Fluctuation-Dissipation-Theorem
Myth: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). The classical Johnson–Nyquist formula vanishes at the approach of zero temperature, but the quantum zero-point term still predicts non-zero noise voltage and current. The myth is that such a zeropoint noise is objectively present in the system independently from the type of measurement equipment.
Status of myth: Busted.
Reason: New features 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 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.
Moreover, we showed that thezero-point noise cannot be reconciled with the Fermi–Dirac distribution, which defines the thermodynamics of electrons according to quantum-statistical physics. Consequently, Johnson noise must be nil at zero temperature, and non-zero noise found for certain experimental arrangements may be an measurement artifact, such as the one mentioned in Kleen’s uncertainty relation argument.
- L.B. Kish, G.A. Niklasson, C.G Granqvist, "Zero-point term and quantum effects in the Johnson noise of resistors: A critical appraisal", J. Statistical Mechanics 2016 (2016) 054006. doi:10.1088/1742-5468/2016/05/054006 . See also: http://arxiv.org/abs/1504.08229 .
- L.B. Kish, G.A. Niklasson, C.G. Granqvist, "Zero thermal noise in resistors at zero temperature", Fluctuation and Noise Lett. 15 (2016) 1640001.
4. Unconditionally secure communications (key exchange) provided by the laws of physics (2005-present)
It had generally been assumed that only quantum
physics was able to provide unconditional
security of the key exchange. Securing a
classical wire without a previously exchanged
secret key seemed to be impossible because the
current and voltage are measurable without
disturbing the system (at least in the ideal