Cold-Atom Experiment Tests Internal Time Definition Based on Entropy in Quantum System
@NewScientist reported that researchers cooled 20,000 rubidium atoms and used quantum exchanges to generate an internal time based on increasing entropy. The calculated states matched experimental results when the internal time was inserted into the Schrödinger equation.
New ScientistGiovanni Barontini at the University of Birmingham cooled approximately 20,000 rubidium atoms to temperatures close to absolute zero using lasers and electromagnetic forces. He divided the atoms into two sectors labelled “bright” and “dark”. Lasers then induced quantum-level interactions by causing atoms to exchange between the sectors.
The exchanges changed the entropy of the toy universe. Barontini defined an internal time based on the direction of increasing entropy. He inserted this internal time into the Schrödinger equation to calculate the atoms’ quantum states, and the calculated states matched the experimental results.
Nevill Mott first proposed in the 1930s that time arises from quantum correlations. In 2013, Marco Genovese and colleagues at the National Metrology Institute of Italy performed an experiment with entangled photons that demonstrated time emerging from quantum correlations. The cold-atom experiment is more complex than the 2013 entangled-photon experiment.
Marco Genovese stated that the cold-atom experiment succeeded in making the Schrödinger equation work with the system’s internal time, which had not been done before. Claus Kiefer at the University of Cologne stated that the experiment connects to the problem of combining gravity and quantum theory.
Carlo Rovelli at Aix-Marseille University stated that the experiments are constructed based on already-understood physics and cannot discover something new about time.
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