Conventional computers use bits of information, binary digits. The quantum computer will use qubits, quantum bits. Now, researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw, have demonstrated that the chemical bit, the chit, can be formed from three touching droplets undergoing strictly defined oscillatory chemical reactions.

Konrad Gizynski and Jerzy Gorecki have demonstrated working memory in such a system based on the well-known Belousov-Zhabotinsky (BZ) oscillating reaction. In their system, the team added ruthenium as well as the standard ferroin catalyst in the BZ reaction. This additional catalyst makes the system photosensitive so that shining a blue light on it halts the oscillation.

"Our idea for the chemical storage of information was simple," explains Gorecki. "From our previous experiments we knew that when BZ droplets are in contact, chemical fronts can propagate from droplet to droplet. So we decided to look for the smallest droplet systems in which excitations could take place in several ways, with at least two being stable. We could then assign one sequence of excitations a logic value of 0, the other 1, and in order to switch between them, that is, to force a particular change of memory state, we could use light."

The team's proof of principle involved pipetting the requisite three droplets into decane and positioning the system above the ends of optical fibers. The droplets form a triangle so that each droplet touches its two neighbors and oscillatory chemical fronts can propagate through this arrangement in different ways. They were after a reversible "1-2-3" sequence that would give them two states to represent a "1" and a "0" in binary. Moreover, a circular sequence like this would resemble a spiral wave and so be more stable than back and forth oscillations. The team then showed that correctly selecting the time and length of illumination of appropriate droplets, they could change the direction of rotation 1-2-3 to 3-2-1, giving them control over the binary state. [Gizynski and Gorecki, Phys Chem Chem Phys (2017): DOI: 10.1039/c6cp07492h]

"In fact, our chemical bit has a slightly greater potential than the classical bit. The rotational modes we used to record states 0 and 1 had the shortest oscillation periods of 18.7 and 19.5 seconds, respectively. So if the system oscillated any slower, we could talk about an additional third logic state," adds Gizynski. The third state in this case could be used as a check digit. The research itself is of a fundamental nature at this stage, of course, we are probably some time away before a true chemical computer using chits becomes a reality.

"We have [also] published a numerical paper on BZ-droplets based classifiers where light is used to implement a classification function into a system composed of 25 interacting BZ droplets," Gizynski told Materials Today. "Now, we're working on building such a classifier in experimental system."

Figure: Three droplets with circulating chemical fronts can store information. The first chemical bit has been demonstrated by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. (Image credit: IPC PAS, Grzegorz Krzyzewski)

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".