A new dissipation-based method to probe quantum correlations

Quantum systems are known to be prone to dissipation, a process that entails the irreversible loss of energy and that is typically linked to decoherence. Decoherence, or the loss of coherence, occurs when interactions between a quantum system and its environment cause a loss of coherence, which is ultimately what allows quantum systems to exist in a superposition of states.

While dissipation is generally viewed as a source of decoherence in quantum systems, researchers at Tsinghua University recently showed that it could also be leveraged to study strongly correlated quantum matter.

Their paper, published in Nature Physics, introduces a new method to probe intrinsic quantum many-body correlations and demonstrates its potential for studying the dissipative dynamics in strongly correlated one-dimensional (1D) quantum gases.

“Our work was inspired by the emerging fields of open quantum systems and non-Hermitian physics,” Yajuan Zhao, first author of the paper, told Phys.org. “Instead of viewing dissipation as a source of decoherence, we sought to use it as a tool to reveal intrinsic quantum many-body correlations.”

As part of their recent study, Zhao and her colleagues wanted to devise an entirely new strategy to detect intrinsic correlated features in strongly correlated quantum systems, such as 1D quantum gases, leveraging dissipation effects (i.e., reaching beyond conventional quantum mechanics methods based on Hermitian operators).

To demonstrate their proposed approach, they first prepared 1D Bose gases using ultracold Rb-87 atoms, which were trapped in a 1D array of tubes within a 2D optical lattice.

“By shining near-resonant dissipation light onto the gases, we induced a controlled one-body loss and monitored the atom number decay via absorption imaging,” explained Zhao.

“Instead of a simple exponential decay, we observed a stretched-exponential decay, where the stretched exponent is a universal property, only determined by the dimensionless interaction strength, independent of the characteristics of the dissipative probe, and robust against thermal effects. Specifically, the exponent measures the anomalous dimension of Luttinger liquid.”

The researchers used light to control dissipation in the 1D quantum gases. They found that this allowed them to probe quantum correlations in these systems. Overall, their findings demonstrate that dissipation can also be leveraged, enabling the collection of measurements that would be difficult to attain employing other existing approaches for studying quantum many-body correlations.

“The most notable finding is that the atom number decay under well-controlled one-body loss follows a universal stretched-exponential law, with the stretched exponent related to the anomalous dimension of the spectral function, which is challenging to be measured in closed systems,” said Zhao.

This recent study by Zhao and her colleagues could soon open new possibilities for the study of strongly correlated quantum many-body systems and quantum materials. In the future, the methods employed by the researchers could help to better understand these strongly correlated systems, which could in turn also inform the development of new quantum technologies.

“Our experiment provides a novel and experimentally accessible way to probe quantum correlations, verify the validity of utilizing dissipation as a probe, and thus extends the conventional linear response theory from closed systems to open systems,” added Zhao.

“In our next studies, we plan to utilize this dissipative probe to explore other quantum many-body phenomena, such as spin-charge separation and non-Fermi liquid behavior in high-temperature superconductors.”

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