Qubits, entangled states, and quantum gates realized on a set of classical pendulums

Here we show that the concepts behind such terms as entanglement, qubits, quantum gates, quantum error corrections, unitary time evolution etc., which are usually ascribed to quantum systems, can be adequately realized on a set of coupled classical pendulums.Comment: Supplementary Materials can be found in "Other Formats" -> sourc

Computation of the Spatial Distribution of Charge-Carrier Density in Disordered Media

The space- and temperature-dependent electron distribution n(r,T) determines optoelectronic properties of disordered semiconductors. It is a challenging task to get access to n(r,T) in random potentials, while avoiding the time-consuming numerical solution of the Schrödinger equation. We present several numerical techniques targeted to fulfill this task. For a degenerate system with Fermi statistics, a numerical approach based on a matrix inversion and one based on a system of linear equations are developed. For a non-degenerate system with Boltzmann statistics, a numerical technique based on a universal low-pass filter and one based on random wave functions are introduced. The high accuracy of the approximate calculations are checked by comparison with the exact quantum-mechanical solutions

Energy Scales of Compositional Disorder in Alloy Semiconductors

The study of semiconductor alloys is currently experiencing a renaissance. Alloying is often used to tune the material properties desired for device applications. It allows, for instance, to vary in broad ranges the band gaps responsible for the light absorption and light emission spectra of the materials. The price for this tunability is the extra disorder caused by alloying. In this minireview, we address the features of the unavoidable disorder caused by statistical fluctuations of the alloy composition along the device. Combinations of material parameters responsible for the alloy disorder are revealed, based solely on the physical dimensions of the input parameters. Theoretical estimates for the energy scales of the disorder landscape are given separately for several kinds of alloys desired for applications in modern optoelectronics. Among these are perovskites, transition-metal dichalcogenide monolayers, and organic semiconductor blends. While theoretical estimates for perovskites and inorganic monolayers are compatible with experimental data, such a comparison is rather controversial for organic blends, indicating that more research is needed in the latter case

Energy Scales of Compositional Disorder in Alloy Semiconductors

The study of semiconductor alloys is currently experiencing a renaissance. Alloying is often used to tune the material properties desired for device applications. It allows, for instance, to vary in broad ranges the band gaps responsible for the light absorption and light emission spectra of the materials. The price for this tunability is the extra disorder caused by alloying. In this mini review, we address the features of the unavoidable disorder caused by statistical fluctuations of the alloy composition along the device. Combinations of material parameters responsible for the alloy disorder are revealed, based solely on the physical dimensions of the input parameters. Theoretical estimates for the energy scales of the disorder landscape are given separately for several kinds of alloys desired for applications in modern optoelectronics. Among these are perovskites, transition-metal dichalcogenide monolayers, and organic semiconductor blends. While theoretical estimates for perovskites and inorganic monolayers are compatible with experimental data, such a comparison is rather controversial for organic blends, indicating that more research is needed in the latter case

Comment on Interplay of Structural and Optoelectronic Properties in Formamidinium Mixed Tin-Lead Triiodide Perovskites

Studying optoelectronic properties in FAPb(1-x)Sn(x)I(3) and in FA(0.83)Cs(0.17)Pb(1-x)Sn(x)I(3) perovskites as a function of the lead:tin content, Parrott et al. (2018) and Savill et al. (2020) observed the broadest luminescence linewidth and the largest Stokes shift in mixed compositions with Sn 85%. It is in contrast to the intuitive expectation of the largest effects of alloy disorder for the 50:50 composition. This comment addresses the alloy disorder caused by statistical local spatial fluctuations of the alloy composition and shows that the largest effects of alloy disorder for perfectly random fluctuations in FAPb(1-x)Sn(x)I(3) and FA(0.83)Cs(0.17)Pb(1-x)Sn(x)I(3) are, in fact, expected for x 0.85. It can be one of the reasons why Pb-rich and Sn-rich Sn-Pb perovskites typically show shorter photoluminescence (PL) lifetimes, broader emission, increased Stokes shifts, reduced PL quantum yield, and higher Urbach tails, compared with their lead-only counterparts

Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions

Lateral heterojunctions of atomically precise graphene nanoribbons (GNRs) hold promise for applications in nanotechnology, yet their charge transport and most of the spectroscopic properties have not been investigated. Here, we synthesize a monolayer of multiple aligned heterojunctions consisting of quasi-metallic and wide-bandgap GNRs, and report characterization by scanning tunneling microscopy, angle-resolved photoemission, Raman spectroscopy, and charge transport. Comprehensive transport measurements as a function of bias and gate voltages, channel length, and temperature reveal that charge transport is dictated by tunneling through the potential barriers formed by wide-bandgap GNR segments. The current-voltage characteristics are in agreement with calculations of tunneling conductance through asymmetric barriers. We fabricate a GNR heterojunctions based sensor and demonstrate greatly improved sensitivity to adsorbates compared to graphene based sensors. This is achieved via modulation of the GNR heterojunction tunneling barriers by adsorbates. Here, the authors characterize the spectroscopic and transport properties of heterojunctions composed of quasi-metallic and semiconducting graphene nanoribbons (GNRs) with different widths, showing a predominant quantum tunnelling mechanism. The GNR heterojunctions can also be used to realize adsorbate sensors with high sensitivity