Is Quantum Randomness Fundamental?
Introduction
Quantum measurements and observations are fundamentally random. However, randomness is in deep conflict with the deterministic laws of physics. Do hidden properties determine outcomes, so that they only appear random to us? Does our observation or consciousness act outside of physics to instantiate random change? Does the universe spit with each possible outcome manifested in a separate branch? These and other questions are still debated and unresolved. The answer boils down to the nature of time.
The Two Times
There are two very different conceptions of time and change. The first is the time of mechanics. Relativity describes change as a sequence of 3D slices across the time axis of a static “block universe” in 4D spacetime. Like the three dimensions of space, the time axis is fixed and has no preferred direction. Quantum mechanics describes a system by its time-dependent wavefunction, which is similarly deterministic and time symmetrical. Determinism means that the future, as well as the past, is set in stone and time is simply the playing out of fate. Time-symmetry means that there is no fundamental distinction between past and future.
The second time is the time of thermodynamics. The First Law of thermodynamics states that total energy is conserved, but the Second Law states that any spontaneous process irreversibly produces entropy. If two clay lumps are flung together and merge, their loss of kinetic energy is offset by their increase in heat. The total energy is conserved (First Law), but the dissipation of kinetic exergy is to ambient heat is associated with the production of entropy. Once exergy is dissipated to ambient heat, the process can never spontaneously reverse (Second Law). The conflict between mechanical and thermodynamic times expresses the problem of time’s arrow.
Physics’ Wrong Turn
Newton’s laws of classical mechanics express the conservation of momentum, but, significantly, not of energy. Newtonian mechanics accommodates friction, which irreversibly dissipates a system’s mechanical energy to heat. In 1833, William Rowan Hamilton redefined Newton’s empirical description of a system’s state in terms of elementary particles. Elementary particles have no internal structure and no internal energy or heat. Heat is simply the average kinetic energy of the elementary particles. With no thermal energy, mechanical energy is conserved. Friction is simply regarded as the dispersion of kinetic energy to particles too small to resolve. We perceive this as heat, but Hamiltonian mechanics regards the dispersion of kinetic energy as microscopically reversible. If the clay particles’ motions were reversed after the clay lumps collided, their energies would coalesce, and the clay lumps would fly apart. The only reason we do not see this happen is because it is astronomically improbable, but no laws of physics would be violated, and given sufficient time, it would occur, eventually. The reversibility of time is a consequence of what I call the Hamiltonian Conceptual Framework (HCF).
Quantum mechanics fundamentally changed the description of mechanical systems. It describes a quantum state by its wavefunction. The HCF interprets the wavefunction as a complete description of the physical state, as it existed in isolation prior to observation. The determinism of the wavefunction therefore implies that the physical state, as it exists in isolation and unobserved, is deterministic. The prevailing HCF interpretation of Quantum mechanics is the Copenhagen Interpretation.
Erwin Schrödinger sought to highlight the absurdity of the then-emerging Copenhagen Interpretation. He considered a perfectly isolated system comprising a radioactive particle and its measurement apparatus (Figure 1). For added drama, he used a cat for the measurement device. If the particle decays, the cat dies. At observation, we either find the cat dead, indicating that the particle decayed, or we find it alive, indicating no decay. The outcome of observation is intrinsically random.
The determinism of the physical state means that, prior to the cat’s observation, while the system was isolated and unobserved, it must have existed as a physically superposed state of undecayed-decayed particle and live-dead cat. Explaining the random collapse of a superposed physical state to the definite state at observation, and the unexplained role of the observer on physical collapse are unresolved questions at the core of the measurement problem.
Hugh Everett proposed an alternative HCF interpretation that avoids the absurdity of superposed cats and eliminates the measurement problem. In essence, his Many Worlds Interpretation says that everything that can happen does happen in separate branches of an exponentially branching universe. Even we, as observers, are split, with one split seeing a dead cat and the other seeing a live cat. From the subjective perspectives of our split selves, we perceive random wavefunction collapse. From the objective perspective of the universe as a whole, however, there is no random selection and the universe evolves deterministically. The Many Worlds Interpretation eliminates the random collapse of a superposed state to a single definite state, but in exchange it gives us an exponentially branching universe.
The Hamiltonian conceptual framework fails to accommodate entropy, irreversibility, and the arrow of time as fundamental. It demotes the well documented and universal laws of thermodynamics to a statistical approximation of physical reality. It resorts to mind-bending and untestable metaphysical hypotheses to explain the randomness of quantum observations. Imposing the Hamiltonian conceptual framework of classical mechanics onto thermodynamic and quantum mechanical systems marked wrong turns in the history of physics.
Physics, Reinterpreted
The WYSIWYG conceptual framework (WCF) resolves the measurement problem and time’s arrow, simply by reinterpreting physical reality as defined with respect to a system’s ambient surroundings. The WCF’s primary principle is that there are no hidden properties: “What You can See Is What You Get.” It recognizes that absolute zero does not exist, even in principle, and that no system is perfectly isolated from its ambient surroundings. Even the universe as a whole has a positive ambient temperature equal to its background microwave temperature of 2.7K. The WCF contextually defines the physical state by perfect reversible measurement (Figure 2). Exergy (work potential), ambient heat, and entropy are defined as objective contextual properties of state with respect to the system’s ambient surroundings.
Perfect measurement is reversible, but reversible measurement is not always possible. The Quantum Zeno Effect shows that a continuously measured (and measurable) state does not change irreversibly. The contrapositive is equally true: an irreversibly changing system is not continuously measurable. During an irreversible transition, a system is not continuously and reversibly measurable, and it does not exist as a WCF state. It is in transition between states, and irreversible time advances with the production of entropy. Between irreversible transitions, the system is continuously measurable and it exists as a state over reversible time. In Reinventing Time, I describe system time as a complex property of state, spanning real thermodynamic time and imaginary mechanical time.
In Schrödinger’s cat thought experiment, the system can momentarily exist in irreversible transition between states, during which it does not exist as a state. There is no superposed state of decayed-undecayed particle or live-dead cat; there is no observation-induced physical collapse; and there is no measurement problem. There is only the random and irreversible transition to a more stable quantum state.
Does any of this really matter? Recognizing the objective reality of irreversible dissipative processes and explaining their behavior in terms of fundamental physical principles is essential if we want to understand how nature really works. To advance physics beyond its current focus on states, we need a conceptual model that embraces irreversible dissipative processes and the spontaneous self-organization of dissipative systems. This requires nothing less than a major shift in our interpretation of physical reality.
The WCF is contextual, but it objectively defines physical reality with respect to a system’s actual surroundings, independent of observers or observation. Contextuality provides the foundation for time’s arrow and quantum randomness; it resolves the problem of quantum measurement; and, as described in The Arrow of Functional Complexity, it extends physics from a study of states to the study of dissipative systems and their evolution.
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For a full-text technical article on the WCF, see https://www.preprints.org/manuscript/202007.0469/v5
