Papers by Alexey Melnikov
How useful can machine learning be in a quantum laboratory? Here we raise the question of the pot... more How useful can machine learning be in a quantum laboratory? Here we raise the question of the potential of intelligent machines in the context of scientific research. A major motivation for the present work is the unknown reachability of various entanglement classes in quantum experiments. We investigate this question by using the projective simulation model, a physics-oriented approach to artificial intelligence. In our approach, the projective simulation system is challenged to design complex photonic quantum experiments that produce high-dimensional entangled multi-photon states, which are of high interest in modern quantum experiments. The artificial intelligence system learns to create a variety of entangled states, and improves the efficiency of their realization. In the process, the system autonomously (re)discovers experimental techniques which are only now becoming standard in modern quantum optical experiments – a trait which was not explicitly demanded from the system but emerged through the process of learning. Such features highlight the possibility that machines could have a significantly more creative role in future research.
We study the entanglement dynamics of two electrons in a dissipative quantum walk on a cycle grap... more We study the entanglement dynamics of two electrons in a dissipative quantum walk on a cycle graph. The considered dissipation, which is inevitably induced by coupling to a measurement apparatus, can make the quantum system unreliable by breaking entanglement between two electrons. However for certain realistic parameters a distinct maximum of fermionic entanglement can be established and entanglement revival can be observed.
Learning models of artificial intelligence can nowadays perform very well on a large variety of t... more Learning models of artificial intelligence can nowadays perform very well on a large variety of tasks. However, in practice different task environments are best handled by different learning models, rather than a single, universal, approach. Most non-trivial models thus require the adjustment of several to many learning parameters, which is often done on a case-by-case basis by an external party. Meta-learning refers to the ability of an agent to autonomously and dynamically adjust its own learning parameters, or meta-parameters. In this work we show how projective simulation, a recently developed model of artificial intelligence, can naturally be extended to account for meta-learning in reinforcement learning settings. The projective simulation approach is based on a random walk process over a network of clips. The suggested meta-learning scheme builds upon the same design and employs clip networks to monitor the agent's performance and to adjust its meta-parameters " on the fly ". We distinguish between " reflexive adaptation " and " adaptation through learning " , and show the utility of both approaches. In addition, a trade-off between flexibility and learning-time is addressed. The extended model is examined on three different kinds of reinforcement learning tasks, in which the agent has different optimal values of the meta-parameters, and is shown to perform well, reaching near-optimal to optimal success rates in all of them, without ever needing to manually adjust any meta-parameter.
В работе представлены исследования квантовых блужданий электронов в одномерной решетке из квантов... more В работе представлены исследования квантовых блужданий электронов в одномерной решетке из квантовых точек в кремнии. Квантовые блуждания представляют особый интерес для квантовой теории информации. В статье предложен способ создания запутанных пар идентичных частиц для последующего использования при обработке информации. Показано, что при определенных конфигурациях кольца из квантовых точек возможно создать периодические колебания величины фермионной запутанности. Учтено неустранимое влияние окружения на электроны, вызывающее предполагаемое периодическое разрушение запутанности с последую- щим ее созданием. Данный эффект возможно использовать для контроля запутанности путем остановки блужданий в определенный момент времени повышением потенциальных барьеров.
Показатель устойчивости коллекции к изменениям в моде определяет способность ассортимента соответ... more Показатель устойчивости коллекции к изменениям в моде определяет способность ассортимента соответствовать модным тенденциям на протяжении определенного периода времени и позволяет рассчитать оптимальное прогнозируемое количество продукции, которая будет востребована рынком.
We study the entanglement structure dynamics of multipartite system experiencing a dissipative ev... more We study the entanglement structure dynamics of multipartite system experiencing a dissipative evolution. We characterize processes leading to a particular form of output system entanglement and provide a recipe for their identification via concatenations of peculiar linear maps with entanglementbreaking operations. We illustrate the applicability of our approach by considering local and global depolarizing noises acting on general multiqubit states. The difference in typical entanglement behavior of systems subjected to these noises is observed: the originally genuine entanglement dissociates by splitting particles one by one in case of local noise, whereas the intermediate stages of entanglement clustering are present in case of global noise. We also analyze the definitive phase of evolution when the annihilation of entanglement compound finally takes place.
Coherent controlization, i.e., coherent conditioning of arbitrary single- or multi-qubit operatio... more Coherent controlization, i.e., coherent conditioning of arbitrary single- or multi-qubit operations on the state of one or more control qubits, is an important ingredient for the flexible implementation of many algorithms in quantum computation. This is of particular significance when certain subroutines are changing over time or when they are frequently modified, such as in decision-making algorithms for learning agents. We propose a scheme to realize coherent controlization for any number of superconducting qubits coupled to a microwave resonator. For two and three qubits, we present an explicit construction that is of high relevance for quantum learning agents. We demonstrate the feasibility of our proposal, taking into account loss, dephasing, and the cavity self-Kerr effect.
The ability to generalize is an important feature of any intelligent agent. Not only because it m... more The ability to generalize is an important feature of any intelligent agent. Not only because it may allow the agent to cope with large amounts of data, but also because in some environments, an agent with no generalization capabilities cannot learn. In this work we outline several criteria for generalization, and present a dynamic and autonomous machinery that enables projective simulation agents to meaningfully generalize. Projective simulation, a novel, physical approach to artificial intelligence, was recently shown to perform well in standard reinforcement learning problems, with applications in advanced robotics as well as quantum experiments. Both the basic projective simulation model and the presented generalization machinery are based on very simple principles. This allows us to provide a full analytical analysis of the agent’s performance and to illustrate the benefit the agent gains by generalizing. Specifically, we show that already in basic (but extreme) environments, learning without generalization may be impossible, and demonstrate how the presented generalization machinery enables the projective simulation agent to learn.
We study the model of projective simulation (PS) which is a novel approach to artificial intellig... more We study the model of projective simulation (PS) which is a novel approach to artificial intelligence (AI). Recently it was shown that the PS agent performs well in a number of simple task environments, also when compared to standard models of reinforcement learning (RL). In this paper we study the performance of the PS agent further in more complicated scenarios. To that end we chose two well-studied benchmarking problems, namely the “grid-world” and the “mountain-car” problem, which challenge the model with large and continuous input space. We compare the performance of the PS agent model with those of existing models and show that the PS agent exhibits competitive performance also in such scenarios.
We study a continuous-time quantum walk of interacting fermions on a cycle graph. By finding anal... more We study a continuous-time quantum walk of interacting fermions on a cycle graph. By finding analytical solutions and simulating the dynamics of two fermions we observe a diverse structure of entangled states of indistinguishable fermions. The relation between entanglement of distinguishable qutrits and indistinguishable electrons is observed. Restrictions imposed by the symmetry of a cycle graph are derived. Possible realization of a quantum walk in an array of semiconductor quantum dots is discussed.
Russian Microelectronics, 2013
ABSTRACT The interaction of the quantum register with a noisy environment that leads to phase and... more ABSTRACT The interaction of the quantum register with a noisy environment that leads to phase and bit errors is considered. Modeling of 5-qubit and 9-qubit error-correction algorithms for various environments is performed. It is shown that the use of the quantum correction leads to a quadratic decrease in the error probability. The efficiency of applying the 5-qubit algorithm of error correction for a silicon double-dot qubit is shown.
International Conference Micro- and Nano-Electronics 2012, 2013
We considered the interaction of semiconductor quantum register with noisy environment leading to... more We considered the interaction of semiconductor quantum register with noisy environment leading to various types of qubit errors. We analysed both phase and amplitude decays during the process of electron-phonon interaction. The performance of quantum error correction codes (QECC) which will be inevitably used in full scale quantum information processors was studied in realistic conditions in semiconductor nanostructures. As a hardware basis for quantum bit we chose the quantum spatial states of single electron in semiconductor coupled double quantum dot system. The modified 5and 9-qubit quantum error correction (QEC) algorithms by Shor and DiVincenzo without error syndrome extraction were applied to quantum register. 5-qubit error correction procedures were implemented for Si charge double dot qubits in the presence of acoustic phonon environment. χmatrix, Choi-Jamio lkowski state and measure of decoherence techniques were used to quantify qubit fault-tolerance. Our results showed that the introduction of above quantum error correction techniques at small phonon noise levels provided quadratic improvement of output error rates. The efficiency of 5-qubits quantum error correction algorithm in semiconductor quantum information processors was demonstrated. * Electronic address: [email protected] † Electronic address: [email protected]; Also at NIX, Moscow, Russia arXiv:1210.6590v1 [quant-ph]
Quantum walks have been employed widely to develop new tools for quantum information processing r... more Quantum walks have been employed widely to develop new tools for quantum information processing recently. A natural quantum walk dynamics of interacting particles can be used to implement efficiently the universal quantum computation. In this work quantum walks of electrons on a graph are studied. The graph is composed of semiconductor quantum dots arranged in a circle. Electrons can tunnel between adjacent dots and interact via Coulomb repulsion, which leads to entanglement. Fermionic entanglement dynamics is obtained and evaluated.
We study the entanglement structure dynamics of multipartite system experiencing a dissipative ev... more We study the entanglement structure dynamics of multipartite system experiencing a dissipative evolution. We characterize processes leading to a particular form of output system entanglement and provide a recipe for their identification via concatenations of peculiar linear maps with entanglementbreaking operations. We illustrate the applicability of our approach by considering local and global depolarizing noises acting on general multiqubit states. The difference in typical entanglement behavior of systems subjected to these noises is observed: the originally genuine entanglement dissociates by splitting particles one by one in case of local noise, whereas the intermediate stages of entanglement clustering are present in case of global noise. We also analyze the definitive phase of evolution when the annihilation of entanglement compound finally takes place.
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Papers by Alexey Melnikov