University of Birmingham physicist shows time may emerge from quantum system
University of Birmingham Physicists Build 24,000-Atom Quantum System Without External Clocks
Time may not be a fundamental ingredient of reality and can instead emerge from the internal changes and relationships of a quantum system, according to experimental findings published in Physical Review Research. Professor Giovanni Barontini at the University of Birmingham demonstrated this phenomenon by creating a miniature universe using 24,000 atoms cooled to temperatures barely above absolute zero, observing how a consistent progression of time can be tracked without relying on an external clock.
The Tech TL;DR:
- Researchers created a miniature quantum model using 24,000 ultracold atoms to test theories of time in quantum gravity.
- By tracking changes in entropy and particle distribution across isolated regions, the system measured time internally without an external clock.
- The experiments show that entropic time can establish an arrow of time and even validate foundational quantum equations like the Schrödinger equation.
Isolating Atoms and Simulating Cosmic Expansion in the Laboratory
To construct this miniature cosmos, Barontini isolated a cloud of approximately 24,000 atoms inside a controlled quantum architecture. At temperatures just a few billionths of a degree above absolute zero, quantum effects dominate the system’s behavior. Two laser beams operating at different frequencies established a thin barrier that divided the quantum cloud into two distinct areas: an observed bright region and an unobserved dark region. Atoms freely migrated across this barrier while the bright region was manipulated to undergo repeated cycles of expansion and contraction. These cycles served as simplified analogs to cosmological events, resembling the initial expansion of the Big Bang and the hypothetical inward collapse known as the Big Crunch.
Tracking Entropic Time Through Particle Distribution Changes
The core innovation of the experiment involved measuring time through entropy rather than standard chronological units like seconds or minutes. As atoms shifted between the bright and dark zones, the particle distribution within the bright region constantly altered. Barontini used these distributional shifts to define an internal measure of time termed “entropic time.” When the spread of the particle distribution increased or decreased, the system registered forward progression. When the distribution remained static, this internal measure of time effectively halted. The experiment established that entropic time moves consistently in a single direction to create an arrow of time, and it scales dynamically by speeding up or slowing down depending on the rate of entropy change inside the quantum system.
Theoretical frameworks such as the Wheeler-DeWitt equation attempt to reconcile quantum mechanics with gravity by describing the universe as a single, unchanging quantum state lacking any built-in time variable. Barontini’s experiment provides empirical validation that a quantum system can possess a meaningful internal measure of time without depending on an external clock. Beyond simply ordering events sequentially, the research demonstrated that a version of the Schrödinger equation can be expressed using entropic time.
# Conceptual Model of Entropic Time Progression in Ultracold Atoms
def calculate_entropic_time(particle_distribution_state_t1, particle_distribution_state_t2):
# Track changes in disorder and particle spread between observed regions
delta_entropy = compute_shannon_entropy(particle_distribution_state_t2) - compute_shannon_entropy(particle_distribution_state_t1)
if delta_entropy != 0:
return "Time Advances: Arrow Established"
else:
return "Progression Halts: Zero Net Change"
Future Directions for Quantum Cosmology Research
The findings offer a concrete platform to investigate complex theoretical problems in quantum cosmology without relying on external temporal references. Future iterations of the experiment intend to scale the complexity of the quantum systems to model early universe dynamics, black hole mechanics, and competing theories of temporal emergence. Barontini noted that this approach provides a reliable method to describe dynamics in frameworks where time is omitted as a fundamental feature.
“This study provides the first controlled experimental evidence that ‘time’ can be defined by changes within a system rather than as the external ‘ticking clock’ we think of as time,” Professor Giovanni Barontini stated.