We present a quantum repeater architecture using nitrogen-vacancy (NV) diamond based quantum information devices. The NV-diamond based device consists of a single negatively charged NV (NV<sup>-</sup>) center and an optical cavity. The electron of the NV center is an interface to light to be used to distribute long-distance entanglement as well as entanglement bonds for cluster state operation at each nodes. The nuclear spin-1=2 of nitrogen 15 can be used as memory. Based on this device, A scheme with as small as 10 devices to a scalable architecture is constructed, showing the necessary node technology as well as the performance such quantum communication systems.
Until recently, it was believed that long-lived quantum memories were necessary for long-distance quantum communication. However, by using error-correction codes in an efficient way—specifically, by correcting for photon loss—it is possible to transmit quantum information over long distances without quantum memories. For quantum computation, recent architectures for topological quantum computation indicate that the simplest large-scale structure could be memory-less. While a quantum memory may no longer be an essential resource for quantum networks, it could nonetheless be a key device in the development of quantum information technology. However, it is still not clear what benefits a functioning device could bring to quantum information systems, largely due to a lack of detailed models. Recently we have developed a detailed model for a quantum network based on a simple device designed to act as a building block for a full system architecture. The device is based on an optical cavity containing a negatively charged nitrogen-vacancy center in diamond. This model naturally integrates quantum communication with computation, and using this model we can assess quantitatively the costs and benefits of quantum memories. With or without quantum memories, it is necessary for us to preserve quantum information for a long period of time in either communication or computation.
In the paper we will discuss the design of a long range quantum repeater network and the components required
to realize it. We being by first reviewing the general approaches taken for distributing entanglement over long
ranges and identify general limitations caused by such approaches. We present a new entanglement generation
scheme that permits the near deterministic establishment of entangled links between nearest neighbor repeater
nodes and can be used to construct an arbitrary topology quantum network. The creation rate is shown at worst
to be a function of the maximum distance between any two adjacent quantum repeaters rather than of the entire
length of the network.
In this paper we provide a review of the perpetual optical topological quantum computer, a large scale quantum
architecture utilising a single quantum component. We will examine the building block of this architecture, the
photonic module, the original architecture design and a modified design which allows for the entire computer to
be constructed solely from a single component. Given the extraordinary specificity of this design we can provide
a pessimistic resource analysis, utilising deliberately bad circuit designs and arrangements to determine the size
and speed of a large scale factoring engine.
The publication in 1994 of Shor's algorithm, which allows factorization of composite number <i>N</i> in a time polynomial in its binary length <i>L</i> has been the primary catalyst for the race to construct a functional quantum computer. However, it seems clear that any practical system that may be developed will not be able to perform completely error free quantum gate operations or shield even idle qubits from inevitable error effects. Hence, the practicality of quantum algorithms needs to be investigated to estimate what demands must be made of quantum error correction (QEC). Several different quantum circuits implementing the quantum period finding (QPF) subroutine, which lies at the heart of Shor's algorithm have been designed, but each tacitly assumes that arbitrary pairs of qubits can be interacted. While some architectures posses this property, many promising proposals are best suited to realizing a single line of qubits with nearest neighbor interactions only. This paper will present a circuit suitable for implementing the QPF subroutine for such linear nearest neighbor (LNN) designs. We will then present direct simulation results showing for both the LNN circuit and for a circuit utilizing arbitrary interactions, that the QPF subroutine is very sensitive to a small number of errors in the entire circuit. These results can then be used to briefly examine some of the practical issues to implementing such large scale quantum algorithms.
We construct fault-tolerant approximations of rotation gates
required by Shor's algorithm using only fault-tolerant gates that
can be applied to the 7-qubit Steane code. A general scaling law
of how rapidly these fault-tolerant approximations converge to
arbitrary single-qubit gates is also determined.