Andrew Lewis Ressler

Bio: Andrew Lewis Ressler is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

Quantum Computation and Quantum Information

Abstract: Part I. Fundamental Concepts: 1. Introduction and overview 2. Introduction to quantum mechanics 3. Introduction to computer science Part II. Quantum Computation: 4. Quantum circuits 5. The quantum Fourier transform and its application 6. Quantum search algorithms 7. Quantum computers: physical realization Part III. Quantum Information: 8. Quantum noise and quantum operations 9. Distance measures for quantum information 10. Quantum error-correction 11. Entropy and information 12. Quantum information theory Appendices References Index.

Conservative logic

Abstract: Conservative logic is a comprehensive model of computation which explicitly reflects a number of fundamental principles of physics, such as the reversibility of the dynamical laws and the conservation of certain additive quantities (among which energy plays a distinguished role). Because it more closely mirrors physics than traditional models of computation, conservative logic is in a better position to provide indications concerning the realization of high-performance computing systems, i.e., of systems that make very efficient use of the "computing resources" actually offered by nature. In particular, conservative logic shows that it is ideally possible to build sequential circuits with zero internal power dissipation. After establishing a general framework, we discuss two specific models of computation. The first uses binary variables and is the conservative-logic counterpart of switching theory; this model proves that universal computing capabilities are compatible with the reversibility and conservation constraints. The second model, which is a refinement of the first, constitutes a substantial breakthrough in establishing a correspondence between computation and physics. In fact, this model is based on elastic collisions of identical "balls" and thus is formally identical with the atomic model that underlies the (classical) kinetic theory of perfect gases. Quite literally, the functional behavior of a general-purpose digital computer can be reproduced by a perfect gas placed in a suitably shaped container and given appropriate initial conditions.

Reversible electronic logic using switches

Abstract: Two methods of using switches to implement reversible computations are discussed. The first method has an energy dissipation which is proportional to the square of the error in the voltage, while the second method has an energy dissipation which can in principle be reduced indefinitely by slowing the speed of computation. The first method is basically an extension to 'pass logic' which has been previously used with both nMOS (hot clock nMOS) and CMOS transmission gates to achieve low energy dissipation. The second method is a novel thermodynamically reversible logic system based on CCD-like operations which switches charge packets in a reversible fashion to achieve low energy dissipation.

Two types of mechanical reversible logic

Abstract: The author describes two types of mechanical reversible logic which eliminate sliding contact. In the first type, contact between parts, when it does occur, involves only pressure. In the second, all contact between parts is eliminated. The entire computation could in principle be performed by a single block of complexly shaped oscillating material. The state of the computation is stored in the elastic deformations of this single block. If the material is perfectly elastic, the resulting computer will dissipate no energy. Real material moving sufficiently slowly can approximate a perfectly elastic material as closely as desired. In real materials, energy dissipation occurs during successive cycles of compression and decompression of the material much as energy dissipation occurs when a gas is compressed by a piston. However, at sufficiently low temperatures, this mechanism of energy dissipation might no longer be operative. It is not impossible that energy dissipation can be made to fall exponentially as both temperature and speed of operation are reduced.

Reversibility for efficient computing

Abstract: Today's computers are based on irreversible logic devices, which have been known to be fundamentally energy-inefficient for several decades. Recently, alternative reversible logic technologies have improved rapidly, and are now becoming practical. In traditional models of computation, pure reversibility seems to decrease overall computational efficiency; I provide a proof to this effect. However, traditional models ignore important physical constraints on information processing. This thesis gives the first analysis demonstrating that in a realistic model of computation that accounts for thermodynamic issues, as well as other physical constraints, the judicious use of reversible computing can strictly increase asymptotic computational efficiency, as machine sizes increase. I project real benefits for supercomputing at a large (but achievable) scale in the fairly near term. And with proposed future computing technologies, I show that reversibility will benefit computing at all scales. Next, the thesis demonstrates that reversible computing techniques do not make computer design much more difficult. I describe how to design asymptotically efficient processors using an “adiabatic” reversible electronic logic technology that can be built with today's microprocessor fabrication processes. I describe a simple universal reversible parallel processor chip that our group recently fabricated, and a reversible instruction set for a more traditional RISC-style uniprocessor. Finally, I describe techniques for programming reversible computers. I present a high-level language and a compiler suitable for coding efficient reversible algorithms, and I describe a variety of example algorithms, including efficient reversible sorting, searching, arithmetic, matrix, and graph algorithms. As an example application, I present a linear-time, constant-space reversible program for simulating the Schrodinger wave equation of quantum mechanics. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)