Experimental linear optical logic
Seminar Room 1, Newton Institute
Coding data bits in the phase or polarisation state of single photons allows us to exploit wave particle duality for novel communication protocols. Fibre and free-space quantum cryptography apparatus used for secure exchange of keys exploit this discovery [1,2]. Key sharing schemes are easily realised because they involve only single qubit manipulation. Further developments such as quantum relays and other few qubit applications require that pairs of qubits interact. To avoid the inevitably weak non-linear interactions between photons conditional linear optics logic has been developed to demonstrate CNOT operation albeit with limited efficiency [3,4]. We are developing suitable single photon and pair photon sources in order to demonstrate a teleportation based scalable CNOT gate. Key aims are to demonstrate efficient sources and optical circuits with high success probability. We also aim to exploit the low decoherence of photons to demonstrate high fidelity (QBER <10-4) operation. The presentation will summarise our progress towards these aims.  N. Gisin, G. Ribordy, W. Tittel and H. Zbinden Rev. Mod. Phys. 74, 145 (2002).  C. Kurtsiefer, et al, Nature 419, 450 (2002).  J.G.Rarity, Roy. Soc. Phil. Trans. 361, 2003, 1507-18  J.L. O'Brien et al, Nature 426, 264 (2003).