(Roughly) Daily

In the summer of 1925, a young Werner Heisenberg retreated to Helgoland in the North Sea and reemerged with the first full-fledged version of quantum mechanics. A century later, the theory’s meaning remains unsettled. Charlie Wood joined a group of physicists in Helgoland to take stock of the theory on its centennial…

Happy 100th birthday, quantum mechanics!” a physicist bellowed into a microphone one evening in June, and the cavernous banquet hall of Hamburg’s Hotel Atlantic erupted into cheers and applause. Some 300 quantum physicists had traveled from around the world to attend the opening reception of a six-day conference marking the centennial of the most successful theory in physics. The crowd included well-known pioneers of quantum computing and quantum cryptography, and four Nobel Prize winners.

“I feel like I’m at Woodstock,” Daniel Burgarth of the University of Erlangen-Nuremberg in Germany told me. “It’s my only chance to see them all in one place.”

One hundred years to the month had passed since a 23-year-old postdoc named Werner Heisenberg was driven by a case of hay fever to Helgoland, a barren, windswept island in the North Sea. There, Heisenberg completed a calculation that would become the heart of quantum mechanics, a radical new theory of the atomic and subatomic world.

The theory remains radical.

Before quantum mechanics hit the scene, “classical” physics theories dealt directly with the stuff of the world and its properties: the orbits of planets, say, and the speeds of pendulums. Quantum mechanics deals in something more abstract: possibilities. It predicts the chances that we’ll observe an atom doing this or that, or being here or there. It gives the impression that particles can engage in multiple possible behaviors at once, that they have no fixed reality. So physicists have spent the last century grappling with questions like: What is real? And where does our reality come from?…

Wood recounts the genesis and development of the theory and considers some of the vexing questions that remain: e.g., the many-world interpretation, the place (?) of gravity in the theory, et al. He concludes with a quote from Robert Spekkens, a physicist at the Perimeter Institute (whose work illustrates Lawrence Krause‘s observation that “At the heart of quantum mechanics is a rule that sometimes governs politicians or CEOs – as long as no one is watching, anything goes”): “We’re privileged to live at a time when the great prize of making sense of quantum theory is still there for the taking.”

Eminently worth reading in full: “‘It’s a Mess’: A Brain-Bending Trip to Quantum Theory’s 100th Birthday Party” from @walkingthedot.bsky.social‬ in @quantamagazine.bsky.social‬.

See also: “Physicists Can’t Agree on What Quantum Mechanics Says about Reality“

* Niels Bohr

###

As we wrestle with reality, we might send relativistic birthday greetings to one of quantum theory’s pioneers, Erwin Schrödinger; he was born on this date in 1887. A physicist, Schrödinger took Louis de Broglie‘s concept of atomic particles as having wave-like properties, and modified the earlier Bohr model of the atom to accommodate the wave nature of the electrons, which he instantiated in the Schrödinger equation, which provides a way to calculate the wave function of a system and how it changes dynamically in time. It was the basis of the work that earned him the Nobel Prize in 1933. And he coined the term “quantum entanglement” in 1935.

But surely Schrödinger is most widely known for creating the thought experiment we all know as “Schrödinger’s Cat” (and here).

source