Resilient entangling gates for trapped ions

Constructing a large-scale ion trap quantum processor will require entangling gate operations that are robust in the presence of noise and experimental imperfection. We experimentally demonstrate how a new type of Mølmer-Sørensen gate protects against infidelity caused by heating of the motional mode used during the gate. Furthermore, we show how the same technique simultaneously provides significant protection against slow fluctuations and mis-sets in the secular frequency. Since this parameter sensitivity is worsened in cases where the ions are not ground-state cooled, our method provides a path towards relaxing ion cooling requirements in practical realizations of quantum computing and simulation

GPUVerify: A Verifier for GPU Kernels

We present a technique for verifying race- and divergence-freedom of GPU kernels that are written in mainstream ker-nel programming languages such as OpenCL and CUDA. Our approach is founded on a novel formal operational se-mantics for GPU programming termed synchronous, delayed visibility (SDV) semantics. The SDV semantics provides a precise definition of barrier divergence in GPU kernels and allows kernel verification to be reduced to analysis of a sequential program, thereby completely avoiding the need to reason about thread interleavings, and allowing existing modular techniques for program verification to be leveraged. We describe an efficient encoding for data race detection and propose a method for automatically inferring loop invari-ants required for verification. We have implemented these techniques as a practical verification tool, GPUVerify, which can be applied directly to OpenCL and CUDA source code. We evaluate GPUVerify with respect to a set of 163 kernels drawn from public and commercial sources. Our evaluation demonstrates that GPUVerify is capable of efficient, auto-matic verification of a large number of real-world kernels

Formal Verification of Parallel Prefix Sum

ISSN:0302-9743ISSN:1611-334

Making Software Verification Tools Really Work

We discuss problems and barriers which stand in the way of producing verification tools that are robust, scalable and integrated in the software development cycle. Our analysis is that these barriers span a spectrum from theoretical, through practical and even logistical issues. Theoretical issues are the inherent complexity of program verification and the absence of a common, accepted semantic model in tools. Practical hurdles include the challenges arising from real-world systems features, such as floating-point arithmetic and weak memory. Logistical obstacles we identify are the lack of standard benchmarks to drive tool quality and efficiency, and the difficulty for academic research institutions of allocating resources to tool development. We propose simple measures which we, as a community, could adopt to make the design of serious verification tools easier and more credible. Our long-term vision is for the community to produce tools that are indispensable for a developer but so seamlessly integrated into a development environment, as to be invisible