Quantum criticality at infinite temperature

TL;DR

This paper demonstrates that quantum criticality, typically observed at low temperatures, can be detected at infinite temperature using long-coherence quantum probes, revealing quantum fluctuations by removing thermal effects.

Contribution

It introduces a method to observe quantum criticality at infinite temperature using long-coherence probes and echo control to suppress thermal fluctuations.

Findings

Quantum criticality detectable at infinite temperature with long-coherence probes.

Echo control removes thermal fluctuations, revealing quantum effects.

Potential to study quantum orders at nano- or pico-Kelvin temperatures.

Abstract

Quantum criticality, being important as an indicator of new quantum matters emerging, is known to occur only at zero or low temperature. We find that a quantum probe, if its coherence time is long, can detect quantum criticality at infinitely high temperature. In particular, the echo control over a spin probe can remove the thermal fluctuation effects and hence reveals the quantum fluctuation effects. Probes with quantum coherence time of milliseconds or seconds can be used to study emerging quantum orders that would occur at extremely low temperatures of nano- or pico-Kelvin. This discovery establishes a physical link between time and inverse temperature and provides a new route to the wonderland of quantum matters.