A Microscopic Step Closer to Creating Schrödinger’s Cat for Real

A tale as old as quantum time: a cat is sealed in a box, suspended between life and death until someone opens the lid. Schrödinger’s infamous thought experiment wasn’t just feline cruelty—it was designed to explain one of the strangest ideas in quantum mechanics, superposition, the notion that an object can exist in two states at once or a cat can be both dead and alive. While countless experiments have confirmed that tiny particles can exist in such overlapping states, physicists have long wondered: is the same possible for larger, warmer, and messier systems—like cats? (or coffee machines or people reading this article)

In most lab setups, scientists create quantum systems by cooling everything to nearly zero. High temperatures were thought to destroy quantum behavior. But in a new study, a team of physicists at the University of Innsbruck showed that extreme cooling isn't always necessary. They prepared a Schrödinger’s cat state, a quantum system superposed between two distinct outcomes, at a temperature 90 times higher than usual.

These findings could help scientists build ultrasensitive sensors and test the limits of quantum theory. They may bring us closer to answering one of the oldest questions in physics: Where does the quantum world end and the classical one begin? Spoiler: we still don’t know, but it may be farther out than we thought.

The Innsbruck built a quantum system using a superconducting microwave cavity, a tiny metallic box designed to trap electromagnetic waves, like an echo chamber for microwaves. They wanted to see if they could create a quantum state from a system clouded by thermal noise.

Heat introduces randomness, called thermal noise, into quantum systems, making quantum effects harder to see, like trying to listen to a whisper in a crowded, noisy room. The quieter and more controlled the environment, the easier it is to hear clearly. Similarly, quantum systems usually need to be quieted down by intense cooling.

At room temperature, quantum systems generally exist in a mixed state. A mixed state is when a quantum system has no definite configuration. It exists as a combination of many possible quantum states at once. Think of it as looking at a blend of multiple pictures instead of one sharp image. On the other hand, a pure state is a system in one specific, well-defined quantum state with no uncertainty, like a perfectly sharp photograph.

“It started as a casual conversation over coffee with my colleague,” explained Gerhard Kirchmair, one of the study’s senior authors. “We deliberately added thermal noise to the cavity, and made it start in a mixed state, the question was if we could create a quantum cat state from something so imperfect?”

Cat states are interesting because they are easy to interpret. They represent a system in two macroscopically distinct states at once. In this experiment, for example, the cat state lives in the resonator and takes the form of two opposing electromagnetic oscillations. 

The team used carefully crafted pulses called unitary operations to coax the resonator system into the cat state. Amazingly, clear signs of quantum behavior emerged without removing any noise or messiness. They saw interference fringes, delicate patterns indicating that two different quantum states were overlapping in superposition.

“We believed in the theory,” Kirchmair said. “But nobody had demonstrated this so far. And if you asked 10 physicists whether this would be possible, the outcome would probably be 50-50—at least until they start thinking carefully about it.”

This technique could make a promising difference in quantum sensing, especially with nanomechanical oscillators, tiny devices that vibrate at specific frequencies, acting like microscopic tuning forks. They are used for sensing, measuring, and processing information at the nanoscale. 

Nanomechanical oscillators can be made from carbon nanotubes, graphene membranes, or nanobeams. While macroscopic compared to atoms or photons, they can still behave quantum mechanically under the right conditions, such as when cooled close to their ground state. These systems operate at the edge of the quantum and classical worlds.

"If we could put them into quantum cat states, we might open new paths to practical sensors and foundational quantum research." Said Kirchmair. Because cat states contain interference patterns incredibly sensitive to small changes, they could detect signals that classical sensors might miss.

Pushing systems into the quantum regime requires extreme cooling. “For large mechanical systems, it's actually very tricky to get them to the cold ground state,” Kirchmair said. “So, any technique that helps avoid that requirement could make quantum sensing more practical.”

These findings also touch on a deeper question: what does it really mean for a system to be quantum or classical?

Traditionally, physicists have assumed that quantum coherence—the defining feature of quantum systems—falls apart as systems get larger, warmer, or more chaotic. But this study shows that even starting with a hot, noisy system, you can still carve out a space for quantum behavior to emerge.

“How large or hot can a system be made before it loses its quantum properties?” Kirchmair asked. “Can I make a large particle, hundreds of micrometers big, something I could almost see with my bare eye, and still prepare it in a quantum superposition?”

“We don’t know where the line is,” Kirchmair said. “Is there even a strict dividing line between the quantum and classical worlds? Or is it just about building a good enough box to isolate your system?”

In most quantum experiments, that “box” protects the system from outside noise, heat, or measurement. But as Kirchmair explained, the real question is whether that box can scale. “Can I build a large enough box to fit my experiment inside and still see quantum effects? Or is there something fundamental that says even if the box is perfect, just being large or warm will somehow destroy the quantum behavior? I think we don’t have the answer to that yet.”

That’s why cat states are such useful tools. They embody quantum superposition in a testable form. If such states can persist in large, high-temperature environments, it suggests the boundaries of quantum mechanics may be wider than expected.

“In Schrödinger’s original idea, the cat was warm and alive,” Kirchmair said. “So, in a sense, our experiment is a little closer to the spirit of his actual thought experiment, showing you can create quantum states from conditions far from absolute zero.”

While most quantum experiments aim to build smaller, colder, and more ideal systems, this research suggests another direction: making the quantum weirdness work under real-world conditions.

We haven’t gotten the cat alive and dead just yet, but we are definitely getting warmer if you know what I mean.