Researchers have created a model universe using approximately 20,000 rubidium atoms cooled to near absolute zero, demonstrating how time itself may emerge from quantum interactions rather than being a fundamental aspect of reality. The experiment divided this ultracold system into “bright” and “dark” sectors, intentionally mirroring the concept of dark matter, before using lasers to induce interaction and observe a change in entropy, a key indicator of time’s passage. “He was building his own small universe, and I was thinking that that’s pretty much what we do also in our labs, when we build an ultracold-atoms system,” explains Giovanni Barontini at the University of Birmingham, reflecting on the inspiration for the work. “The present work further elaborates on this idea with some significant progress,” says Marco Genovese at the National Metrology Institute of Italy. By defining an internal time within this system and successfully applying it to the Schrödinger equation, the team found experimental results aligned with theoretical predictions, building on earlier work with entangled light particles and offering new insight into the nature of time at a quantum level.
Ultracold Rubidium Atoms Model a “Toy Universe”
A meticulously crafted model universe comprised of 20,000 rubidium atoms has allowed physicists to model the emergence of time itself, suggesting it may not be a fundamental constant but rather an illusion arising from quantum interactions. The system, cooled to temperatures approaching absolute zero using lasers and electromagnetic forces, was initially divided into two distinct sectors, labeled “bright” and “dark,” a deliberate parallel to the concept of dark matter within our own cosmos. This initial state represented a timeless, unchanging environment, but the introduction of interaction between the sectors via laser manipulation fundamentally altered the system’s entropy. Researchers observed that as atoms exchanged between the “bright” and “dark” regions, a measurable change in disorder occurred, mirroring the established link between entropy and the flow of time in our universe.
Barontini’s team then successfully integrated this internally defined time into the Schrödinger equation, accurately predicting the quantum states of the atoms, a feat previously unachieved in similar models. Marco Genovese at the National Metrology Institute of Italy says that the present work further elaborates on this idea with significant progress, noting the increased complexity of the cold-atom universe compared to previous experiments utilizing entangled photons. This approach builds on earlier work suggesting time arises from quantum correlations, first proposed by Nevill Mott in the 1930s, and recently demonstrated with entangled light particles.
“But it isn’t a confirmation that this is how time actually works at all scales,”
Quantum Interactions Define Internal Time
Giovanni Barontini initiated the experiment while observing his son’s play, noting the parallel between building a miniature universe and creating ultracold-atom systems. He posited that a static system lacks the passage of time, prompting the investigation into whether interaction could generate a sense of temporal flow. To model this, Barontini and his team cooled approximately 20,000 rubidium atoms to near absolute zero, constructing a model universe divided into “bright” and “dark” sectors, a deliberate analogy to dark matter. Initially unchanging, this system became dynamic when lasers induced interaction between the sectors, altering the model universe’s entropy. This change is crucial, as increasing entropy is directly linked to the flow of time in our own universe; Barontini was then able to define an internal time for the model universe. Marco Genovese at the National Metrology Institute of Italy acknowledges the significance of this advancement, stating that the present work further elaborates on this idea with some significant progress. While acknowledging the limitations of the model, Barontini believes the study confirms long-held ideas and opens avenues for further exploration, potentially even simulating black hole-like conditions within the ultracold miniverse.
“He was building his own small universe, and I was thinking that that’s pretty much what we do also in our labs, when we build an ultracold-atoms system,”
Crucially, the introduction of interaction between these sectors, achieved through precisely calibrated lasers, instigated a measurable change in entropy, providing a physical basis for the flow of time within the model. While acknowledging the limitations of this model universe compared to the complexities of the cosmos, Barontini believes this work offers experimental validation of long-held theoretical concepts and opens avenues for exploring the relationship between quantum gravity and the fundamental nature of time itself.
