Scientists produce ‘Hot Schrödinger Cat States’

The principle of quantum superposition allows us to prepare a system for overlapping two arbitrary states. The paradigmatic example is the overlapping of two consistent conditions. The overlapping of such states is typically called a Schrödinger Cat State, while Erwin Schrödinger’s original thought experiment is prepared for overlapping the two mixed situations dominated by cat-body temperature and an out-of-balance system-classical fluctuations. Physicists at the University of Innsbruck managed to create hot Schrödinger cat states in a superconducting microwave resonator.

Schrödinger cat situations are a fascinating phenomenon in quantum physics, where the quantum object is located at the same time in two different cases.

In Erwin Schrödinger’s thought experiment, he is also a living and dead cat.

In actual experiments, such synonymity has been seen in the locations of atoms and molecules and in the release of electromagnetic resonators.

Previously, these analogs for Schrödinger’s thought attempt were first created by cooling the quantum object to the ground state, with the lowest possible energy.

In a new study, Dr. Gerhard Kirchmauir and his colleagues at the University of Innsbruck showed that it was really possible to create quantum superpositions from thermal excited states.

“Schrödinger also assumed that it was a ‘warm’ cat in his thought experiment,” he said.

“We wanted to know whether these quantum effects can be produced if we don’t start with the ‘cold’ floor state.”

To create Schrödinger cat situations, the researchers used a transmoner in the microwave resonator.

They managed to create quantum superpositions at temperatures up to 1.8 k, which is sixty times warmer than the ambient temperature in the space.

The first author of the study. “Our results show that it is possible to produce quite mixed quantum situations with different quantum characteristics,” Ian Yang said.

Scientists used two special protocols to form hot Schrödinger cat states.

These protocols have previously been used to produce cat situations starting from the ground condition of the system.

“Adapted protocols also work at higher temperatures and produce different quantum parasites, Professor Oriol Romero-Isart, the columnist of the study.

“This opens new opportunities for the creation and use of quantum superpositions in nanomechanical oscillators, for which it can be technically difficult to achieve the ground.”

Thomas Most of our colleagues were surprised when we first mentioned our results, because we usually think of temperature as something that destroys quantum effects, ”he said.

“Our measurements confirm that quantum parasite can continue even at high temperature”.

Findings can benefit the development of quantum technologies.

“Our work reveals that it is possible to observe and use quantum phenomena even in less ideal, warmer environments, Kir Kirchmair said.

“If we can create the necessary interactions in a system, the temperature is not important.”

A paper Findings published in the magazine Science progress.

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Ian Yang et al.. 2025. Hot Schrödinger Cat States. Science progress 11 (14); doi: 10.1126/sciadv.adr4492