Level schemes constructed for an effective two-level system in contact with two heat baths in the trapped 40Ca+ ion. (a) Levels constructed for the dissipative channels regarding cold heat bath. (b) Levels constructed for the dissipative channels regarding hot heat bath. Each dissipative channel is constructed by two heterochromatic lasers with the wavelengths of 729 and 854 nm, respectively, where the Rabi frequency Ωn1 (Ωn2), with n=1, 2, 3, and 4, represents the resonant coupling of a sublevel of the ground state (metastable state) to a sublevel of the metastable state (excited state), and the decay of the excited state to the ground state accomplishes the effective procedure of the dissipative channel. Here, we set Ωn2≫Ωn1 to guarantee the steady dissipative process, and the lifetime of the excited state is 6.9 ns; i.e., the decay rate Γ/2π=23.1MHz, while the metastable state has a negligible decay rate due to 1.2 s lifetime. Credit: DOI: 10.1103/PhysRevLett.128.050603
A team of researchers affiliated with multiple institutions in China has verified the relationship between the rate at which a nonequilibrium process happens and the rate at which it creates entropy. In their paper published in the journal Physical Review Letters, the researchers describe experiments with individual calcium atoms in an ion trap and findings about the relationship between their lifespan and the rate at which they are able to exchange energy using different types of baths.
Two years ago, physicists Massimiliano Esposito and Gianmaria Falasco used a statistical mathematical outline to show that there exists a relationship between the lifetime of a nonequilibrium process and the rate of entropy involved with the process. In this new effort, the researchers tested the ideas described in the work by Esposito and Falasco using trapped calcium ions.
In their experiments, the team in China used light to stimulate calcium atoms in a trap and measured the changes in the rate of entropy—in this case, that involved measuring the rate of change as the system moved from one electronic state to another. The changes in electronic states do not come smoothly, however; instead, they come in jumps and occur at random times. The researchers also note that quantum jump theory posits that such jumps are ruled by the dissipation of energy between a given system and its environment.
To measure the jumps, the researchers used multiple lasers to create artificial environments for the trapped ions, which they describe as heat baths. Notably, they also used separate lasers to excite electronic states in the ion that were not part of quantum jumps. The researchers then manipulated the lasers to control the transitions, one of which behaved as a "cold bath" the other as a "hot bath." The result was a model of the system described by Esposito and Falasco.
They suggest their work could help researchers working on quantum computers by showing how dissipation in such systems is working. They also note that their work could also apply equally well to classical devices.
More information: L.-L. Yan et al, Experimental Verification of Dissipation-Time Uncertainty Relation, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.050603
Journal information: Physical Review Letters
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