The inverse Mpemba effect has been observed in a quantum bit (qubit). The research was done at the Weizmann Institute in Israel and suggests that under certain conditions a cooler trapped-ion qubit may heat up faster than a similar warmer qubit. The observation could have important implications for quantum computing because many leading qubit types must be maintained at cryogenic temperatures.

The Mpemba effect is the puzzling observation that hot water sometimes freezes faster than cold water. It was first recorded in antiquity and is named after Erasto Mpemba, who as teenager in Tanzania in 1960s sought an explanation for the effect – which he first encountered while making ice cream and then confirmed in a series of experiments. Despite the best efforts of physicists over the past six decades, the effect remains poorly understood.

Researchers have also observed the inverse Mpemba effect whereby a cold system heats up faster than a warm system. Theoretical and experimental studies have revealed a range of systems – magnetic, granular, quantum and more – that exhibit Mpemba effects.

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