Reviewed by Lexie CornerSep 3 2024
A group headed by Robert Keil and Tommaso Faleo from the Department of Experimental Physics has examined the relationship between entanglement and interference in quantum systems involving more than two particles. Their findings were published in the journal Science Advances.
Tommaso Faleo in the laboratory at the Department of Experimental Physics. Image Credit: University of Innsbruck
Collaborating with scientists from Heriot-Watt University in the United Kingdom and the University of Freiburg in Germany, the team led by Robert Keil and Tommaso Faleo gained new insights into the behavior of multi-particle quantum systems. In an interview, Tommaso Faleo explained how interference patterns involving more than two photons can be understood. Here is a summary:
The study aimed to investigate and better understand the connection between interference and entanglement in systems with more than two particles. In such multi-particle systems, interference dynamics are particularly complex, and the presence of entanglement adds an additional layer of intricacy. The researchers focused on examining the specific properties of interference patterns that emerge when some particles are in an entangled state.
Entanglement is a quantum phenomenon where the properties of two or more particles become so interconnected that they can no longer be described as independent entities, regardless of the distance between them. This concept is foundational to several quantum technology applications.
In classical physics, waves can create interference patterns when their amplitudes combine constructively (increasing the overall effect) or destructively (canceling each other out). Similarly, in quantum physics, interference occurs when the probability amplitudes of different quantum states combine, either increasing or decreasing the likelihood of certain events.
Two-particle interference introduces an additional layer to quantum interference, arising from the indistinguishability of identical particles. Hong, Ou, and Mandel first demonstrated this phenomenon in 1987, and it has since become the cornerstone of many optical quantum technologies. Multi-photon interference expands this effect to systems involving more than two particles.
The researchers found that in systems with more than two particles, interference patterns become significantly more complex than in simpler systems, such as those demonstrated in the original Hong-Ou-Mandel experiment. These patterns are influenced not only by the quantum states of individual particles but also by the entanglement between them.
In the interference scenario, the particles’ entanglement bridges the spatial gap between separate interferometers, resulting in an interference pattern that is determined by the overall quantum state of all particles involved and is inaccessible when one or more particles are removed from the dynamics.
These findings offer new insights into the behavior of multi-particle quantum systems and how their quantum states influence interference patterns. The study describes a novel type of collective interference effect that combines entanglement with the complex dynamics of multi-particle systems, advancing our understanding of quantum mechanics in many-body systems. This could potentially lead to new theoretical discoveries and breakthroughs in quantum technology.
Journal Reference:
Faleo, T., et. al. (2024) Entanglement-induced collective many-body interference. Science Advances. doi.org/10.1126/sciadv.adp9030