This is a salon-style discussion hosted by MIT computational biologist Manolis Kellis, featuring Harvard theoretical physicist and philosopher Jacob Barandas and podcast host Curt Jaimungal, recorded at Harvard before a live audience of over 70 people. The conversation ranges across quantum foundations, the nature of observers, the reality of wave functions and fields, the interpretation of quantum mechanics, the hard problem of consciousness, and the practical future of quantum technologies. Jacob’s core argument is that the standard textbook formulation of quantum mechanics is purely instrumentalist—it only predicts measurement outcomes and says nothing about what exists between measurements—and that most physicists misleadingly present interpretive claims (like particles being “in two places at once”) as established fact when they are not.
What Quantum Theory Actually Says (and Doesn’t Say)
The standard Dirac–von Neumann axiomatic formulation of quantum mechanics is purely instrumentalist: it provides a recipe for predicting the probabilities of measurement outcomes, but it does not describe what is physically happening between measurements.
When textbooks say an electron “orbits” a nucleus or a photon “emits” from an excised atom, these are just colorful fables added for pedagogical comfort. The formalism itself only connects preparation procedures to measurement results.
Jacob’s key claim: every time a physicist says “quantum physics has demonstrated that a particle can be in two places at once,” they are lying—not because it is definitely wrong, but because no interpretation except possibly many-worlds actually asserts this, and even that is contested.
The Copenhagen Interpretation and Its Limits
The Copenhagen interpretation, as articulated by Heisenberg, holds that classical objects (including observers) have physical reality describable in three-dimensional space, but quantum systems do not—the mathematical formalism (wave functions, Hilbert spaces) is a mental construct, not a description of something physically real.
There is no physical picture of what happens between measurements; the theory simply cannot provide one, and according to Copenhagen, we should not ask.
This was motivated by a worry that the mathematical apparatus of quantum theory was so constraining that no ontological picture could be made compatible with it.
Wave Functions: Physical Fields or Mathematical Tools?
Jacob argues that wave functions are not physically real in the way that chairs or even electromagnetic fields are.
Electromagnetic fields are intensities distributed in physical space; they propagate energy and signals. They are “beables” in John Bell’s terminology—things that really exist.
Wave functions, by contrast, live in high-dimensional configuration space (3N dimensions for N particles), not in physical three-dimensional space. For a single particle the wave function can be loosely visualized as a field in 3D, but for two particles it already requires six dimensions, and so on.
Schrödinger originally took the wave function seriously as a physical wave in this abstract parameter space, even suggesting it might be the seat of reality (an embryonic many-worlds view), but he recanted in 1928 under the influence of Max Born’s probabilistic interpretation.
Jacob sees the wave function as analogous to gauge potentials in electromagnetism: mathematically useful but not uniquely defined, and therefore not physically real. Just as infinitely many gauge potential configurations correspond to the same electric and magnetic fields, the wave function is a computational device, not an ontological entity.
Beables vs. Observables
John Bell introduced the term “beables” (as opposed to “observables”) to describe things that really exist physically, as opposed to quantities that observers measure.
Electromagnetic fields are beables; gauge potentials and wave functions are not.
Jacob does not claim to know what the fundamental beables of nature are—they might be quantum fields, or something deeper—but he argues that whatever they are, they should be things that exist in physical space, not abstract mathematical spaces.
He uses the analogy of wetness: wetness is not fundamental (it does not exist at the level of individual water molecules), but it is nonetheless real at an emergent level. Similarly, humans and chairs are non-fundamental but perfectly real beables.
The Historical Origin of Quantum Mechanics’ Anti-Realist Stance
In the early 1920s, physicists tried and failed to find laws that would make the Rutherford atom picture (electrons orbiting nuclei) work empirically.
Bohr came to believe that electron orbits did not exist. Heisenberg, influenced by Bohr, made a radical philosophical move: banish all physical pictures and build a theory solely from quantities that are in principle experimentally measurable.
Heisenberg developed matrix mechanics in 1925 while suffering from severe hay fever on the island of Heligoland—a theory without pictures, just raw mathematics. Einstein called it “a great quantum egg.”
Schrödinger then reintroduced pictures through wave mechanics, deriving his wave function from the Hamilton–Jacobi formulation of classical mechanics—a wave-like mathematical quantity that no one had previously considered physically real. The wave function was thus a descendant of a classical mathematical appurtenance, not a discovery of a new physical entity.
Interpretations of Quantum Mechanics
Instrumentalist/Textbook (Dirac–von Neumann): Only measurement outcomes and their probabilities are meaningful. No picture of underlying reality is provided or needed.
Copenhagen: Classical objects are real; quantum systems are described by mathematics that should not be taken as representing physical reality. Observers and measurements play a fundamental axiomatic role.
Pilot Wave (de Broglie–Bohm): There are real particles with definite positions at all times, guided by a wave function (the “pilot wave”). The wave function is still not a physical wave in 3D space, but the particles are real corpuscles. Bohm’s 1951 version introduced decoherence to solve the problems that destroyed de Broglie’s original 1920s version.
Many Worlds (Hugh Everett): The wave function is physically real, and all branches of a superposition are equally real—each representing a different “world.” Jacob is skeptical: if many worlds were really doing the parallel computations, quantum computers should speed up far more calculations than they actually do.
Jacob’s own view (Indivisible Stochastic Processes): Physical systems have actual physical configurations (beables in physical space), but the laws governing them are non-Markovian in a particularly strong sense called “indivisibility”—the evolution cannot be broken into lawful sub-steps. This framework naturally produces interference-like phenomena and is mathematically dual to quantum mechanics, potentially offering both a metaphysical picture and new practical applications.
Decoherence and the Observer Problem
Decoherence is the process by which a quantum system interacting with a large, complex environment (a measuring device, the air, the moon) loses its interference effects and begins to behave classically.
Bohm introduced this concept in 1951, calling it “the destruction of interference in the process of measurement.”
It eliminates the need for a conscious observer: any sufficiently large system with many degrees of freedom can cause decoherence. There is no sharp line between “observer” and “non-observer”—it is a fuzzy gradient, roughly around the scale of large molecules (thousands of atoms, such as large sugar molecules or polymers) under normal temperature conditions.
At very low temperatures, macroscopic quantum phenomena like superfluidity and superconductivity can occur, showing that size alone is not the deciding factor—isolation and temperature matter too.
The concept of an “observer” was required by the original axiomatic formulation of quantum mechanics, but interpretations like Bohmian mechanics and many worlds attempt to eliminate the observer as a fundamental primitive, treating everything as physical systems interacting with other physical systems.
Non-Locality and Entanglement
Entangled particles exhibit correlations that appear to involve instantaneous (“non-local”) influences, as in the EPR thought experiment: two particles are separated, and measuring the spin of one seems to determine the spin of the other instantaneously.
Jacob argues that quantum field theory does not resolve this problem. Having a single electron field everywhere does not help, because entanglement can occur between different types of fields (e.g., a photon and an electron).
The apparent non-locality depends crucially on the role of observers doing interventions. When the story is told in terms of atoms interacting with atoms—without agents and measurements—the causal non-locality becomes much murkier.
John Bell attempted to formulate a version of his theorem that would demonstrate causal non-locality without relying on agents and interveners (his 1975 “local beables” paper), but Jacob argues Bell did not clearly succeed.
Schrödinger himself recognized the “regress problem” of entanglement: when an entangled system interacts with another system, which interacts with yet another, the entanglement spreads indefinitely. He called entanglement not one but the defining feature of quantum theory.
The Markov Approximation and Jacob’s Alternative Framework
All known physics before quantum mechanics was Markovian: the present state determines the future; the past is irrelevant once you know the present. This was not recognized as an assumption—it was simply how all laws worked.
Jacob’s approach uses “indivisible stochastic processes,” a particularly strong form of non-Markovianity where the evolution over any duration cannot be broken into lawful sub-durations. This is a much more general class of processes than Markov processes.
Indivisible stochastic processes naturally exhibit interference-like phenomena and are mathematically equivalent (dual) to quantum mechanical systems. This provides a possible metaphysical picture: quantum mechanics may be what you get when you give classical-like physical configurations non-Markovian indivisible laws.
This framework also has potential practical applications: difficult non-Markovian stochastic processes (in finance, biology, economics) might be efficiently simulable on quantum hardware by mapping them to equivalent quantum systems.
Quantum Computing: What Are They Good For?
Contrary to popular belief, quantum computers do not simply “try all possibilities simultaneously.” They provide speedups for only a narrow set of problems.
Known applications include cracking RSA encryption (prime factorization) and efficiently simulating quantum systems.
Jacob’s framework suggests another potential application: simulating complex non-Markovian stochastic processes on quantum hardware, which could be useful across science, economics, and finance.
He argues that quantum foundations and philosophy of physics are significantly underfunded relative to their contributions: decoherence, entanglement, GHZ states, the no-cloning theorem, quantum teleportation—all came from foundational work by a tiny number of people. If the field received royalties for every use of these concepts, it would be extremely well-funded.
Consciousness and Quantum Mechanics
The “hard problem of consciousness” (coined by David Chalmers) asks why physical brain processes are accompanied by subjective experience—why there is “something it is like” to see red, feel pain, etc.
The “easy problem” (still very hard) is explaining the behavioral and functional aspects of consciousness—building models that predict what conscious beings do.
Frank Jackson’s “Mary’s room” thought experiment illustrates the gap: Mary is a brilliant scientist who knows everything physical about color vision but has never seen color. When she finally sees red, she learns something new—the subjective experience—that no amount of physical information could have given her.
Jacob’s view: even if quantum mechanical processes play a role in brain function, this does not solve the hard problem. Knowing that certain quantum processes occur in the brain and modeling them perfectly would still not explain why they are accompanied by subjective experience. The hard problem may be unsolvable in principle.
He is open to the possibility that we are all “P-zombies” (philosophical zombies)—beings that behave exactly as if they are conscious but lack internal subjective experience. There is no experiment that could distinguish a world of P-zombies from a world of truly conscious beings, because by construction they are behaviorally identical.
Quantum Effects in Biology
The audience and panel discuss whether quantum effects play a functional role in biological systems.
Manolis Kellis suggests oxidative phosphorylation in mitochondria as a candidate, and mentions that quantum effects in olfaction (the sense of smell) have been proposed and have some experimental support.
Jacob notes that quantum biology is a legitimate field, but cautions against invoking quantum mechanics merely because a biological system is poorly understood. The cases where quantum effects are genuinely exploited in biology are specific and limited.
The audience discusses microtubules in neurons as a proposed site of quantum effects related to consciousness, but Jacob’s position is that even if true, this would not address the hard problem.
The Historical Shift Away from Foundations
Jacob laments that physics departments no longer engage in the kind of foundational, philosophical discussion that was common in the early 20th century.
In the 1920s–1940s, physicists like Bohr, Heisenberg, Einstein, and Schrödinger were deeply engaged with philosophy—with the Vienna Circle, with Kant, with positivism. They argued about the interpretation of quantum theory as part of doing physics.
After World War II, the center of physics shifted to America, and the culture changed: increased funding and pressure to produce practical results made philosophical discussion seem like a luxury. The result is that most physicists today are not trained to think about foundations, and the field is the poorer for it.
Jacob argues that the underfunding of quantum foundations and philosophy of physics is a mistake, given how many foundational insights (decoherence, entanglement, no-cloning, etc.) have turned out to be essential for modern quantum technologies.
Weak Measurements
Weak measurements are a protocol in which a very gentle interaction with a quantum system extracts minimal information about it, avoiding the full “projective collapse” of standard measurements.
The protocol requires many identically prepared copies of a system (e.g., 10,000), each measured very gently. The aggregate data yields a number (a matrix element of a self-adjoint operator), but the physical meaning of this number is disputed.
Jacob notes that while the experimental protocol is real and the number has mathematical significance, what it tells us about the physical system is murky and essentially philosophical.
