Interfacing External Quantum Devices to a Universal Quantum Computer

We present a scheme to use external quantum devices using the universal quantum computer previously constructed. We thereby show how the universal quantum computer can utilize networked quantum information resources to carry out local computations. Such information may come from specialized quantum devices or even from remote universal quantum computers. We show how to accomplish this by devising universal quantum computer programs that implement well known oracle based quantum algorithms, namely the Deutsch, Deutsch-Jozsa, and the Grover algorithms using external black-box quantum oracle devices. In the process, we demonstrate a method to map existing quantum algorithms onto the universal quantum computer

A Precise Error Bound for Quantum Phase Estimation

Quantum phase estimation is one of the key algorithms in the field of quantum computing, but up until now, only approximate expressions have been derived for the probability of error. We revisit these derivations, and find that by ensuring symmetry in the error definitions, an exact formula can be found. This new approach may also have value in solving other related problems in quantum computing, where an expected error is calculated. Expressions for two special cases of the formula are also developed, in the limit as the number of qubits in the quantum computer approaches infinity and in the limit as the extra added qubits to improve reliability goes to infinity. It is found that this formula is useful in validating computer simulations of the phase estimation procedure and in avoiding the overestimation of the number of qubits required in order to achieve a given reliability. This formula thus brings improved precision in the design of quantum computers.Comment: 6 page

Analytic theory of two wave interactions in a waveguide with a χ(3) nonlinearity

In a material with a Kerr nonlinearity such as glass it is possible to generate the third harmonic of an incident wave, however in general, due to material dispersion such a process is not phase-matched and so rarely occurs with any useful efficiency. The theory of third harmonic generation thus remained a theoretical curiousity which meant that the work of Armstrong et al. [1] who found an analytic solution to the problem (which was further extended by Puell and Vidal [2]) has been forgotten resulting in later authors having to re-derive similar solutions [3]

Instruction Set.

<p> Instruction Set.</p

Defining the limits of summation for the phase estimation error.

<p>For the cases , we show the measurements which are accepted as lying within the required distance of , shown by the vertical arrow, which define the limits of summation used in Eq. (13).</p