Spin networks, quantum automata and link invariants (original) (raw)

Quantum automata, braid group and link polynomials

2006

The spin--network quantum simulator model, which essentially encodes the (quantum deformed) SU(2) Racah--Wigner tensor algebra, is particularly suitable to address problems arising in low dimensional topology and group theory. In this combinatorial framework we implement families of finite--states and discrete--time quantum automata capable of accepting the language generated by the braid group, and whose transition amplitudes are colored Jones polynomials. The automaton calculation of the polynomial of (the plat closure of) a link L on 2N strands at any fixed root of unity is shown to be bounded from above by a linear function of the number of crossings of the link, on the one hand, and polynomially bounded in terms of the braid index 2N, on the other. The growth rate of the time complexity function in terms of the integer k appearing in the root of unity q can be estimated to be (polynomially) bounded by resorting to the field theoretical background given by the Chern-Simons theory.

Spin Networks, Quantum Topology and Quantum Computation

Lecture Notes in Computer Science, 2007

We review the q-deformed spin network approach to Topological Quantum Field Theory and apply these methods to produce unitary representations of the braid groups that are dense in the unitary groups. The simplest case of these models is the Fibonacci model, itself universal for quantum computation. We here formulate these braid group representations in a form suitable for computation and algebraic work.

Spin networks and anyonic topological computing II

Proceedings of SPIE, 2007

We review the q-deformed spin network approach to Topological Quantum Field Theory and apply these methods to produce unitary representations of the braid groups that are dense in the unitary groups. The simplest case of these models is the Fibonacci model, itself universal for quantum computation. We here formulate these braid group representations in a form suitable for computation and algebraic work.

q-DEFORMED SPIN NETWORKS, KNOT POLYNOMIALS AND ANYONIC TOPOLOGICAL QUANTUM COMPUTATION

Journal of Knot Theory and Its Ramifications, 2007

We review the q-deformed spin network approach to Topological Quantum Field Theory and apply these methods to produce unitary representations of the braid groups that are dense in the unitary groups. Our methods are rooted in the bracket state sum model for the Jones polynomial. We give our results for a large class of representations based on values for the bracket polynomial that are roots of unity. We make a separate and self-contained study of the quantum universal Fibonacci model in this framework. We apply our results to give quantum algorithms for the computation of the colored Jones polynomials for knots and links, and the Witten-Reshetikhin-Turaev invariant of three manifolds.

BRAIDING AND ENTANGLEMENT IN SPIN NETWORKS: A COMBINATORIAL APPROACH TO TOPOLOGICAL PHASES

International Journal of Quantum Information, 2009

The spin network quantum simulator relies on the su(2) representation ring (or its q-deformed counterpart at q = root of unity) and its basic features naturally include (multipartite) entanglement and braiding. In particular, q-deformed spin network automata are able to perform efficiently approximate calculations of topological invarians of knots and 3-manifolds. The same algebraic background is shared by 2D lattice models supporting topological phases of matter that have recently gained much interest in condensed matter physics. These developments are motivated by the possibility to store quantum information fault-tolerantly in a physical system supporting fractional statistics since a part of the associated Hilbert space is insensitive to local perturbations. Most of currently addressed approaches are framed within a 'double' quantum Chern-Simons field theory, whose quantum amplitudes represent evolution histories of local lattice degrees of freedom.

SPIN NETWORK SETTING OF TOPOLOGICAL QUANTUM COMPUTATION

International Journal of Quantum Information, 2005

The spin network simulator model represents a bridge between (generalised) circuit schemes for standard quantum computation and approaches based on notions from Topological Quantum Field Theories (TQFTs). The key tool is provided by the fiber space structure underlying the model which exhibits combinatorial properties closely related to SU (2) state sum models, widely employed in discretizing TQFTs and quantum gravity in low spacetime dimensions.

Systematic Computation of Braid Generator Matrix in Topological Quantum Computing

arXiv (Cornell University), 2023

We present a systematic numerical method to compute the elementary braiding operations for topological quantum computation (TQC). Braiding non-Abelian anyons is a crucial technique in TQC, offering a topologically protected implementation of quantum gates. However, obtaining matrix representations for braid generators can be challenging, especially for systems with numerous anyons or complex fusion patterns. Our proposed method addresses this challenge, allowing for the inclusion of an arbitrary number of anyons per qubit or qudit. This approach serves as a fundamental component in a general topological quantum circuit simulator, facilitating the exploration and analysis of intricate quantum circuits within the TQC framework. We have implemented and tested the method using algebraic conditions. Furthermore, we provide a proof of concept by successfully reproducing the CNOT gate.

Spin networks and anyonic topological computing

SPIE Proceedings, 2006

We review the q-deformed spin network approach to Topological Quantum Field Theory and apply these methods to produce unitary representations of the braid groups that are dense in the unitary groups.