6,790 research outputs found
Scalable Emulation of Sign-ProblemFree Hamiltonians with Room Temperature p-bits
The growing field of quantum computing is based on the concept of a q-bit
which is a delicate superposition of 0 and 1, requiring cryogenic temperatures
for its physical realization along with challenging coherent coupling
techniques for entangling them. By contrast, a probabilistic bit or a p-bit is
a robust classical entity that fluctuates between 0 and 1, and can be
implemented at room temperature using present-day technology. Here, we show
that a probabilistic coprocessor built out of room temperature p-bits can be
used to accelerate simulations of a special class of quantum many-body systems
that are sign-problemfree or stoquastic, leveraging the well-known
Suzuki-Trotter decomposition that maps a -dimensional quantum many body
Hamiltonian to a +1-dimensional classical Hamiltonian. This mapping allows
an efficient emulation of a quantum system by classical computers and is
commonly used in software to perform Quantum Monte Carlo (QMC) algorithms. By
contrast, we show that a compact, embedded MTJ-based coprocessor can serve as a
highly efficient hardware-accelerator for such QMC algorithms providing several
orders of magnitude improvement in speed compared to optimized CPU
implementations. Using realistic device-level SPICE simulations we demonstrate
that the correct quantum correlations can be obtained using a classical
p-circuit built with existing technology and operating at room temperature. The
proposed coprocessor can serve as a tool to study stoquastic quantum many-body
systems, overcoming challenges associated with physical quantum annealers.Comment: Fixed minor typos and expanded Appendi
Weighted p-bits for FPGA implementation of probabilistic circuits
Probabilistic spin logic (PSL) is a recently proposed computing paradigm
based on unstable stochastic units called probabilistic bits (p-bits) that can
be correlated to form probabilistic circuits (p-circuits). These p-circuits can
be used to solve problems of optimization, inference and also to implement
precise Boolean functions in an "inverted" mode, where a given Boolean circuit
can operate in reverse to find the input combinations that are consistent with
a given output. In this paper we present a scalable FPGA implementation of such
invertible p-circuits. We implement a "weighted" p-bit that combines stochastic
units with localized memory structures. We also present a generalized tile of
weighted p-bits to which a large class of problems beyond invertible Boolean
logic can be mapped, and how invertibility can be applied to interesting
problems such as the NP-complete Subset Sum Problem by solving a small instance
of this problem in hardware
Programmability of Chemical Reaction Networks
Motivated by the intriguing complexity of biochemical circuitry within individual cells we study Stochastic Chemical Reaction Networks (SCRNs), a formal model that considers a set of chemical reactions acting on a finite number of molecules in a well-stirred solution according to standard chemical kinetics equations. SCRNs have been widely used for describing naturally occurring (bio)chemical systems, and with the advent of synthetic biology they become a promising language for the design of artificial biochemical circuits. Our interest here is the computational power of SCRNs and how they relate to more conventional models of computation. We survey known connections and give new connections between SCRNs and Boolean Logic Circuits, Vector Addition Systems, Petri Nets, Gate Implementability, Primitive Recursive Functions, Register Machines, Fractran, and Turing Machines. A theme to these investigations is the thin line between decidable and undecidable questions about SCRN behavior
Model predictive control techniques for hybrid systems
This paper describes the main issues encountered when applying model predictive control to hybrid processes. Hybrid model predictive control (HMPC) is a research field non-fully developed with many open challenges. The paper describes some of the techniques proposed by the research community to overcome the main problems encountered. Issues related to the stability and the solution of the optimization problem are also discussed. The paper ends by describing the results of a benchmark exercise in which several HMPC schemes were applied to a solar air conditioning plant.Ministerio de EduaciĂłn y Ciencia DPI2007-66718-C04-01Ministerio de EduaciĂłn y Ciencia DPI2008-0581
Memory and information processing in neuromorphic systems
A striking difference between brain-inspired neuromorphic processors and
current von Neumann processors architectures is the way in which memory and
processing is organized. As Information and Communication Technologies continue
to address the need for increased computational power through the increase of
cores within a digital processor, neuromorphic engineers and scientists can
complement this need by building processor architectures where memory is
distributed with the processing. In this paper we present a survey of
brain-inspired processor architectures that support models of cortical networks
and deep neural networks. These architectures range from serial clocked
implementations of multi-neuron systems to massively parallel asynchronous ones
and from purely digital systems to mixed analog/digital systems which implement
more biological-like models of neurons and synapses together with a suite of
adaptation and learning mechanisms analogous to the ones found in biological
nervous systems. We describe the advantages of the different approaches being
pursued and present the challenges that need to be addressed for building
artificial neural processing systems that can display the richness of behaviors
seen in biological systems.Comment: Submitted to Proceedings of IEEE, review of recently proposed
neuromorphic computing platforms and system
Complete integrability of information processing by biochemical reactions
Statistical mechanics provides an effective framework to investigate
information processing in biochemical reactions. Within such framework
far-reaching analogies are established among (anti-) cooperative collective
behaviors in chemical kinetics, (anti-)ferromagnetic spin models in statistical
mechanics and operational amplifiers/flip-flops in cybernetics. The underlying
modeling -- based on spin systems -- has been proved to be accurate for a wide
class of systems matching classical (e.g. Michaelis--Menten, Hill, Adair)
scenarios in the infinite-size approximation. However, the current research in
biochemical information processing has been focusing on systems involving a
relatively small number of units, where this approximation is no longer valid.
Here we show that the whole statistical mechanical description of reaction
kinetics can be re-formulated via a mechanical analogy -- based on completely
integrable hydrodynamic-type systems of PDEs -- which provides explicit
finite-size solutions, matching recently investigated phenomena (e.g.
noise-induced cooperativity, stochastic bi-stability, quorum sensing). The
resulting picture, successfully tested against a broad spectrum of data,
constitutes a neat rationale for a numerically effective and theoretically
consistent description of collective behaviors in biochemical reactions.Comment: 24 pages, 10 figures; accepted for publication in Scientific Report
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