An article by the Quantum Systems team published in Nature Communications

The article by the Quantum Systems team entitled 'Observation of quantum criticality of a four-dimensional phase transition' by Farid Madani, Maxime Denis, Pascal Szriftgiser, Jean-Claude Garreau, Adam Rançon, and Radu Chicireanu has been published in the journal Nature Communications.

Abstract :

Phase transitions are ubiquitous in physics, ranging from thermal phenomena like the boiling of water to magnetic transitions in solids. They also encompass cosmological phase transitions that occurred in the early universe, as well as the transition to a quark-gluon plasma in high-energy collisions. Quantum phase transitions, which are particularly fascinating, occur at temperatures close to absolute zero and are driven by quantum fluctuations rather than thermal ones. The intensity of these fluctuations is highly sensitive to the dimensionality of physical systems, which determines the existence and nature of phase transitions. Low-dimensional systems often exhibit suppression of phase transitions, while high-dimensional systems tend to follow simpler, mean- field-like behavior.

Among quantum phase transitions, the Anderson localization-delocalization transition stands out, as it is one of the rare examples believed to retain its non-trivial (non-mean-field) character in all
dimensions (d ≥ 3). This work presents the first observation and precise characterization of the Anderson transition in dimension d=4 – experimentally realized using ultracold atoms as a quantum simulator with synthetic dimensions.

By submitting the atomic gas to a quasi-periodic excitation to simulate both disorder and synthetic dimensions, we experimentally observe and study a phase transition between (dynamically) localized and delocalized phases. Our results reveal several fundamental features that define the specifically four-dimensional nature of the observed phase transition: the scale invariance at criticality for d=4, the agreement between the measured critical exponents and numerical predictions for the 4D Anderson transition, and an excellent agreement with Wegner’s scaling law, which relates these exponents to the system’s dimensionality.

Our study constitutes the first experimental demonstration of the non-mean-field nature of the Anderson transition in four dimensions. These results open a new paradigm for the experimental exploration of complex critical phenomena – and more generally of physical theories – in higher dimensions.

The full article can be found here: https://rdcu.be/eeYzG