Small quantum circuits for optical quantum computing

Mark G. Thompson, A Politi, JCF Matthews +1 more

David Peter Divincenzo

Christoph Adami, Nicolas J. Cerf

We present a constructive method to translate small quantum circuits into their optical analogues, using linear components of present-day quantum optics technology only. These optical circuits perform precisely the computation that the quantum circuits are designed for, and can thus be used to test the performance of quantum algorithms. The method relies on the representation of several quantum bits by a single photon, and on the implementation of universal quantum gates using simple optical components (beam splitters, phase shifters, etc.). The optical implementation of Brassard et al.'s teleportation circuit, a non-trivial 3-bit quantum computation, is presented as an illustration.

Sverre Gullikstad Johnsen

Dmytro O. Kundys, James C. Gates, Corin B. E. Gawith +4 more

Integrated planar lightwave circuits (PLCs) provide a promising route to small-scale quantum optical networks [1]. Recent work on quantum logic gates using silica-based PLCs has highlighted the opportunities afforded by the ability to coherently manipulate degrees of freedom at the level of single photons [2]. Increasingly complex waveguide networks are required for linear optics quantum computing (LOQC), a route towards small scale quantum information processing [3]. This approach uses quantum interference between photons and measurements with feedforward to implement the nonlinear interactions between photons that are required for information processing. A major issue in developing such circuits is the internal loss and the coupling efficiency of input photon from optical fibers.

Hiroyuki Okada

In order to realize the ultimate goal of developing universal photon quantum circuits using liquid crystals, we have numerically analyzed the transmission and reflection of photons in a 4× 4 matrix method for an optical switching device, and clarified the possibility of applying interference light to quantum circuits. The results showed that switching between reflection and entangled states was possible at an incident angle of 86° with homogeneous orientation and HOM interference condition. Very small amplitude of photon analysis was also carried out to analyze the symmetry of the properties based on the uncertainty quantities.