Posted in | Quantum Physics

Ultrafast Quantum Simulations Help Study Dynamics of Electron-Ion Interactions

In the blink of an eye, an infinite number of very small interactions take place between thousands of particles in each piece of matter. However, replicating these tiny interactions in their complete dynamics was believed to be elusive.

Now, researchers from the University of Warwick and the University of Oxford have performed a new study that makes such simulations possible.

Thus, the researchers have provided a deeper understanding of the intricate mutual interactions that occur between the particles in adverse environments, for example, at the core of massive planets or even laser nuclear fusions.

At Warwick and Oxford, scientists have devised a novel method to replicate many-particle quantum systems, thus making it possible to study the dynamic characteristics of quantum systems that are fully attached to gradually moving ions.

The researchers have effectively and rapidly simulated the quantum electrons such that it can run for a very long time without any limitations. The impact of the electrons’ motion on the movement of the slowly moving ions can also be seen.

The study, which has been reported in the Science Advances journal, is based on a historically known alternative formulation of quantum mechanics—Bohm dynamics. The researchers have currently empowered Bohm mechanics to help study the dynamics of massive quantum systems.

Numerous quantum phenomena have been investigated for single or only a few interacting particles because huge complex quantum systems tend to overpower researchers’ computational and theoretical capabilities to make predictions. This is further complicated by the huge variation in timescale of the activity of diverse particle species—ions have larger mass and hence they evolve thousands of times slower when compared to electrons.

In order to resolve this issue, ions and electrons are decoupled in a majority of the techniques, and the dynamics of their interactions are also ignored; however, this considerably restricts one’s understanding of quantum dynamics.

Hence, to create a technique that enables researchers to account for the entire interactions between the electrons and ions, the scientists revived a traditional alternative formulation of quantum mechanics that was created by David Bohm. In the field of quantum mechanics, the wave function of a particle should be known.

It turned out that elucidating the wave function by a phase and the mean trajectory, as done by Bohm, is extremely useful. But it took an extra suit of approximations, as well as a number of tests, to expedite the calculations as dramatic as needed.

The latest techniques have certainly demonstrated an increased speed by over a factor of 10,000 (that is, four orders of magnitude) but are still consistent with earlier computations made for the static characteristics of quantum systems.

The novel method was subsequently used on a simulation of warm dense matter—a state between hot plasmas and solids, known for its intrinsic coupling of all types of particles and the requirement for a quantum description. In systems like those, the electrons as well as the ions can exhibit excitations in the form of waves, and both waves will affect one another.

The latest technique in this study can demonstrate its strength and can establish the impact of the quantum electrons on the waves of the traditional ions, whereas the static characteristics were shown to correlate with the earlier data.

At the heart of the various scientific problems are many-body quantum systems. These systems range from the complex biochemistry in human bodies to the behavior of matter within massive planets or even technological difficulties such as fusion energy or high-temperature superconductivity that reveals the potential range of applications of the latest method.

Bohm quantum mechanics has often been treated with skepticism and controversy. In its original formulation, however, this is just a different reformulation of quantum mechanics. The advantage in employing this formalism is that different approximations become simpler to implement and this can increase the speed and accuracy of simulations involving many-body systems.

Gianluca Gregori, Study Lead and Professor, University of Oxford

Dr Dirk Gericke from the University of Warwick, who helped in designing the novel computer code, stated that, With this huge increase of numerical efficiency, it is now possible to follow the full dynamics of fully interacting electron-ion systems.”

Gericke continued, “This new approach thus opens new classes of problems for efficient solutions, in particular, where either the system is evolving or where the quantum dynamics of the electrons has a significant effect on the heavier ions or the entire system.”

This new numerical tool will be a great asset when designing and interpreting experiments on warm dense matter. From its results, and especially when combined with designated experiments, we can learn much about matter in large planets and for laser fusion research. However, I believe its true strength lies in its universality and possible applications in quantum chemistry or strongly driven solids.

Dr Dirk Gericke, University of Warwick

Source: https://warwick.ac.uk/

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