Participants:
Nicolas Godbout, Thomas Jennewein, Kevin Resch, Aephraim Steinberg, Wolfgang Tittel, Gregor Weihs, Robin Williams.
Partners:
National Research Council, Nortel Networks.
Optical quantum communication and quantum computation are promising but place stringent demands on sources, transmission and detection of light. In particular single photon sources and sources of correlated photons in the optical and infrared domains are important, as are detectors in those spectral domains that count photons and discriminate between one, two, and more photons at a time.
The range of photonic quantum information is limited by the quality of carriers, such as the atmosphere or optical fibres, hence also of critical concern. This project seeks to deliver excellent singlephoton and correlated photon sources, discriminating photon counters, and high-quality longdistance carriers.
Practical optical quantum information processing requires sources of identical, highefficiency, Fourier-limited single photons produced with a high repetition rate. Depending on the application, infrared or optical photons are needed. We will develop single-photon sources by constructing quantum dot nanostructures, with the goal of producing infrared (1550nm) single photons. Quantum dot sources appear to be the most promising stable, high-efficiency, Fourierlimited sources of single photons.
Another key effort will be the development of entangled-photon generators via parametric down conversion both in crystals and in optical fibres via four-wave mixing. Whereas parametric down conversion in crystals is well-developed, and we will use these sources to produce highorder multiphoton entangled states, the optical fibre source is in its infancy, but, if successful, would yield a compact, low-cost, tunable, turnkey source of entangled photons that would be ideally suited for propagation in fibres.
Building on recent work where some of us have experimentally demonstrated a potentially scalable technique for generating maximally path-entangled states of more than two photons, we will pursue this effect, as an appropriate path towards generation of larger-scale optical entanglement. This project will collaborate with the project to develop reliable single-photon sources in B3, as well as through improvements on our ultrafast entangled-state sources.
Figure 6: Photonic bandgap membrane structure tailored to the characterised emission of a selected dot to electronically gate individual, site selected quantum dots and embed them within high finesse microcavities.
Finally we will investigate entangled photons generated through parametric down-conversion in second-order nonlinear optical crystals. Entangled pairs can also be generated using fourwave mixing in optical fibre, a third-order nonlinear effect. The anticipated design will be based on vectorial modulation instability in birefringent optical fibres which enables simple tuning of the photons wavelength. The goal of this activity is to design and fabricate complete entangled photon sources in a single box. This box will include a pulsed fibre laser, nonlinear optical fibre for the generation of photons and high-quality filters to separate the generated photons from the intense pump laser light. This will result in a compact, low-cost, tunable, turn-key optical fibre sources of entangled photon pairs which can be sent to other Network members for integration in other experiments.
This project will interact with project QB5 on benchmarking and on QC1 on quantum cryptographic prototypes. Nortel Networks has shown interest in this research and we are interacting with them for financial commitments and Cyrium Technologies will collaborate with Dr Williams.