EMT/QIS: Robust Quantum Simulation Techniques for Fault-Tolerant Quantum Computation

University Of Washington, Seattle WA

Investigators

Abstract

Quantum computers offer fundamental algorithmic advantages over classical computers and building a quantum computer would fundamentally change the power of our computers. Large scale quantum computers, however, are difficult to build in large part due to the fact that quantum systems interact with their environment and quickly lose their quantum nature. The solution to this problem, at least in theory, was provided by the theory of fault-tolerant quantum computation. The theory of fault-tolerant quantum computation, while providing an in principle demonstration of viability of quantum computers, suffers from requiring protocols that have a severe complexity overhead. As a result of these difficulties, an alternative approach toward building a robust quantum computer has been pursued in which many-body quantum systems protect quantum information by encoding this information in suitable protected degrees of freedom. In this approach the natural physics of the system helps protect the quantum information. A difficulty arises, however, due in part to the complexity required of the engineered quantum system. The research being performed here seeks to overcome this obstacle and open the path for constructing the equivalent of a transistor for quantum computers. Here the investigators study three approaches to engineering effective many-body interactions suitable for protecting quantum information. The first approach involves the construction of fault-tolerant perturbation gadgets. This research involves studying the robustness of the perturbation gadgets. The second approach involves the use of quantum circuits to simulate Hamiltonian dynamics. In this technique, research is performed on new methods for fault-tolerant simulation. A final technique involves the use of time-dependent Hamiltonians and the research involves a detailed study of the errors in this time-dependent construction.