University of Chicago scientists’ new method for quantum simulations could lead to breakthroughs

CHICAGO (CBS) — You may not hear the term “phase transition” in our daily weather forecasts very often, but it’s the driving process behind many meteorological terms and phenomena – from dew points and relative humidity to something as simple as rain turning to snow as the temperature drops.

You will not, however, hear about quantum phase transitions in daily weather forecasts. But quantum phase transitions were in the news Wednesday, because in the labs at the University of Chicago, some valuable research on how to simulate and study those far more complex phenomena more easily has been under way.

Quantum phase transitions are not observable in the same way as everyday phase transitions such as ice to liquid water, or liquid water to vapor. As explained by the U of C, quantum phase transitions happen when some materials are cooled to a temperature near absolute zero – the theoretical point at which there is no heat energy and atoms are not moving, or about -459.67 degrees Fahrenheit.

The U of C says quantum phase transitions can “make a physicist’s jaw drop.” They can involve a material becoming magnetic when it wasn’t before, or gaining a “superpower” in which it can conduct electricity without losing any energy as heat, the U of C said.

The math required to calculate quantum phase transitions is so complex that even supercomputers have a hard time with it, the U of C said. But a new study proposes a shortcut that pulls only the most important information into the mathematical equations and can create a map of all possible phase transitions in the system being studied, the U of C explained.

Researchers say the new study could go on to bring about technological breakthroughs, the U of C said.

As explained by the U of C, phase transitions such as evaporation and condensation are dependent on changes in the temperature. Quantum phase transitions, by contrast, are instead brought about by environmental interferences such as a magnetic field, the U of C said.

Quantum phase transitions occur as a consequence of many electrons acting in relationship with one another, the U of C said. To simulate such transitions, scientists must create models that acknowledge the possibilities of what could happen to each and every electron – and thus, running those simulations requires computing power that quickly runs out of control, the U of C said.

Complex and powerful quantum computers are believed to be better suited for such calculations, but still in that case, the result is reams of data that need to be translated back to the language of everyday computers to be understood by scientists, the U of C said.

Leibniz Computing Center in Garching
A cryostat from a quantum computer at the Leibniz Computing Center in Garching, Bavaria, Germany.

Sven Hoppe/picture alliance via Getty Images

U of C researchers sought out a way to simplify the calculations on quantum phase changes without any loss of accuracy. So instead of creating simulations that require calculating each and every variable for all the electrons in a quantum system, the researchers found a new approach in which they substituted a set of numbers describing the possible interactions between each pair of electrons, the U of C said.

This is known as a “two-electron reduced density matrix,” and allows researchers to map all the phases a quantum system can experience, the U of C said. Researchers said it turned out to be as accurate as the data-intensive method that involves predicting all the possibilities for every electron.

David Mazziotti, a theoretical chemist with the Department of Chemistry and the James Franck Institute at the U of C and a senior author for the study, told the U of C News Office’s Louise Lerner the new calculation method could be key for developing a greater understanding of quantum phase transitions.

“There are some areas that have been underexplored because they are so difficult to model,” Mazziotti was quoted. “I hope this approach can unlock some new doors.”

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