We optimize the area and latency of Shor's factoring while simultaneously improving fault tolerance through: (1) balancing the use of ancilla generators, (2) aggressive optimization of error correction, and (3) tuning the core adder circuits. Our custom CAD flow produces detailed layouts of the physical components and utilizes simulation to analyze circuits in terms of area, latency, and success probability. We introduce a metric, called ADCR, which is the probabilistic equivalent of the classic Area-Delay product. Our error correction optimization can reduce ADCR by order of magnitude or more. Contrary to conventional wisdom, we show that the area of an optimized quantum circuit is not dominated exclusively by error

We analyze circuits for kernels from popular quantum computing applications, characterizing the hardware resources necessary to take ancilla preparation off the critical path. The result is a chip entirely dominated by ancilla generation circuits. To address this issue, we introduce optimized ancilla factories and analyze theirstructure and physical layout for ion trap technology. We introduce a new quantum computing architecture with highly concentrated data-only regions surrounded by shared ancilla factories. The results are a reduced dependence on costly teleportation, more efficient distribution of generated ancillae and more than five times speedup over previous proposals.

We show that the problem of communication in a quantum computer reduces to constructing reliable quantum channels by distributing high-fidelity EPR pairs. We develop analytical models of the latency, bandwidth, error rate and resource utilization of such channels, and show that 100s of qubits must be distributed to accommodate a single data communication. Next, we show that a grid of teleportation nodes forms a good substrate on which to distribute EPR pairs. We also explore the control requirements for such a network. Finally, we propose a specific routing architecture and simulate the Quantum Fourier Transform to demonstrate the impact of resource contention.

We investigate coding techniques to reduce the energy consumed by on-chip buses in a microprocessor. We explore several simple coding schemes and simulate them using a modified SimpleScalar simulator and SPEC benchmarks. We show an average of 35% savings in transitions on internal buses. To quantify actual power savings, we design a dictionary based encoder/decoder circuit in a 0.13 /spl mu/m process, extract it as a netlist, and simulate its behavior under SPICE. Utilizing a realistic wire model with repeaters, we show that we can break even at median wire length scales of less than 11.5 mm at 0.13 /spl mu/ and project a break-even point of 2.7 mm for a larger design at 0.07 /spl mu/.

As quantum computing moves closer to reality the need for basic architectural studies becomes more pressing. Quantum wires, which transport quantum data, will be a fundamental component in all anticipated silicon quantum architectures. Since they cannot consist of a stream of electrons, as in the classical case, quantum wires must fundamentally be designed differently. In this paper, we present two quantum wire designs: a swap wire, based on swapping of adjacent qubits, and a teleportation wire, based on the quantum teleportation primitive. We characterize the latency and bandwidth of these two alternatives in a device-independent way. Furthermore, unlike classical wires, quantum wires need control signals in order to operate. We explore the complexity of the control mechanisms and the fundamental tension between the scale of quantum effects and the scale of the classical logic needed to control them. This "pitch-matching" problem imposes constraints on minimum wire lengths and wire intersections, leading us to use a SIMD approach for the control mechanisms. We ultimately show that qubit decoherence imposes a basic limit on the maximum communication distance of the swapping wire, while relatively large overhead imposes a basic limit on the minimum communication distance of the teleportation wire.