The researchers investigated the Mpemba effect in quantum systems, a phenomenon in which hot water can freeze faster than cold water. This quantum Mpemba effect retains the memory of its initial conditions, which affects its thermal relaxation later. The team used two quantum dot systems and detected the Mpemba quantum thermal effect across different conditions, indicating potential broader applications beyond thermal analysis.
Hotter quantum systems can cool faster than their initially cooler counterparts.
Does hot water freeze faster than cold water? Perhaps Aristotle was the first to address this question, which later became known as Mpemba effect.
This phenomenon originally refers to Non-monotonic initial temperature dependence from the time of initiation of solidification, but have been observed in various systems – including colloids – and have also become known as the mysterious relaxation phenomenon that depends on initial conditions.
However, very few have previously studied this effect in quantum systems.
What is the Mpemba effect?
The Mpemba effect is a counterintuitive phenomenon where hot water can freeze faster than cold water under certain conditions. Named after Erasto Mpemba, a Tanzanian student who noticed this effect in the 1960s and later brought it to the attention of the scientific community, the phenomenon has been a subject of curiosity for centuries, with references dating back to the likes of Aristotle. The exact cause of the Mpemba effect is still a matter of debate among scholars.
recent results
Now, a team of researchers from Kyoto University and Tokyo University of Agriculture and Technology has shown that the quantum Mpemba effect of temperature can be achieved over a wide range of initial conditions.
“The quantum Mpemba effect bears the memory of initial conditions leading to anomalous thermal relaxation at later times,” explains project leader and co-author Hisao Hayakawa at the Yukawa Institute for Theoretical Physics in Kyoto.
Two quantum dot systems connected in a thermal bath, one in which current is flowing and the other in equilibrium. The temporal evolution towards a steady state was followed for each. Source: Kyoto Yu / Hisao Hayakawa
Hayakawa’s team set up two quantum dot systems connected to a thermal bath, one in which current was flowing and the other in equilibrium. Both were quenched to a hypothermic equilibrium state, allowing the team to follow the evolution of time toward a steady state with respect to the matrix of density, energy, entropy, and, most importantly, temperature.
Achieving the quantitative Mpemba effect
“When the two versions intersected before reaching the same equilibrium state—so that the hotter part becomes cooler and vice versa in an identity inversion—we knew we had achieved the thermal quantum Mpemba effect,” says co-author Satoshi Takada of TUAT. .
After analyzing The principal quantum equation“We also discovered that we obtained a quantum thermal Mpemba effect in a wide range of parameters, including reservoir temperatures and chemical potentials,” adds first author and reporter Amit Kumar Chatterjee, also from Kyoto.
“Our results encourage us to explore the potential use of the quantum Mpemba effect in future applications beyond thermal analyses,” says Hayakawa.
Reference: “Quantum Dot Mpemba Effect with Reservoirs” by Amit Kumar Chatterjee, Satoshi Takada and Hisao Hayakawa, August 22, 2023, Available here. Physical review letters.
doi: 10.1103/PhysRevLett.131.080402