Extracting entropy information from quantum dots
Blinking dots Photoluminescence image of individual quantum dots used in the experiment. Under time-dependent driving, the system is driven out-of-equilibrium and their blinking trajectories are modulated. (Courtesy: A Lindenberg) "> Blinking dots Photoluminescence image of individual quantum dots used in the experiment. Under time-dependent driving, the system is driven out-of-equilibrium and their blinking trajectories are modulated. (Courtesy: A Lindenberg) Researchers have succeeded in measuring how energy dissipates in quantum dots by quantifying the entropy they produce. The work, by a team at Stanford University in the US, could help in the optimization of real-world nanoscale devices used in applications such as quantum memories and information processing. Technologies like memory storage devices and information processors are intrinsically dissipative, explains materials scientist and engineer Aaron Lindenberg, who led this new study. Energy is lost as heat in many ways but at a fundamental level, this arises from the Landauer principle, which defines a lower limit for these energy costs. “When physical or computational processes evolve non-quasi-statically – for example, over a finite amount of time and out-of-equilibrium, the energy costs increase. Despite its fundamental and practical importance, directly measuring this dissipation remains extremely challenging, particularly as modern devices continue to shrink in size.” In the new work, Lindenberg and colleagues wanted to measure energy dissipation directly in real materials in contrast to previous experiments that measured entropy production in very clean systems, such as defect centres in diamond. “Previously studied materials behaved like simple two-state ‘Markov’ systems, where the probability of moving to the next step is determined only by the current state,” explains Lindenberg, “but real materials often have memory effects and hidden internal states. Good test systems Quantum dots, which are tin
