Robin Harper

Robin Harper
The University of Sydney

PhD

About

28
Publications
4,570
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,096
Citations
Introduction
Robin Harper currently works at University of Sydney in Quantum Information Theory. His current research centres around Quantum Characterisation Control and Verification.

Publications

Publications (28)
Preprint
Full-text available
Benchmarking and characterising quantum states and logic gates is essential in the development of devices for quantum computing. We introduce a Bayesian approach to self-consistent process tomography, called fast Bayesian tomography (FBT), and experimentally demonstrate its performance in characterising a two-qubit gate set on a silicon-based spin...
Article
Full-text available
As quantum computers approach the fault-tolerance threshold, diagnosing and characterizing the noise on large-scale quantum devices is increasingly important. One of the most important classes of noise channels is the class of Pauli channels, for reasons of both theoretical tractability and experimental relevance. Here we present a practical algori...
Article
Full-text available
Noise is the central obstacle to building large-scale quantum computers. Quantum systems with sufficiently uncorrelated and weak noise could be used to solve computational problems that are intractable with current digital computers. There has been substantial progress towards engineering such systems1–8. However, continued progress depends on the...
Preprint
As quantum computers approach the fault tolerance threshold, diagnosing and characterizing the noise on large scale quantum devices is increasingly important. One of the most important classes of noise channels is the class of Pauli channels, for reasons of both theoretical tractability and experimental relevance. Here we present a practical algori...
Preprint
Noise is the central obstacle to building large-scale quantum computers. Quantum systems with sufficiently uncorrelated and weak noise could be used to solve computational problems that are intractable with current digital computers. There has been substantial progress towards engineering such systems. However, continued progress depends on the abi...
Article
Randomized benchmarking and variants thereof, which we collectively call RB+, are widely used to characterize the performance of quantum computers because they are simple, scalable, and robust to state-preparation and measurement errors. However, experimental implementations of RB+ allocate resources suboptimally and make ad-hoc assumptions that un...
Article
Full-text available
Spin qubits created from gate-defined silicon metal–oxide–semiconductor quantum dots are a promising architecture for quantum computation. The high single qubit fidelities possible in these systems, combined with quantum error correcting codes, could potentially offer a route to fault-tolerant quantum computing. To achieve fault tolerance, however,...
Article
Quantum computers will require encoding of quantum information to protect them from noise. Fault-tolerant quantum computing architectures illustrate how this might be done but have not yet shown a conclusive practical advantage. Here we demonstrate that a small but useful error detecting code improves the fidelity of the fault-tolerant gates implem...
Preprint
Randomized benchmarking and variants thereof, which we collectively call RB+, are widely used to characterize the performance of quantum computers because they are simple, scalable, and robust to state-preparation and measurement errors. However, experimental implementations of RB+ allocate resources suboptimally and make ad-hoc assumptions that un...
Preprint
Full-text available
The performance requirements for fault-tolerant quantum computing are very stringent. Qubits must be manipulated, coupled, and measured with error rates well below 1%. For semiconductor implementations, silicon quantum dot spin qubits have demonstrated average single-qubit Clifford gate fidelities of 99.86% in isotopically enriched 28Si/SiGe device...
Preprint
Full-text available
Quantum computers will require encoding of quantum information to protect them from noise. Fault-tolerant quantum computing architectures illustrate how this might be done, but have not yet shown a conclusive practical advantage. Here we demonstrate that a small but useful error detecting code improves the fidelity of the fault-tolerant gates imple...
Article
We propose a framework for the systematic and quantitative generalization of Bell's theorem using causal networks. We first consider the multi-objective optimization problem of matching observed data while minimizing the causal effect of nonlocal variables and prove an inequality for the optimal region that both strengthens and generalizes Bell's t...
Article
Randomized benchmarking (RB) is an important protocol for robustly characterizing the error rates of quantum gates. The technique is typically applied to the Clifford gates since they form a group that satisfies a convenient technical condition of forming a unitary 2-design, in addition to having a tight connection to fault-tolerant quantum computi...
Article
Full-text available
The fidelity of laser-driven quantum logic operations on trapped ion qubits tend to be lower than microwave-driven logic operations due to the difficulty of stabilizing the driving fields at the ion location. Through stabilization of the driving optical fields and use of composite pulse sequences, we demonstrate high fidelity single-qubit gates for...
Article
Full-text available
Noise mechanisms in quantum systems can be broadly characterized as either coherent (i.e., unitary) or incoherent. For a given fixed average error rate, coherent noise mechanisms will generally lead to a larger worst-case error than incoherent noise. We show that the coherence of a noise source can be quantified by the unitarity, which we relate to...
Article
Full-text available
We show that non-exponential fidelity decays in randomized benchmarking experiments on quantum dot qubits are consistent with numerical simulations that incorporate low-frequency noise. By expanding standard randomized benchmarking analysis to this experimental regime, we find that such non-exponential decays are better modeled by multiple exponent...
Article
Full-text available
Evo Robocode is a competition where the challenge is to use evolutionary techniques to create a Java based controller for a simulated robot tank. The tank competes in a closed arena against other such tanks. The Robocode game is a programming platform that allows such tanks to compete. This article discusses the use of Grammatical Evolution (a form...
Conference Paper
Full-text available
Genetic programming (GP) is not a field noted for the rigor of its benchmarking. Some of its benchmark problems are popular purely through historical contingency, and they can be criticized as too easy or as providing misleading information concerning real-world performance, but they persist largely because of inertia and the lack of good alternati...
Article
Operator equalisation is a methodology inspired by the cross-over bias theory that attempts to limit bloat in genetic programming (GP). This paper examines a bivariate regression problem and demonstrates that operator equalisation suffers from bloat like behaviour when attempting to solve this problem. This is in contrast to a spatial co-evolutiona...
Conference Paper
Robocode is a Java based programming platform where robot tanks, controlled by programs written in Java, compete. In this paper Grammatical Evolution is used to evolve Java programs to control a Robocode robot. This paper demonstrates how Grammatical Evolution together with spatial co-evolution in age layered planes (SCALP) can harness co-evolution...
Conference Paper
In this paper, I describe how to use Grammatical Evolution to implement a parameterized Lindenmayer System (L-System), where the number of production rules of the L-System is determined by the genome of the individual, rather than being determined by the user before hand. This leaves the number of production rules as a free parameter and allows the...
Conference Paper
This paper explores some of the initialisation schemes that can be used to create the starting population of a Grammatical Evolution (GE) run. It investigates why two typical initialisation schemes (random bit and ramped half and half) produce very different, but in each case skewed, tree types. A third methodology, Sean Luke's Probabilistic Tree-C...
Conference Paper
This paper introduces a method of combining Greg Hornby's Age Layered Protocol System with a form of spatial co-evolution. The combined system (SCALP) is compared to these two systems and a canonical GP tournament selection scheme over three well understood domains, the sextic regression problem, a two variable regression problem and a variation on...
Conference Paper
This paper re-visits the minesweeper problem, one of the problems used by Koza in his 1994 book, Genetic Programming II, Advances in Genetic Programming. The minesweeper problem was one of the many problems used to demonstrate how the Automatically Defined Function methodology could solve problems not able to be solved (in this case) with a no func...
Conference Paper
Full-text available
This paper compares the efficacy of different crossover operators for Grammatical Evolution across a typical numeric regression problem and a typical data classification problem. Grammatical evolution is an extension of genetic programming, in that it is an algorithm for evolving complete programs in an arbitrary language. Each of the two main cros...
Conference Paper
Full-text available
Grammatical evolution is an extension of genetic programming, in that it is an algorithm for evolving complete programs in an arbitrary language. By utilising a Backus Naur form grammar the advantages of typing are achieved as well as a separation of genotype and phenotype. This paper introduces a meta-grammar into grammatical evolution allowing th...
Conference Paper
Full-text available
Grammatical evolution is an algorithm for evolving complete programs in an arbitrary language. By utilising a Backus Naur Form grammar the advantages of typing are achieved. A separation of genotype and phenotype allows the implementation of operators that manipulate (for instance by crossover and mutation) the genotype (in grammatical evolution -...

Network

Cited By