Applied Physics Seminar

In this talk I will cover some of the applications of cryogenic rare earths that we are investigating at Otago.

1) Rephased amplified spontaneous emission (RASE) results from using rephasing pulses to get and 'echo' of the amplified spontaneous emission (ASE) produced. Important for quantum information applications the ASE and it's echo are entangled. So far experiments that we and others have carried out have been able to show correlation but not, definitively, entanglement. I will outline theory showing that the quality of the entanglement can be increased with a resonator and the perfect entanglement is in principle possible if the atom-cavity interaction can be modulated somehow dynamically (tuning, Q-switching )

2) Using rare earth based filters for ultrasound modulated optical tomography (UMOT). UMOT requires that sideband light, produced by
ultrasound, be separated from the unshifted carrier light. This is challenging because both light fields are highly scattered and the frequency shifts (given by the ultrasound frequencies) are small. We chose to tackle this problem using filters borrowed from research into
optical quantum memories. With this we showed a record selectivity between carrier and side band light. I will also show our first imaging
efforts.

3) Upconverting microwave to optical photons. Superconducting qubits are exciting systems for quantum information. However the microwave photons that they couple to get swamped by thermal noise unless at milli-Kelvin temperatures. Converting microwave photons to optical photons in a way that preserves the encoded quantum states would solve this problem. I will outline our proposal for achieving this conversion using rare earth ion dopants and present some experimental results demonstrating low efficiency upconversion.