Dmitry Solenov

Optimization of Enzymatic Biochemical Logic for Noise Reduction and Scalability: How Many Biocomputing Gates Can Be Interconnected in a Circuit?

We report an experimental evaluation of the input-output surface for a biochemical AND gate. The obtained data are modeled within the rate-equation approach, with the aim to map out the gate function and cast it in the language of logic variables appropriate for analysis of Boolean logic for scalability. In order to minimize analog noise, we consider a theoretical approach for determining an optimal set for the process parameters to minimize analog noise amplification for gate concatenation. We establish that under optimized conditions, presently studied biochemical gates can be concatenated for up to order 10 processing steps. Beyond that, new paradigms for avoiding noise buildup will have to be developed. We offer a general discussion of the ideas and possible future challenges for both experimental and theoretical research for advancing scalable biochemical computing.

Quantum control of a spin qubit coupled to a photonic crystal cavity

Using a long-lived quantum-dot spin qubit coupled to a GaAs-based photonic crystal cavity, researchers demonstrate complete quantum control of an electron spin qubit. By cleverly controlling the charge state of the InAs quantum dot using laser pulses, optical initialization, control and readout of an electron spin are achieved.

Continuous-time quantum walks on a cycle graph

We present an analytical treatment of quantum walks on a cycle graph. The investigation is based on a realistic physical model of the graph in which decoherence is induced by continuous monitoring of each graph vertex with a nearby quantum point contact. We derive an analytical expression of the probability distribution along the cycle. An upper-bound estimate to the mixing time is shown.

Thermodynamical stability of odd-frequency superconducting state

Odd-frequency pairing mechanism has been investigated for several decades. Nevertheless the properties of such superconducting phase as well as its thermodynamic stability have remained unclear. In particular it has been argued by numerous authors that the odd-frequency state is thermodynamically unstable, has an unphysical Meissner effect (at least within the mean-field approximation), and therefore can not exist as a homogeneous phase in equilibrium physical systems. We argue that such a conclusion is incorrect because it relies on an inappropriate assumption that the odd-frequency superconductor can be described by an effective Hamiltonian that breaks the U(l) symmetry. We show that the odd-frequency state can be appropriately formulated within the functional integral representation by using the effective action to describe such a superconducting state within the mean field approximation. We find that the odd-frequency superconductor is thermodynamically stable and exhibits ordinary Meissner effect, and therefore, in principle, it can be realized in equilibrium solid state systems.

Adsorbate Transport on Graphene by Electromigration

Chemical functionalization of graphene holds promise for various applications ranging from nanoelectronics to catalysis, drug delivery, and nanoassembly. In many applications it is important to be able to transport adsorbates on graphene in real time. We propose to use electromigration to drive the adsorbate transport across the graphene sheet. To assess the efficiency of electromigration, we develop a tight-binding model of electromigration of an adsorbate on graphene and obtain simple analytical expressions for different contributions to the electromigration force. Using experimentally accessible parameters of realistic graphene-based devices as well as electronic structure theory calculations to parametrize the developed model, we argue that electromigration on graphene can be efficient. As an example, we show that the drift velocity of atomic oxygen covalently bound to graphene can reach ~1 cm/s.

Exchange interaction, entanglement, and quantum noise due to a thermal bosonic field

In this work, we investigate the two competing physical effects of a thermalized bosonic environment bath in which two qubits are immersed. Specifically, the induced interaction, which is effectively a zero-temperature effect, and the quantum noise, originating from the same bath modes, are derived within a uniform treatment. We study the dependence of the induced coherent vs noise decoherence effects on the parameters of the bath modes, the qubit system, and their coupling, as well as on the geometry. Specific applications are given for spins interacting with phonons in semiconductors.

Nonunitary quantum walks on hypercycles

We present analytical treatment of quantum walks on multidimensional hypercycle graphs. We derive the analytical expression of the probability distribution for strong and weak decoherence regimes. Upper bound to mixing time is obtained.

Quantum phase transition in the multimode Dicke model

An investigation of the quantum phase transition in both discrete and continuum field Dicke models is presented. A series of anticrossing features following the criticality is revealed in the band of the field modes. Critical exponents are calculated. We investigate the properties of a pairwise entanglement measured by a concurrence and obtain analytical results in the thermodynamic limit.

Electromigration of bivalent functional groups on graphene

Chemical functionalization of graphene holds promise for various applications ranging from nanoelectronics to catalysis, drug delivery, and nano-assembly. In many of these applications it is critical to assess the rates of electromigration - directed motion of adsorbates along the surface of current-carrying graphene due to the electron wind force. In this paper, we develop an accurate analytical theory of electromigration of bivalent functional groups (epoxide, amine) on graphene. Specifically, we carefully analyze various factors contributing to the electron wind force, such as lattice effects and strong scattering beyond Born approximation, and derive a simple analytical expression for this force. Further, we perform accurate electronic structure theory calculations to parameterize the obtained analytical expression. The obtained results can be generalized to different functional groups and adsorbates, e.g., alkali atoms on graphene.

Tunable adsorbate-adsorbate interactions on graphene.

We propose a mechanism to control the interaction between adsorbates on graphene. The interaction between a pair of adsorbates--the change in adsorption energy of one adsorbate in the presence of another--is dominated by the interaction mediated by graphenes π electrons and has two distinct regimes. Ab initio density functional, numerical tight-binding, and analytical calculations are used to develop the theory. We demonstrate that the interaction can be tuned in a wide range by adjusting the adsorbate-graphene bonding or the chemical potential.