Hot Schrödinger’s Cat? Physicists Pull Off The Impossible In Quantum Experiment

The scientific team of the University of Innsbruck and the Austrian Academy of Sciences managed to create what are known as Schrödinger’s cat states inside superconducting microwave resonators, tiny, ultra-precise structures used in quantum experiments. Remarkably, they did so without cooling the system all the way down to its lowest possible energy state.

New Research Challenges The Zero-Temperature Myth

Quantum systems have long been thought to survive only at the edge of absolute zero. But new work from Austrian researchers suggests they may be less delicate than assumed. In an unexpected development, physicists have shown that quantum states, those strange, in-between conditions where particles occupy multiple states at once, can hold together in environments far warmer than conventional wisdom allows. Their findings push back against one of the longest-standing assumptions in the field: that heat and quantum effects simply can’t mix.

Schrödinger’s Cat But Not As We Know It

Most people interested in quantum physics will have come across the famous thought experiment. Schrödinger’s cat, hypothetically locked inside a box with a radioactive source and a deadly mechanism, sits in a limbo between life and death until someone lifts the lid. The idea was meant to highlight how absurd quantum mechanics can seem when applied to the everyday world.

Of course, no cats are involved in the lab. Instead, physicists use photons, atoms, or electronic circuits to build states that mimic this paradoxical quantum system, which exists in two or more states simultaneously. These cat states are used to explore the limits of quantum theory and underpin some of the principles behind emerging technologies like quantum computing.

Keeping The Schrödinger’s Cat Warm

Here’s where the new study gets interesting. Normally, quantum experiments are carried out as close as possible to absolute zero, the coldest temperature allowed by physics, where all thermal motion stops. That’s because heat, however slight, is usually enough to wreck the fragile superpositions that define quantum states.

But the Innsbruck researchers asked a simple but bold question: Must these states really start from cold?

The answer is no.

Using a device called a transmon qubit embedded in a microwave resonator, the team demonstrated that cat states can be generated from thermally excited, “hotter” conditions. Rather than beginning from the ground state, they let the system sit at a higher energy level, 1.8 Kelvin, to be exact (still cold, but significantly warmer than what’s typically used). That’s around sixty times the usual operating temperature for such experiments. The key was tweaking their experimental methods to suit these hotter conditions. With adapted protocols, the team was able to generate clear quantum interference patterns, proof that quantum coherence was still alive and well despite the elevated temperatures.

As Gerhard Kirchmair, the lead researcher, explained: “Our work reveals that it is possible to observe and use quantum phenomena even in less ideal, warmer environments. If we can create the necessary interactions in a system, the temperature ultimately doesn’t matter.”

Why It Matters

The implications here are more than academic. Keeping quantum systems cold is a major technical and financial burden. If we can design systems that tolerate, or even utilise, warmer starting conditions, we open the door to more practical, scalable quantum technologies.

Ian Yang, who led much of the experimental work, noted that they were able to generate “highly mixed quantum states with distinct quantum properties,” which is typically difficult to achieve. That could help researchers build better nanomechanical oscillators—devices that are especially hard to cool without compromising their quantum functionality.

As Oriol Romero-Isart, one of the theorists involved, put it: “This opens up new opportunities for the creation and use of quantum superpositions, particularly in systems where reaching the cold ground state is technically challenging.”

The results also open up new questions about how temperature affects other aspects of quantum behaviour beyond coherence. As experimental methods improve, the line between thermal and quantum systems might prove more flexible than expected, shaped as much by control and setup as by temperature alone.