arXiv subjects

Robert T. Thew

Publications and source records attributed to Robert T. Thew.

3 recordsLinked to original sources

arXiv2014

Pulsed source of spectrally uncorrelated and indistinguishable photons at telecom wavelengths

We report on the generation of indistinguishable photon pairs at telecom wavelengths based on a type-II parametric down conversion process in a periodically poled potassium titanyl phosphate (PPKTP) crystal. The phase matching, pump laser characteristics and coupling geometry are optimised to obtain spectrally uncorrelated photons with high coupling efficiencies. Four photons are generated by a counter- propagating pump in the same crystal and anlysed via two photon interference experiments between photons from each pair source as well as joint spectral and g^(2) measurements. We obtain a spectral purity of 0.91 and coupling efficiencies around 90% for all four photons without any filtering. These pure indistinguishable photon sources at telecom wavelengths are perfectly adapted for quantum network demonstrations and other multi-photon protocols.

quant-ph↗

arXiv2013

Interaction of Independent Single Photons based on Integrated Nonlinear Optics

Photons are ideal carriers of quantum information, as they can be easily created and can travel long distances without being affected by decoherence. For this reason, they are well suited for quantum communication. However, the interaction between single photons is negligible under most circumstances. Realising such an interaction is not only fundamentally fascinating but holds great potential for emerging technologies. It has recently been shown that even weak optical nonlinearities between single photons can be used to perform important quantum communication tasks more efficiently than methods based on linear optics, which have fundamental limitations. Nonlinear optical effects at single photon levels in atomic media have been studied and demonstrated but these are neither flexible nor compatible with quantum communication as they impose restrictions on photons' wavelengths and bandwidths. Here we use a high efficiency nonlinear waveguide to observe the sum-frequency generation between a single photon and a single-photon level coherent state from two independent sources. The use of an integrated, room-temperature device and telecom wavelengths makes this approach to photon-photon interaction well adapted to long distance quantum communication, moving quantum nonlinear optics one step further towards complex quantum networks and future applications such as device independent quantum key distribution.

quant-ph↗

arXiv2001

Universal quantum computation and simulation using any entangling Hamiltonian and local unitaries

What interactions are sufficient to simulate arbitrary quantum dynamics in a composite quantum system? We provide an efficient algorithm to simulate any desired two-body Hamiltonian evolution using any fixed two-body entangling n-qubit Hamiltonian and local unitaries. It follows that universal quantum computation can be performed using any entangling interaction and local unitary operations.

quant-ph↗