New form of photon-based quantum computation realized

Ahmed El-Halawany, Michael Leuenberger

Xiaoqin Gao, Zhengwei Liu

We use one photon to simulate an n-qubit quantum system for the first time. We propose a new scheme to realize universal quantum computation in polynomial time O(n^5). A generating set of gates can be realized with high accuracy in the lab. We conclude that photonic quantum computation is one of the promising approaches to universal quantum computation.

Takaaki Musha

On the basis of a theorem, in which an evanescent photon is a superluminal particle, the author considers the possibility of realizing a high performance computer system compared with conventional silicon processors. To realize such a quantum computer utilizing evanescent photons, we must replace electronic components with optical ones, and thus an equivalent optical transistor is required. This critical component for quantum computing can be created using meta-material circuits with a non-linear refractive index. Based on this optical computer system, utilizing metamaterial technology, it can be shown that superluminal computation, which is a new concept for hypercomputation, can be realized in the physical world.

Christophe Couteau

K. V. Bayandin, Gordey B. Lesovik

We propose a new cryptographic protocol. It is suggested to encode information in ordinary binary form into many-qubit entangled states with the help of a quantum computer. A state of qubits (realized, e.g., with photons) is transmitted through a quantum channel to the addressee, who applies a quantum computer tuned to realize the inverse unitary-transformation decoding of the message. Different ways of eavesdropping are considered, and an estimate of the time needed for determining the secret unitary transformation is given. It is shown that using even small quantum computers can serve as a basis for very efficient cryptographic protocols. For a suggested cryptographic protocol, the time scale on which communication can be considered secure is exponential in the number of qubits in the entangled states and in the number of gates used to construct the quantum network.

Jeremy L. O’Brien

Quantum computation with photons