Modelling chemical reactions using semiconductor quantum dots

We propose the use of semiconductor quantum dots for simulating chemical reactions, as electrons are redistributed among such artificial atoms. We show that it is possible to achieve various reaction regimes and obtain different reaction products by varying the speed of voltage changes applied to the gates forming quantum dots. Considering the simplest possible reaction, H2 +H→H+H2, we show how the necessary initial state can be obtained and what voltage pulses should be applied to achieve a desirable final product. Our calculations have been performed using the Pechukas gas approach, which can be extended for more complicated reactions. Copyright c © EPLA, 2007 Detailed simulations of chemical and biological processes can provide crucial insight on these and help determining optimal experimental regimes and conditions. However, the high-accuracy modelling, at the quantum level, of even the simplest chemical reactions represents a significant challenge because it encompasses changes that involve the motion of electrons in the forming and breaking of chemical bonds. On classical computers, the resource requirements for the complete simulation of the time-dependent Schrödinger equation scale exponentially with the number of atoms in a molecule, imposing very severe limitations in the systems that can be modelled. However, recent developments of novel quantum computation schemes allow a polynomial scale of required resources. Via these approaches, a quantum system can simulate the behavior of another quantum system of interest (see, e.g., [1–3]). Semiconductor quantum dots can be described as artificial atoms (see, e.g., [4]). These have discrete electron spectra revealing a shell structure and exchange corrections to the electron energies according to Hund’s rules. In this sense, coupled quantum dots can be regarded as artificial molecules [5]. Depending on the tunnel coupling strengths, electron distribution, and shell structure, the dots can form both ionicand covalent-like bonds. Manifestations of these molecular states in double-dot structures were observed by numerous groups [6]. The idea of using the charge degrees of freedom in double-dot systems as a qubit has been proposed theoretically [7] and implemented experimentally [8]. Recent achievements in nanotechnology facilitate the precise control of the number of electrons in quantum dots and the tunnel energy splittings, by tuning the voltages applied to the gates [9]. Measuring the current through a quantum point contact in the vicinity of the structure allows the determination of the exact charge locations [10]. Moreover, structures with three coupled quantum dots have been recently fabricated and characterized [11,12] with the potential to easily increase the number of dots, as needed. Based on these developments, we propose to employ the electron redistribution in coupled quantum dot systems for chemical reaction modelling. The number of electrons in the first and second quantum dot shells are 2 and 4, respectively. Accordingly, a quantum dot with one electron can be considered as an artificial hydrogen atom