At its most fundamental level, circuit-based quantum computation relies on the application of controlled phase shift operations on quantum registers. While these operations are generally compromised by noise and imperfections, quantum gates based on geometric phase shifts can provide intrinsically fault-tolerant quantum computing. Here we demonstrate the high-fidelity realization of a recently ...

Future fault-tolerant quantum computers will require storing and processing data in logical qubits. Here we realize a suite of operations on distance-2 surface code qubit built from seven physical qubits stabilized using repeated error-detection cycles. Logical include initialization into arbitrary states, measurement the cardinal bases Bloch sphere universal set single-qubit gates. For each ty...

In order to use quantum error-correcting codes to actually improve the performance of a quantum computer, it is necessary to be able to perform operations fault-tolerantly on encoded states. I present a general theory of fault-tolerant operations based on symmetries of the code stabilizer. This allows a straightforward determination of which operations can be performed fault-tolerantly on a giv...

A universal quantum computer can be constructed using abelian anyons. Two qubit quantum logic gates such as controlled-NOT operations are performed using topolog-ical effects. Single-anyon operations such as hopping from site to site on a lattice suffice to perform all quantum logic operations. Quantum computation using abelian anyons shares some but not all of the robustness of quantum computa...

Fault tolerant systems comprise of subsystems that interact with each other in complex ways [Joh89]. As a result, modeling the reliability of these systems calls for sophisticated analytical techniques. A powerful technique to address this issue is dynamic fault tree analysis [Dug92]. But because the semantics on which Dynamic Fault Trees are based are themselves complex, there was a question o...

Polymorphic gates are unconventional logic components which can switch their logic functions according to changing environment. The first part of this study presents an evolutionary approach to the design of polymorphic modules which exhibit different logic functions in different environments. The most complicated circuit that we evolved contains more than 100 gates. The second part of this stu...

Quantum error correction and fault-tolerance have provided the possibility for large scale quantum computations without a detrimental loss of quantum information. A very natural class of gates for fault-tolerant quantum computation is the Clifford gate set and as such their usefulness for universal quantum computation is of great interest. Clifford group gates augmented by magic state preparati...

A family of Rydberg blockade gates for neutral-atom qubits is presented, showing how one can significantly reduce the requirements on laser stability and atomic temperature to achieve fault-tolerant quantum computing.

Exploiting recent advances in quantum trapped-ion technologies, we propose a scalable, fault-tolerant quantum computing architecture that overcomes the fundamental challenges of building a full-scale quantum computer and leaves the fabrication a daunting but primarily an engineering concern. Using a hierarchical array-based design and a quantum teleportation communication protocol, we are able ...