Tales of the Quantum: Understanding Physics' Most Fundamental Theory

by Art Hobson

Energy is the ability to do work. OK, so what is work? In physics, work is done whenever a force (a push or pull) acts on an object while the object moves through some distance.

The general principle is: A system that is partly organized at the molecular level and that is given the opportunity to reorganize is highly likely to proceed to a less organized state. This is called the second law of thermodynamics.23

First, they are quantized—meaning, they are made of highly unified, spatially extended bundles of field energy called quanta. Each quantum is itself simply a disturbance in a universal field, analogous to a ripple that disturbs the smooth surface of a pond. This field-bundling feature obviously lends a particlelike aspect to quantum fields, because the bundles are somewhat like particles. Bundles can, for example, be counted, whereas the points filling a spatial volume cannot be counted. This countable, digital aspect of quantum fields is not found in classical fields.

Second, the various types of quantum fields include not only “force fields” for three of the four known forces (a quantum theory of the fourth force, gravity, is still a work in progress), they also include another quite unexpected category called matter fields. With matter fields, material objects such as electrons, protons, atoms, and molecules are brought within the field framework.

Suppose Hertz’s radio transmitter sends an EM wave to Mars, and that the travel time, at light speed, is 12 minutes. Energy must travel from sender to receiver because work must be done to cause the receiver’s electrons to vibrate, and work requires energy. Where is this energy during the 12-minute travel time? It’s not in the sender (which could be turned off after sending the message), and it’s not yet in the receiver. And energy never vanishes. So it must be in the space between sender and receiver, in the EM field.

Summarizing, rocks are made of quarks and electrons, whose interaction with the Higgs field provides 5% of the rock’s mass. The remaining 95% comes primarily from the strong force field that binds quarks together into protons and neutrons, and binds protons and neutrons together into nuclei. Ultimately, a rock is nothing but fields—fields you can kick.

According to quantum physics, not only force, but also matter arises entirely from fields.

Each quantum is an extended bundle of field energy, quanta are not necessarily small, they overlap in space, they are flexible not rigid, and they are delicate not indestructible.

What does quantum physics tell us about the possibility of “EM nothingness,” in which there are no EM phenomena of any kind—no photons, no electrically charged objects, no EM energy or EM fields of any kind. In this case, the EM field throughout this region of space would be precisely zero, with no uncertainty. Such a situation would violate Heisenberg’s principle, according to which all fields must maintain at least a minimal degree of randomness. So the EM field must exist, and it must have at least a minimal, randomly varying energy everywhere.

The EM vacuum field extends throughout the universe, even in regions between the galaxies where “nothing”—no thing—exists. In such vacuum regions, there are no photons, no charged objects, no EM forces, but there is, a minimal, randomly fluctuating EM field that satisfies the indeterminacy principle.

But if photons are not particles, how can we explain the particlelike impact points? Here’s how: Each photon is a spread-out wave, an extended bundle of field energy that comes through both slits and then fills the screen just before interacting with it. Each photon then interacts with the entire screen. But the screen is made of zillions of individual atoms. Because a photon cannot be subdivided, it must deposit its entire energy into just one of these atoms “chosen” randomly (Chapter 6). This atomic-level interaction is then amplified so that a tiny visible flash appears on the screen.

In a typical double-slit experiment with light, the pattern (and hence the pre-impact photon) is a few centimeters wide. Each photon contacts all the screen’s atoms within the pattern, filling the entire region, yet it must give up its energy to only one atom because it’s a unified quantum. But the photon only carries information about the overall striped pattern, not about any particular atom where it should interact. Hence, the selection of a particular atom is made randomly but within the confines of the overall pattern. The photon–atom interaction causes the photon to vanish.

How big is a photon? According to Louis de Broglie, a founding father of quantum physics, an individual quantum “fills all space” (see his statement quoted later). He was talking about electrons, but the same principle applies to photons. Quantum theory implies that every free (unconstrained) quantum is extended indefinitely in space and is not contained within any region of finite volume. So any talk of the size of a photon or of any other quantum must refer to some finite region within which the photon has a large probability (say, 99%) of interacting with a detector such as a viewing screen. How large, then, is such a high-probability region for a single photon?

Because “each photon interferes only with itself” (Dirac), the photons detected by this array must have had lateral extensions of at least 100 m. Radio photons, having longer wavelengths, can be far larger than 100 m. The Very Large Array near Socorro, New Mexico, in the United States, is the world’s largest radio telescope array. It stretches along a 36-kilometer line, and demonstrates the interference of radio photons over this distance, verifying that photons can be 36 kilometers wide.

The Event Horizon Telescope will focus on the giant black hole, with a mass of four million suns squeezed into a region the size of Mercury’s orbit, at the center of our Milky Way galaxy. It will observe processes taking place just outside the edge or “event horizon” of this black hole—the spherical surface from which nothing can escape. This will be by far the most extreme gravitational environment ever observed and will provide an ultimate testing ground for Einstein’s general theory of relativity. The photons detected by this combined system will be as wide as our planet, yet, when detected by a receiver, they will collapse instantaneously into a small region like the points of light

That is, electrons are to matter as photons are to EM radiation!

Quantized matter fields explain the absolute uniformity of microscopic matter. As far as we can tell, every electron is precisely identical to every other electron, every proton is identical to every other proton, all hydrogen-1 atoms (i.e., atoms with a nucleus of just one proton) are identical, and so forth. Why is this? The explanation remained a profound mystery until the discovery of matter fields showed that electrons are identical because every electron is a ripple in a single matter field that fills the universe. This not only explains the absolute identity of all electrons, it also represents another unification. The zillions of electrons, for example, are instances of one thing: the universal electron–positron field.

So electrons are not tiny particles at all: they are ripples in a field that fills the universe. Here is how Louis de Broglie put it memorably in 1924: The energy of an electron is spread over all space with a strong concentration in a very small region… . That which makes an electron an atom of energy is not its small volume that it occupies in space, I repeat it occupies all space, but the fact that it is undividable, that it constitutes a unit.

Reality is a set of space-filling fields with quanta rippling through and energy, like wind stirring a lake, generating the possibility of change, destruction, and creation.

failed to convince the physics community that quantum physics is entirely about fields. After all, Dirac’s equation, especially its quantized version, obviously described an extended matter field Ψ that was analogous to the EM field of Maxwell’s equations. Yet, most physicists continued to insist that this same entity Ψ, when it appeared in Schrödinger’s equation, described low-energy material particles. So the same physical concept, Ψ, somehow represented particles in Schrödinger’s equation but a field in Dirac’s equation, even though Schrödinger’s equation was simply Dirac’s equation restricted to the case of slow-moving electrons. It was as though slow-moving particles, by simply moving faster, somehow transformed into space-filling fields.

It’s important to use the right words. We’ve seen that the double-slit experiment must be understood in terms of quantized EM fields and quantized matter fields. This makes the term quantum field theory misleadingly superfluous. It’s all just quantum physics, and quantum physics is entirely about fields. It also makes the word particle superfluous and hugely misleading. There’s a simpler (fewer syllables) and far more accurate word: quantum. There are no particles. Do not imagine, when visualizing a photon or electron as a ripple in a field, that there is a tiny particle floating within the ripple. The ripple is the photon or electron. Fields are all there is.

This is why superconductors work: The paired-electron field causes photons to have mass and the EM force to have only a short range, and this neutralizes EM forces in the superconductor’s interior, so electrons move freely.

Imagine two protons smashing into each other as they do within the Large Hadron Collider, in slow motion, and at far higher energies than is possible at the Collider. We’ve seen that gravity is negligible at distances such as 0.1 nm (the distance across a hydrogen atom). But as our two protons get closer and closer, the forces between them increase, so the energy stored in their force fields increases. But energy has mass, so the masses of the protons increase as they get closer. This mass increase affects the gravitational force but not the EM force, causing gravitational attraction to increase enormously faster than the other forces as the protons get closer. Eventually, gravitational attraction exceeds all the repulsive forces, and the situation becomes unstable. Beyond this point, the distance between the protons continues to decrease spontaneously as their masses increase toward infinity. There must be something wrong with this picture, because an infinite mass would cause the entire universe to collapse!

Because large energies imply large masses, this pointlike nature of quanta at high energies implies infinities that ruin the theory. The string hypothesis avoids this high-energy pointlike structure by assuming that all quanta are strings. A string is a quantum that, on being squeezed at the highest energies into its smallest configuration, reduces to a one-dimensional loop, like a rubber band, rather than to a point. A loop configuration spreads the quantum out in just the way needed to prevent the infinities. This idea might lead to the perfect unification: All fundamental quanta might be strings that are ultimately identical, with the difference between them lying only in their manner of vibration.

So there’s a net inward force on each plate. This is the Casimir force. It exerts forces on metal plates in vacuum where there are no quanta. If the universe is made of particles, then what is it that presses inward against these plates in vacuum, where there are no particles?

Quantum interactions are individually random; but, like other random processes, the statistics of quantum processes over a large number of trials are approximately determinate.

quantum fields must oscillate at every spatial point. Even when the field is in its lowest energy or “vacuum” state having no quanta, it must vibrate randomly everywhere.

you should imagine the electron as a large balloon and the detection screen as a bed of nails: the electron extends over many nails but the interaction is going to occur at only one of them.

Mermin next argues that quantum fields are not real, but are merely “useful mathematical tools.” This leads him to question the reality of Maxwell and Faraday’s classical EM field, which is, after all, the same entity as the quantized EM field but simplified by ignoring quantization. He concludes that “classical electromagnetic fields are another clever calculational device.” Most physicists, however, view classical fields as properties of space itself. This leads Mermin to the further conclusion that “space and time … are not properties of the world we live in but concepts we have invented to help us organize classical events.” Space and time are not real? Apparently there’s a slippery slope in any argument that quantum entities are not real. It becomes difficult to find entities that are real, because, after all, everything is supposed to be ultimately quantum.

Most physicists accept the reality of space, time, and fields. If one accepts the reality of fields, it’s hard to see how one can reject the reality of quantized fields and thus the reality of various states of a quantum. A significant new argument emerged in 2012. Matthew Pusey and two colleagues proved that the epistemic interpretation of quantum states implies experimental predictions that contradict the predictions of standard quantum physics.14 Because scientists agree that the quantum predictions are correct, an interpretation that is inconsistent with those predictions is of no value.

Overshadowing all these details is the central notion that, as Carl Sagan put it, “Extraordinary claims require extraordinary evidence.”16 The claim that our most fundamental theory does not describe reality flies in the face of all previous scientific history and is extraordinary by any definition. We dare not adopt the nonrealist view without overwhelming evidence. It is one purpose of this book to demonstrate there is no evidence of this sort—no evidence that quantum physics is anything other than a consistent theory of the real, objective world.

Quite unlike the smooth, predictable Schrödinger evolution of a single quantum such as an electron, a quantum jump is a discontinuous and indeterminate alteration of a system’s quantum state that occurs when the system interacts with another system. If one of the systems is macroscopic, and if the change of this macroscopic system’s quantum state results in a macroscopic impression such as an observable flash, the interaction becomes a quantum measurement.

quanta exhibit the following superposition principle: If a quantum can be in any one of several different states, then it can be in all of them simultaneously.

Summary: Just as the electron matter field is a fermion field whose quanta are individual electrons, superconducting electrons form a boson field whose quanta are electron pairs. At low temperatures, these pairs are isolated energetically from the lattice and experience zero resistance. That’s how superconductivity works.

The photon, which moves along either path 1 or path 2, is in the following entangled superposition: “Path 1 contains the photon and path 2 contains the vacuum” superposed with “path 1 contains the vacuum and path 2 contains the photon.”