Scientists have detected a rare quantum phenomenon, predicted over 50 years ago, that creates a new state of matter with potential impacts on quantum computing.
Known as a superradiant phase transition (SRPT), this phase occurs when two separate groups of quantum particles start to oscillate in a synchronized, collective manner, according to a study published April 4 in Science Advances.
The particles involved were iron and erbium ions within a crystal. By cooling the crystal, composed of erbium, iron, and oxygen, to -457 °F (-271.67 °C) and applying a magnetic field 100,000 times stronger than Earth’s, researchers triggered the phenomenon.
At these extreme conditions, the team observed clear signs of an SRPT in the crystal, aligning perfectly with predictions from Robert H. Dicke’s 1954 model. The Dicke model first described superradiance—where excited atoms emit light faster than typical atoms—and set the stage for understanding SRPT as a unique state of matter driven by intense light-matter interactions. This was later expanded by Klaus Hepp and Elliot H. Lieb in 1973, who confirmed the phase transition’s existence.
“Originally, the SRPT was proposed as arising from interactions between quantum vacuum fluctuations — quantum light fields naturally existing even in completely empty space — and matter fluctuations,” said co-lead author Dasom Kim, a doctoral student in applied physics at Rice University, in a statement. “However, in our work, we realized this transition by coupling two distinct magnetic subsystems — the spin fluctuations of iron ions and of erbium ions within the crystal.”
Spin refers to a particle’s angular momentum, influencing its behavior in magnetic fields and the statistical properties of particle groups, which shape matter and fundamental forces. When thermal fluctuations, alternating magnetic fields, or other excitations cause a wave-like disturbance in a material’s spin pattern, it’s termed a magnon.
Previously, SRPT was considered impossible due to a fundamental limit in light-based systems. However, the team overcame this by creating a magnonic version of SRPT, with iron ions’ magnons replacing vacuum fluctuations and erbium ions’ spins acting as matter fluctuations.
The researchers observed one spin mode’s energy signal vanishing and a shift in the other, confirming SRPT’s presence.
“We established an ultrastrong coupling between these two spin systems and successfully observed a SRPT, overcoming previous experimental constraints,” Kim said.
SRPT’s unique properties could significantly advance quantum technologies through quantum squeezing, where fluctuations in one quantum property are reduced below the standard limit, though increased in another.
“Near the quantum critical point of this transition, the system naturally stabilizes quantum-squeezed states — where quantum noise is drastically reduced — greatly enhancing measurement precision,” Kim said in the statement. “Overall, this insight could revolutionize quantum sensors and computing technologies, significantly advancing their fidelity, sensitivity and performance.”
Beyond improving quantum measurement and computation precision, SRPT’s stabilization of quantum-squeezed states offers additional benefits. As SRPT stems from the collective behavior of many quantum particles, it could protect against individual qubit errors and decoherence—key challenges in quantum computing. This synchronized behavior may enable more stable qubits with longer coherence times and potentially faster quantum gates, the core components of quantum algorithms.
