The birth of quantum mechanics is often traced to a solitary 1925 retreat on Helgoland, where Werner Heisenberg conceived a theory that would dominate physics. At its core was a focus on what observers measure—a insight that, while brilliant, entangled the field in metaphysical quandaries for decades. Questions like "What defines an observer?" and "Does reality depend on being observed?" have fueled debates about Schrödinger's cat, Wigner's friend, and the very fabric of existence. But according to University of Oxford physicist Vlatko Vedral, it's time to cut the Gordian knot: observers are a misleading relic, and so are particles, space, and time.

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In a provocative analysis, Vedral argues that quantum theory already holds the answers—we just need to embrace its full implications. The key lies in entanglement, which Schrödinger dubbed quantum mechanics' "characteristic trait." When two quantum systems link, measuring one instantly reveals properties of the other. Vedral contends that what we call "observation" is merely entanglement between systems—no conscious observer required. This reframing dissolves paradoxes like Wigner's friend, where descriptions of reality clash between an experimenter inside a lab and one outside. "There is no 'ultimate' observer," Vedral writes. "There are no observers at all."

"I take a more radical view: space and time don’t exist at all. Like 'observers,' they are convenient labels—bookkeeping devices—but there are no physical entities corresponding to them."

This perspective shifts focus to quantum fields, entities that pervade all space and are governed by tables of values called q-numbers. Unlike classical numbers (c-numbers), q-numbers represent probabilities and superpositions, forming the true bedrock of reality. Vedral points to "ghost" photons in quantum electrodynamics—undetectable modes predicted by theory—as evidence. Alongside colleague Chiara Marletto, he proposed a 2023 experiment where electrons in superposition could entangle with these ghosts, detectable through subtle measurements. If successful, it would confirm that particles aren't fundamental; only their q-numbers are real.

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Experiments already hint at this unreality. In 2004, researchers demonstrated that single photons split between locations violate Bell's inequality—proof of "self-entanglement." Vedral and Jacob Dunningham have since outlined how to test this with massive particles like electrons, challenging the particle-centric view. But Vedral's vision goes further: space and time, he argues, are also illusions. General relativity describes gravity as the curvature of spacetime, but Vedral reimagines it as the quantum gravitational field bending other fields (like electromagnetism), with spacetime as a mere conceptual grid. Quantizing gravity, then, means upgrading it to q-numbers—not quantizing spacetime itself.

The implications cascade into uncharted territory. Vedral questions why quantum Hamiltonians—equations governing field interactions—mix q-numbers with classical constants like the speed of light. Making all values q-numbers could unveil new quantum fields, detectable if they weaken entanglement between particles. As physicist David Deutsch suggested in the 1980s, this might reveal a universe of infinite layers: "q-numbers all the way down," echoing the whimsy of cosmic turtles but grounded in testable science.

For developers and engineers, this isn't just philosophy. Vedral's framework could influence quantum computing, where entanglement is a resource, and AI, where quantum-inspired algorithms handle uncertainty. By eliminating observers, it simplifies models of quantum systems; by demoting particles, it aligns with field theories underpinning semiconductor physics. Pending experiments—like those probing ghost entanglement or gravitational q-numbers—could yield practical insights into error correction or new materials. In Vedral's quantum reality, the path forward isn't about adding complexity but stripping away illusions, revealing a cosmos where fields and their entwined probabilities are the only truths.

Source: Adapted from Vlatko Vedral's article in New Scientist.