Reversible hardware finds application in emerging areas such as low power circuit design, quantum computing, optical computing, and DNA computing. Intensive research has recently focused on the synthesis of reversible architectures. Most of these approaches derive efficient or even optimal circuits having as major drawback the scalability: they can only handle small circuits (up to a few hundred inputs for the most promising ones). In this paper, we propose a graph-based hierarchical synthesis method for large reversible and quantum architectures which can be combined with any of the existing synthesis methods to deliver unlimited scalability for arbitrary large and/or irregular architectures. The specification of any complex function is provided in the form of a sequential algorithm consisting of primitive pre-synthesized operations available in a library. The components of the library may have been designed by ad-hoc methods or synthesized by the known methods in the literature or even by the proposed synthesis procedure. The synthesized architecture is represented as a dependence graph whose nodes correspond to the available components of the library and their respective inverses so as to reset possible intermediate ancillae bits used during the synthesis procedure back to their initial state. The method can be recursively applied at multiple levels to build any complex reversible or quantum architecture.
Reversible hardware finds application in emerging areas such as low power circuit design, quantum computing, optical computing, and DNA computing. Intensive research has recently focused on the synthesis of reversible architectures. Most of these approaches derive efficient or even optimal circuits having as major drawback the scalability: they can only handle small circuits (up to a few hundred inputs for the most promising ones). In this paper, we propose a graph-based hierarchical synthesis method for large reversible and quantum architectures which can be combined with any of the existing synthesis methods to deliver unlimited scalability for arbitrary large and/or irregular architectures. The specification of any complex function is provided in the form of a sequential algorithm consisting of primitive pre-synthesized operations available in a library. The components of the library may have been designed by ad-hoc methods or synthesized by the known methods in the literature or even by the proposed synthesis procedure. The synthesized architecture is represented as a dependence graph whose nodes correspond to the available components of the library and their respective inverses so as to reset possible intermediate ancillae bits used during the synthesis procedure back to their initial state. The method can be recursively applied at multiple levels to build any complex reversible or quantum architecture.
With the continuous shrinkage of transistor sizes in very large scale integrated circuits, power consumption forms a serious concern to be tackled. With their ability to allow for zero energy dissipation, reversible circuits have been considered as promising solution to meetup with low power design requirements. Moreover, advances in their synthesis methodologies can be easily applied to quantum circuits due to the inherited reversibility of the latter. Although numerous algorithms have been proposed in the literature to synthesize reversible circuits and map them into their corresponding quantum circuits, the scalability and computational effort of such algorithms form a serious concern when synthesizing large size input functions. Binary Decision Diagram-based synthesis for reversible circuits has shown great evidence in realizing reversible circuits with low quantum cost through exploiting proper reduction rules for smaller graph size. However, the order of the variables in the decision diagram impacts its overall size, and thus, the cost of its corresponding reversible circuit. While several reordering algorithms have been proposed in this manner, their direct impact on the quantum cost has not been considered. In this article, a Binary Decision Diagram-based algorithm for reversible circuit synthesis is proposed to synthesize reversible circuits for a given Boolean function with low quantum cost through exploiting a linearized relationship between the decision diagram size and the corresponding quantum cost. Thereafter, different decision diagram reordering algorithms have been integrated with the proposed algorithm and compared in terms of their impact on the quantum cost. Experimental results show that Genetic Algorithm-based reordering for decision diagram, supported with, cycle crossover, inverse mutation, and tournament selection, results in the least quantum cost of the output circuit if compared with other algorithms due to its property in preserving the nodes of the decision diagram in their near-optimal locations during the optimiation recipe.
Reversible logic became a promising alternative to traditional circuits because of its applications in emerging technologies such as quantum computing, low-power design, DNA computing, or nanotechnologies. As a result, synthesis of the respective circuits is an intensely studied topic. However, most synthesis methods are limited, because they rely on a truth table representation of the function to be synthesized. In this paper, the authors present a synthesis approach that is based on Binary Decision Diagrams (BDDs). The authors propose a technique to derive reversible or quantum circuits from BDDs by substituting all nodes of the BDD with a cascade of Toffoli or quantum gates, respectively. Boolean functions containing more than a hundred of variables can efficiently be synthesized. More precisely, a circuit can be obtained from a given BDD using an algorithm with linear worst case behavior regarding run-time and space requirements. Furthermore, using the proposed approach, theoretical results known from BDDs can be transferred to reversible circuits. Experiments show better results (with respect to the circuit cost) and a significantly better scalability in comparison to previous synthesis approaches.
We present a synthesis framework to map logic networks into quantum circuits for quantum computing. The synthesis framework is based on lookup-table (LUT) networks, which play a key role in conventional logic synthesis. Establishing a connection between LUTs in an LUT network and reversible single-target gates in a reversible network allows us to bridge conventional logic synthesis with logic synthesis for quantum computing, despite several fundamental differences. We call our synthesis framework LUT-based hierarchical reversible logic synthesis (LHRS). Input to LHRS is a classical logic network representing an arbitrary Boolean combinational operation; output is a quantum network (realized in terms of Clifford+T gates). The framework allows one to account for qubit count requirements imposed by the overlying quantum algorithm or target quantum computing hardware. In a fast first step, an initial network is derived that only consists of single-target gates and already completely determines the number of qubits in the final quantum network. Different methods are then used to map each single-target gate into Clifford+T gates, while aiming at optimally using available resources. We demonstrate the versatility of our method by conducting a design space exploration using different parameters on a set of large combinational benchmarks. On the same benchmarks, we show that our approach can advance over the state-of-the-art hierarchical reversible logic synthesis algorithms.
Quantum computers, more specifically quantum circuits, take on the eyes with their computational promises such as reversibility. In this paper, we perform synthesis and optimization of quantum circuits. In the first part, we propose a fast synthesis algorithm that implements any given reversible Boolean function with quantum gates. Instead of an exhaustive search on every given function, our algorithm creates a library of essential functions and performs sorting. As an example, to implement 4 bit circuits we only use 120 essential functions out of all 20922789888000 functions. In the second part, we optimize our circuits by using new templates. The proposed templates mainly consist of Toffoli gates with negative and positive controlling lines. These templates also show us that optimum area solutions proposed in the literature are not actually optimum; they can be improved.
Today's rapid advances in the physical implementation of quantum computers demand for scalable synthesis methods in order to map practical logic designs to quantum architectures. We present a synthesis algorithm for quantum computing based on k-LUT networks, which can be derived from Verilog netlists using state-of-the-art and off-the-shelf mapping algorithms. We demonstrate the effectiveness of our method in automatically synthesizing several floating point networks up to double precision. As many quantum algorithms target scientific simulation applications, they can make rich use of floating point arithmetic components. But due to the lack of quantum circuit descriptions for those components, it is not possible to find a realistic cost estimation for the algorithms. Our synthesized benchmarks provide cost estimates that allow quantum algorithm designers to provide the first complete cost estimates for a host of quantum algorithms. This is an essential step towards the goal of understanding which quantum algorithms will be practical in the first generations of quantum computers.
Reversible circuits are an emerging technology where all computations are performed in an invertible manner. Motivated by their promising applications, e.g. in the domain of quantum computation or in the low-power design, the synthesis of such circuits has been intensely studied. However, how to automatically realize reversible circuits with the minimal number of lines for large functions is an open research problem. In this paper, we propose a new synthesis approach which relies on concepts that are complementary to existing ones. While “conventional” function representations have been applied for synthesis so far (such as truth tables, ESOPs, BDDs), we exploit Quantum Multiple-valued Decision Diagrams (QMDDs) for this purpose. An algorithm is presented that performs transformations on this data-structure eventually leading to the desired circuit. Experimental results show the novelty of the proposed approach through enabling automatic synthesis of large reversible functions with the minimal number of circuit lines. Furthermore, the quantum cost of the resulting circuits is reduced by 50% on average compared to an existing state-of-the-art synthesis method.