**Characterizing single photon devices for quantum information applications** - Chris O'Brien

New advances in quantum information processing will require the successful construction
of single photon devices such as optical quantum memories and single photon frequency
converters. Having good theoretical models for the operation and noise characteristics of these devices are essential to their successful construction.
I will discuss two single photon devices. First, I will show how non-linear processes such as four-wave mixing introduce noise into optical quantum memories, in particular in electromagnetically induced transparency based quantum memories. Where we have shown [1] that noise due to non-linear mixing is the dominant term to the reduction of single photon storage fidelities. Understanding this noise, can lead to the creation of higher fidelity optical quantum memories.
Second, I will consider schemes for coupling superconducting quantum circuits, which show promise for scalable quantum computation, to telecom wavelength photons which are compatible with low loss optical fibers. Essentially converting a qubit from optical frequencies to a microwave excitation. This is accomplished by storing telecom photons as collective spin excitations in a rare-earth doped crystal, which are then coupled to the qubit by a microwave stripline resonator [2].
[1] N. Lauk, C. O'Brien, M. Fleischhauer, Phys. Rev. A 88, 013823 (2013).
[2] C. O'Brien, N. Lauk, S. Blum, G. Morigi, M. Fleischhauer, arXiv: 1402.5405 (2014).