Quantum Tunnel of Love
By: Bob Sireno

Burn-in: The time during the early period of use when a component or cable exhibits measurable changes in performance, that eventually stabilize, resulting in consistent performance for a significant period of time thereafter. Things happen to be more complex than this simple definition of burn-in might lead one to believe. To gain a fuller understanding we must ask: what transpires inside of a circuit that causes it to stabilize? Why, after a period of time, is a device no longer subject to “drift”?  This paper proposes answers to these questions. But first, let me put forth my position on hi-end audio before the technical stuff begins.
I am a scientist, by trade, and therefore an objectivist. Twenty two years of experience on the job has taught me that all phenomena is measurable, but, not all phenomena can presently be measured. The technology of the measuring tool is not always adequate to measure empirical reality. People tend to accept this proposition in all areas other than audio.
I am also an audiophile. I hear differences in equipment, and in cables. I hear sonic changes that take place over time. I believe that audiophiles have better aural perception (not the same as hearing!) than the bulk of humanity, and that adequate test equipment needed to verify the subtleties they claim to hear in some cases, does not yet exist. Today we’ll look into the atomic world, where the explanations may exist for the sonic changes that seem to occur in our equipment and cables with the passage of time.

Atoms and molecules have recently been filmed in motion. PBS broadcast one of the first “;atomic movies”; several years ago. The show was called STEM. I was stunned. Up close, electrons literally look like thinly connected beads of gas. The depth of micro-reality made visible with a Scanning Tunneling Electron Microscope is incredible. The behavior of individual atoms was chaotic. Some appeared lethargic; temporarily bonding to others, while some were constantly moving. All of the atoms eventually paired off, vibrated, and moved on to pair off again, sometimes in groups of three or more.

What happens to the seemingly content atoms in a conductor when electrical pressure is applied? What happens when electron waves are driven through the circuitry of a new amp, CD player, cable, etc., (going through what we call its burn-in period) that causes some people to claim that nothing occurs because it can’t be measured, or to cause others to claim that a sweeter sound, or at least a different sound, is born over time and use?

Cables are made of metal crystals, typically copper or silver, containing spherically symmetrical positive ions, through which electrons move. The purest metal also contains one ten-thousandth of a percent, or so, of impurities. Each electron passing through a cable makes a series of left and right turns around those atomic impurities until it emerges.(1) What happens during this journey, multiplied by trillions, changes the nature of the cable sufficiently to affect the sound you hear over a period of time.
Metal crystals contain grain boundaries. A grain boundary is where two crystals meet, oriented so that their atoms are usually aligned in different directions. Researchers at Cornell University developed an x-ray technique that allowed them to probe the internal structure of grain interfaces. The results showed that atoms at grain boundaries appeared to vibrate 50 percent more energetically than non-boundary atoms.(2) Electrons tend toward lower energy levels, so when electrical pressure is applied, the increased energy brings about a slow reorientation of the atoms at the grain boundaries.  Afterwards, any reoriented atoms would vibrate less energetically. The outcome of the reorientation of atoms is less electron scattering resulting in improved electrical wave phase coherence.(3)
Dr. Robert Frank of Augustana College told me that “ion mobility leads to the migration of atoms over time...and to the movement of oxygen, carbon, hydrogen gas and hydrocarbon impurities” He stated that ion movement in copper wiring would probably occur over several months, creating a change in the filter nature, and a subtle change in the capacitance of the metal. To the extent that all cabling can be described mathematically as a filter device, a change in this aspect could cause a sonic deviation over time.

I believe the ion transfer Dr. Frank described, along with grain boundary reorientation, results in lower electron orbital levels in many of the boundary area atoms. These changes, induced over a period of time, may very well be the type of changes that are responsible, in part, for the burn-in effects that some audiophiles claim to hear.

While researching the concept of burn-in, I discovered a book entitled “Quantum Aspects Of Molecular Motions In Solids”. This fascinating, but highly pedantic book, focuses on the various aspects of quantum tunneling In the book there is a paper that describes the influence electrons have on the quantum tunneling of hydrogen atoms in a metal. The same paper also discusses rotational tunneling of methane, a simple hydrocarbon, in metal.(4) In other words, at least two of the common impurities found in electrical conductors, move slowly, by quantum tunneling, when electrical pressure is applied. The result, once again, is less electron scattering and a physical change in the conductor itself at a molecular level.

Quantum tunneling is a surprisingly common event. It occurs in every electrical connection, where a thin oxide layer has formed over a metal conductor. As long as the oxide layer remains thin, electrons can, and will, tunnel through the layer.(5) I propose that electrons will not always detour around impurities in a wire, but will tunnel their way through impurities that are small enough to allow the activity to occur. In either case pathways of conductivity are established during days, weeks, and months of use through the actual conductor themselves. Like the water reeling down a babbling brook, the electrons go around, or eventually thorough, boulders of impurity, always choosing the route of least resistance.
It appears that your new components, or cables, do indeed improve up to a point when the system they are in is left on for extended periods of time Obviously, there is a point at which no more perceptible change occurs. Why is that? Well, unfortunately electrons will continue to scatter around the remaining impurities, even after burn-in. Can circuits be designed that will not exhibit electron scattering, or burn-in? Yes, it is possible to design a circuit that is so small that the signal paths are the thickness of a single electron wavelength. The result is called a quantum wire. Efforts to make a practical quantum wire have so far failed. But, once again, theory is fast becoming reality.

AT&T’s Bell labs is working on a resistor that allows but a single electron through at a time.(6) Researchers at the University of California at Santa Barbara have assembled quantum wires one electron at a time.(7) Japanese scientists at the Optoelectronics Technology Research Laboratory, near Tokyo, believe that before quantum wires can be easily fabricated a deeper understanding of what happens on an atomic level during epitaxial (crystal) growth is needed, and are working toward that goal.( 8 ) An American company, Texas Instruments, has developed a tiny device called the BiQuaRTT, or bipolar quantum resonant tunneling transistor. At only two specific voltages, electrons tunnel through the circuit barriers causing current flow. Integrated circuits will be next. Someday quantum wire production will be perfected, along with the necessary IC’s, and we’ll have an entirely new generation of amplifiers, preamps and such.

When quantum wires become commercial and are fully utilized, perhaps in 20 to 25 years, the reproduced signal approaching the final amplification stages will be as perfect as possible, and cable burn-in will no longer be a subject of dispute. To fully utilize quantum wires, and minimize electron scattering, the final amplification stage may need to be located at, or in, the speaker. One can only hope that improved recording techniques will match the hardware development that will inevitably occur.

Scientifically, there is no doubt that the propagation of electrons through a conductor changes with time and use. These changes are minute, and measurable with only the most advanced of devices. But, they exist. And to exist means that claims concerning audibility must be taken seriously. Only a few years ago, audiophiles complained that circuits employing negative feedback affected the sound of amplifiers adversely. The number crunchers denied it because the distortion figures were so much improved with the use of feedback. Turns out the audiophiles were right... that may be the case again.

1-7-2012 addendum: Researchers led by Michelle Simmons of the Center for Quantum Computation and Communication Technology at the School of Physics of the University of New South Wales in Sydney have achieved quantum wires of 1.5-nm that do not exhibit high resistance.  Reference: http://www.sciencemag.org/content/335/6064/64

FOOTNOTES:
1)   Martin C. Guitzwiller, “Quantum Chaos” Scientific American, January 1992, p. 83.
2)   Science News, November 26, 1988, p. 348.
3)   F. Capasso, “Evolution of Quantum Semi-conductor Devices” Physics of Quantum Electron Devices, ed. Austin, Engl, Sugano, (Berlin 1990).
4)   A. Huller and L. Baetz, “The Temperature Dependence Of Rotational Tunneling Simulation of a Quantum System at Finite Temperatures”; Quantum Aspects of Molecular Motion in Solids, (Berlin 1987).
5)   Robert Eisberg and Robert Resnick, Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles, (New York 1974)
6)   Elizabeth Corcoran, “Diminishing Dimensions” Scientific American, November 1990, p.130.
7)   ibid. p.129.
8 )   ibid. pp. 128-129.

Quantum Tunnel of Love originally appeared in issue 8a,9a/92 of Bound for Sound.
Thanks to Marty DeWulf, the man with the best audio perception on our planet, for long ago granting me permission to use the article.

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