@Nature Communications: Reversion of heat flow using quantum correlations

Irreversibility is a longstanding puzzle in physics. While microscopic laws of motion are invariant under time reversal, all macroscopic phenomena have a preferred direction in time. Heat, for instance, spontaneously flows from hot to cold. Eddington has called this asymmetry the arrow of time. At the phenomenological level, the second law of thermodynamics allows one to predict which processes are possible in nature: only those with non-negative mean entropy production do occur. A microscopic resolution of the apparent paradox of irreversibility was put forward by Boltzmann, when he noted that initial conditions break the time-reversal symmetry of the otherwise reversible dynamics. In addition to breaking time reversal, initial conditions also determine the arrow’s direction. The observation of the average positivity of the entropy production in nature is often explained by the low entropy value of the initial state. This opens the possibility to control or even reverse the arrow of time depending on the initial conditions.

In standard thermodynamics, systems are assumed to be uncorrelated before thermal contact. As a result, according to the second law heat will flow from the hot to the cold body. However, it has been theoretically suggested that for quantum correlated local thermal states, heat might flow from the cold to the hot system, thus effectively reversing the arrow’s direction.

We report the experimental demonstration of the reversal of heat flow for two initially quantum correlated qubits (two spin-1/2 systems) prepared in local thermal states at different effective temperatures employing Nuclear Magnetic Resonance (NMR) techniques.

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Investigacion y Ciencia: Las correlaciones cuánticas invierten la flecha termodinámica del tiempo.

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Ifuun (Chinese science portal): 逆轉「時間之箭」的量子實驗.

SCIENCEmag cz (Czech science portal): Teplo proudí ze studeného objektu na horký.

Europa Press: El concepto de que el tiempo discurre en dirección única es relativo.

Inovação Tecnologica: Experimento faz tempo andar para trás.

The Daily Express: Scientists manage to ‘REVERSE the arrow of time’ in astonishing study.

The Inquisitr: Physicists demonstrate that time can actually travel in a reverse direction under the right conditions.

Science alert: Physicists Have Created a Set of Conditions in Which Time Seems to Run in Reverse.

Portal Terra: Experimento mostra que o tempo pode não "andar" somente para frente. Futurism: Physicists have created a set of conditions in which time seems to run in reverse. Futurism Diario ABC (Spanish newspaper): Logran, por primera vez, que el tiempo fluya hacia atrás. Dialectica (Romanian news portal): Fizică: Un nou experiment inversează „săgeata timpului”. UP'Magazine (French innovation news): Des scientifiques ont découvert que le temps pouvait s’écouler à l’envers.