Quantum Coherence and Information Transfer: from Quantum Optics to Biomolecules

Dear Colleagues,

This Special Issue is a continuation of the Special Issue on “Quantum Information and Quantum Optics” that was successfully published in Entropy the past year.

Quantum information is a steadily growing field of investigation in virtue of our increasing capability to observe and describe exquisite quantum effects appearing in diverse systems ranging from atomic and atom-radiation systems to complex chemical and biophysical systems. In all these systems, quantum information is produced by quantum coherence and, more specifically, by the quantum correlations inherent in their short-time coherent evolution. Conversely, the same quantum information framework is used to describe such correlations and determine their value in terms of information production and transfer, with potential applications of technological relevance. In fact, different entropy measures have been developed over the years to characterize quantum-type correlations, including quantum conditional entropy, mutual entropy, (relative) entropy of entanglement, and the strictly related entanglement of formation.

Quantum coherence plays a crucial role in quantum optics and could be used to convey quantum information. All fundamental models in the field of quantum optics imply the coherent evolution of quantum systems on appropriately short timescales. In fact, many non-classical features in the physical behavior of confined matter–radiation are attributable to the coherence inherent in the dynamic evolution of the system. A role for quantum correlations is also expected when partial quantum coherence survives long enough during the evolution of composite quantum systems.

Similarly, quantum coherence is critically important in a myriad of chemical and biological processes. Tunneling of electrons and protons are emblematic cases of coherence effects in charge and energy transfer reactions. Nontrivial quantum coherence effects have been highlighted, in recent years, by the evolution of spectroscopic techniques, such as two-dimensional electronic spectroscopy. The application of such techniques has shown that, despite the disorder of chemical and biological systems, quantum correlations might survive long enough to influence their behavior. This observation has motivated the rapid growth of research that aims to use quantum coherence to enhance the function of biophysical systems. Within this framework, information theory concepts such as the relative entropy of entanglement have been used to characterize the possible presence of quantum entanglement in photosynthetic systems.

The classes of systems in which quantum coherence plays, or can play, an important functional role have been further and significantly increased by the advances in nanoscale physics and chemistry over the past few decades, with the exploration of a great variety of systems ranging from Josephson junctions to low-dimensional materials (for example, graphene or transition metal dichalcogenides), single-molecule junctions, molecules interacting with cavity quantum fields or with surface plasmons in confined space. Some of these systems have aroused renewed interest for the opportunities they offer to perform quantum information transfer and quantum computing.

We solicit contributions to this Special Issue of Entropy, with particular emphasis on the underlying role of quantum coherence in the abovementioned research areas, as well as on fruitful links among such areas.

Prof. Antonino Messina
Dr. Agostino Migliore
Guest Editors

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