The architecture scalability afforded by recent proposals of a large scale photonic based quantum computer, utilizing the theoretical developments of topological cluster states and the photonic chip, allows us to move on to a discussion of massively scaled Quantum Information Processing (QIP). In this letter we introduce the model for a secure and unsecured topological cluster mainframe. We consider the quantum analogue of High Performance Computing, where a dedicated server farm is utilized by many users to run algorithms and share quantum data. The scaling structure of photonics based topological cluster computing leads to an attractive future for server based QIP, where dedicated mainframes can be constructed and/or expanded to serve an increasingly hungry user base with the ideal resource for individual quantum information processing. Since the introduction of quantum information science in the late 1970's and early 1980's, a large scale physical device capable of high fidelity quantum information processing (QIP) has been a major and highly sought after goal. While quantum information has lead to many extraordinary developments in foundational quantum theory, quantum atom/optics, solid state physics and optics many researchers world wide are still striving towards a physical quantum computer. The issue of computational scalability for QIP has been an intensive area of research for not only physicists but also computer scientists, mathematicians and network analysis and in the past decade has seen many proposals for scalable quantum devices for a variety of quantum architectures [1] . The complexity in designing a large scale quantum computer is immense and research in this area must incorporate complex ideas in theoretical and experimental physics, information theory, quantum error correction, quantum algorithms and network design. Due to the relative infancy of theoretical and experimental QIP it has been difficult to implement theoretically scalable ideas in quantum information theory, error correction and algorithm design into an architectural model where the transition from 1-100 qubits to 1-100 million qubits is conceptually straightforward. Recent theoretical advancements in computational models for QIP has introduced an extremely elegant pathway to realize a enormously large QIP system in optics. Topological cluster state computing, first introduced by Raussendorf, Harrington and Goyal [2] has emerged as an extremely promising computational model for QIP and integration of this model with chip-based photon/photon gates such as the photonic module has lead to a promising optical realization of quantum computation [3, 4] . The conceptual scalability of the chip based topological optical computer allows, for the first time, a grounded discussion on large scale quantum information processing, beyond the individual computer. In this letter we take the scalability issue one step further, examining the possible long term implementation of topological cluster state computing with the photonic chip and discuss what the future may hold for this architectural model of QIP. Traditional discussions of scalability in QIP is generally limited to the issue of constructing a single, moderately large scale quantum computer, capable of performing non-trivial algorithms for a single user. In the case of topological cluster state computation in optics we can consider the possibility of client/mainframe quantum devices and start to consider the quantum analogue of classical high performance computing, namely High Performance Quantum Computing (HPQC) where a large, generic quantum resource is made available to multiple clients to perform independent (or joint) QIP. Topological cluster state computing in optics is uniquely suited to this task for several reasons. Aside from the error correcting and resource benefits of the topological cluster model, the basic geometric structure of the lattice allows for multi-user computation that would be problematic when utilizing the more traditional 2D cluster state techniques [5] . In traditional 2D cluster state computing, multiple users could not interact data with each other or with a central resource core without transporting quantum information through the cluster resource of other users. Essentially multi-user interactions would be a Linear Nearest Neighbor (LNN) network. Moving to 3D topological clusters convert this LNN network topology into a 2D grid, enabling the partitioning of the cluster lattice into user regions and resource regions. Additionally, as the lattice is carried by single photons we can potentially integrate a mainframe model with developments in quantum communications and entanglement distribution [6] . This gives a layer of security to the HPQC which would be difficult, if not impossible to achieve for multi-user, matter based qubit architectures. Here we introduce the basic framework for a potential HPQC based on topological cluster state computing in the photonic regime [ Fig. 1] . We discuss two possible mainframe models, one where multi-user computation is arXiv:0810.2444v1 [quant-ph]
Devitt et al. integrated the topological quantum model with the photonic module to build a photonic topological quantum network over different areas REF .
High Performance Quantum Computing
Progress in Informatics 8 (2011): 49-55
Physics Computer Science Mathematics