In the ever-expanding landscape of quantum physics, reality is often stranger—and more thrilling—than science fiction. Welcome to the “quantum zoo,” a term now affectionately used by physicists to describe the menagerie of quantum states that emerge when electrons, in large numbers, interact under just the right conditions. These states aren’t just theoretical playthings. They could hold the key to next-generation technologies, including a long-sought goal: the elusive, error-resistant topological quantum computer. Now, in a major leap forward, researchers have uncovered more than a dozen never-before-seen quantum states, enriching the zoo and revealing exotic new physics—all without the use of a single external magnet.
This groundbreaking discovery, published on April 3, 2025, in Nature, was spearheaded by Xiaoyang Zhu, the Howard Family Professor of Nanoscience at Columbia University. His team’s achievement isn’t just an expansion of quantum state taxonomy. It’s a reimagining of what’s experimentally possible in the quantum realm—an ambitious detour through the strange backroads of electron behavior, made possible by a peculiar material and a twist of fate… or rather, a twist in the material itself.
A Glimpse into Quantum Wilderness
The core of this work lies in a seemingly paradoxical fact of quantum matter: when electrons—those tiny, negatively charged particles—move collectively, they don’t just follow the rules of the individual. Instead, they create entirely new rules, sometimes forming quantum states with properties more akin to collective creatures than particles.
For decades, many of these states remained theoretical, existing only in mathematical equations and computer simulations. Physicists predicted their existence with elegant formulas, but real-world materials refused to cooperate. It was as though the animals of the quantum zoo were only visible in shadow, their footprints barely detectable. Now, researchers are finally beginning to open the gates to this zoo and shine a light inside.
“It’s astonishing,” said Zhu. “Some of these states have never been seen before. And we didn’t expect to see so many either.”
What makes these states particularly tantalizing is their potential application in quantum computing—specifically, the holy grail of quantum computing: topological quantum computation. Unlike current quantum computers, which are fragile and error-prone, topological systems could protect quantum information by encoding it in the very fabric of space and time—making them extraordinarily resilient to noise.
But this dream has had one very stubborn obstacle: magnets.
Quantum Computing’s Magnetic Problem
Current methods for creating topological states often rely on magnets. That’s because magnetic fields help organize electrons into the kinds of arrangements that allow quantum weirdness—like fractional charge and entanglement—to flourish. The problem is, many of the most promising quantum materials, including superconductors, are incompatible with magnetic fields. Magnets disrupt them, causing them to lose their precious quantum coherence.
So, how do you build a magnet-free topological quantum computer?
The answer, it turns out, may lie in a wonder material called twisted molybdenum ditelluride. When layered and rotated just the right way, this atomically thin material conjures an internal magnetic field all on its own, eliminating the need for external magnets.
It’s not science fiction. It’s moiré magic.
The Moiré Revolution: Geometry Meets Quantum
To understand how this works, picture two sheets of chicken wire placed one atop the other. Now twist one sheet slightly. The result is a new pattern called a moiré pattern—a large-scale interference pattern formed by the overlay of two smaller patterns.
In the world of quantum materials, this trick is done with 2D layers of atoms. Stack them, twist them ever so slightly, and suddenly the electrons moving through these layers feel an entirely new geometry, one that bends and breaks the rules of ordinary physics. These moiré patterns give rise to frustration, symmetry breaking, and unexpected orders—ideal breeding grounds for quantum oddities.
“Twisting these materials essentially rewrites their quantum behavior,” explained Yiping Wang, a postdoctoral fellow at Columbia and lead author of the study. “The electrons begin to behave collectively, forming new quasiparticles, new interactions, and new kinds of order we’re just beginning to understand.”
The result? Topological states with fractional quantum charges, stable without magnets, and ready for experimentation.
The Ghost of Hall: A Quantum Ancestry
To appreciate the strangeness of these new states, one must journey back to a venerable 19th-century discovery: the Hall effect. In 1879, Edwin Hall observed that when a current flows through a metal strip in a magnetic field, the electrons bunch up along one edge, creating a measurable voltage—one that changes predictably with the strength of the magnetic field.
A century later, this was transformed into something far more bizarre: the quantum Hall effect, observed at ultracold temperatures and in two-dimensional systems. Instead of a smooth voltage increase, the voltage jumps in quantized steps—tiny plateaus linked directly to the fundamental charge of the electron.
Then came something even stranger: the fractional quantum Hall effect. Here, the quantum jumps weren’t full units but fractions: one-third, two-thirds, even one-fifth of an electron’s charge. How could this be? After all, electrons are indivisible.
Nobel laureate Horst Stormer explained this in his 1998 Nobel lecture: “Many electrons, acting in concert, can create new particles having a charge smaller than the charge of any individual electron. This is not the way things are supposed to be… And yet, none of these electrons has split up into pieces.”
These fractional charges, it turns out, are quasiparticles—emergent entities that act like particles but are really the collective behavior of many electrons. And they’re exactly the sort of entities needed for topological quantum computation.
A Magnet-Free Fractional Leap
In 2023, physicist Xiaodong Xu at the University of Washington—collaborating with Columbia’s Department of Energy-funded Center for Programmable Quantum Materials—made a stunning discovery. By twisting layers of molybdenum ditelluride, he and his team created a material that exhibited the fractional quantum Hall effect without any external magnet. The effect was “anomalous,” meaning it came from an internal magnetic-like interaction.
Xu’s students, Jiaqi Cai and Heonjeoon Park, led the work, which uncovered two rare fractional quantum anomalous Hall (FQAH) states, the first of their kind. Their findings opened the door. Zhu’s team charged through it.
The Pump-Probe Breakthrough
The key to Zhu’s discovery was a technique known as pump-probe spectroscopy, refined by Simons Fellow Eric Arsenault. In this method, a laser pulse temporarily melts the quantum state, nudging the system out of its equilibrium. Then, a second pulse measures how the material responds as it reforms, by detecting changes in its dielectric constant—a measure of how strongly electrons interact.
“It’s like startling a sleeping animal to see what it does when it wakes up,” said Arsenault. “These states are shy, hidden in the ground state. But when you disturb them just right, you can coax them into revealing their structure.”
And reveal they did. When Wang ran the experiments during Zhu’s absence, she expected to see a few fractional states. Instead, the data lit up with dozens—some predicted, others completely new. “It was like discovering a whole ecosystem we didn’t know existed,” Wang said.
Among the states were those associated with non-Abelian anyons, exotic quasiparticles that can braid together in spacetime and retain information through their topology—a critical ingredient for topological quantum computing.
“These are the building blocks we’ve been searching for,” Zhu said. “And now we know how to find them.”
Beyond Ground States: Time as a Dimension
Pump-probe spectroscopy revealed not only the lowest-energy configurations of these quantum states but also how they evolve over time—adding a temporal dimension to our understanding of quantum materials.
“It feels like we’ve entered a new dimension—time—to explore correlation and topology in the ground state,” Wang noted. “They just keep surprising us, especially when we push them out of equilibrium.”
This temporal lens may be the next great advance in quantum state exploration. Not only does it offer a way to detect subtle and ephemeral quantum features, but it also allows researchers to study how states transform—key for building and controlling quantum circuits in the future.
A Growing Quantum Menagerie
With dozens of new states added to the quantum zoo, the real work now begins. Each state is like a newly discovered species—complete with unique behaviors, preferences, and potential uses. Some may help realize topological qubits; others may remain curious oddities, awaiting further understanding.
“This is just the beginning,” said Zhu. “We don’t yet know what many of these states are, exactly. We have to classify them, study them, and test their robustness. But the door is wide open now.”
The hope is that Zhu’s team—and others inspired by their work—will use these techniques to uncover even more states, in more materials, with more useful properties. “We hope these results and our technique inspire others to explore,” said Zhu.
Conclusion: The Quantum Jungle Beckons
There was a time when electrons were thought to be indivisible, predictable, and boring. Now we know they are anything but. Under the right conditions, electrons collaborate to form new types of matter—states that defy our classical understanding and may power the technologies of tomorrow.
Zhu’s discovery doesn’t just expand the quantum zoo. It redefines its terrain, removing one of the biggest obstacles—magnetism—and lighting a path toward the magnet-free, topologically stable quantum computers scientists have dreamed of for decades.
In this newly unlocked wilderness of fractional quantum states, the adventure is only beginning. Somewhere, among these emergent species of quantum matter, the key to error-proof quantum computing may already be waiting—crouched just beyond the edge of our understanding, ready to be tamed.
Reference: Yiping Wang et al, Hidden states and dynamics of fractional fillings in twisted MoTe2 bilayers, Nature (2025). DOI: 10.1038/s41586-025-08954-8