Optimised control of Stark-shift-chirped rapid-adiabatic-passage in a lambda-type three-level system

Inhomogeneous broadening of energy levels is one of the principal limiting factors for achieving "slow" or "stationary" light in solid state media by means of electromagnetically induced transparency (EIT), a quantum version of stimulated Raman adiabatic passage (STIRAP). Stark-shift-chirped rapid-adiabatic-passage (SCRAP) has been shown to be far less sensitive to inhomogeneous broadening than STIRAP, a population transfer technique to which it is closely related. We further optimise the pulses used in SCRAP to be even less sensitive to inhomogeneous broadening in a lambda-type three-level system. The optimised pulses perform at a higher fidelity than the standard gaussian pulses for a wide range of detunings (i.e. large inhomogeneous broadening).Comment: 6 pages, 6 figures, 1 tabl

Control and engineering of optical nonlinearities in multi-level quantum systems

Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics and Astronomy, 2011.Bibliography: p. 87-99.1. Introduction -- 2. EIT, STIRAP and NV centre as a Λ-type three level system -- 3. Optimised Stark-shift-chirped rapid adiabatic passage -- 4. Quantum phase gate schemes -- 5. NV center Four-level Tripod Quantum Phase Gate -- 6. Breeding Schrödinger cats with diamonds -- 7. Conclusion -- A. Appendix.We investigate methods related to achieving interaction between photonic qubits. The first general approach to achieve this is to transfer photonic qubits to solid state systems, where the qubit interactions can then take place. The other approach is to enhance the strength of the photon-photon interaction. -- We first robustly study methods related to the first approach: in particular we focus on how to convert the photonic quantised excitation into an atomic excitation. The Stark-shift-chirped rapid adiabatic passage (SCRAP) technique in a three level Λ-type system is a coherent population transfer (CPT) technique similar to Stimulated Raman Adiabatic Passage (STIRAP), which in itself is closely related to electro-magnetically induced transparency (EIT). SCRAP has been shown to perform CPT with a high delity for a range of different detunings making SCRAP far more robust when there is large inhomogeneous broadenings present in the ensemble. We make use of optimum control techniques in order to optimise the standard SCRAP pulses so as to minimise the decrease in delity brought on by inhomogeneous broadenings of the transitions. Our result is that we can improve the average delity of population transfer over a wide range of detunings for both the ground to excited state detuning and the ground to target state detuning (two-photon detuning). -- Finally we consider the enhancement of photon-photon interactions and the implementation of an optical quantum controlled not (CNOT) gate via a cavity-QED setup. We explore the Nitrogen-vacancy centre in diamond as a suitable four-level tripod system in which to generate the cross-Kerr nonlinearity required to facilitate the strong interaction between the two fields (control and target) held in a cavity. We show that with an ultra-high quality factor cavity, and only a single NV centre strongly coupled to the trapped light, a suffciently large interaction can be generated between the two fields to obtain a conditional phase shift (CPS) in excess of the required π for the successful implementation of a CNOT gate. We also show that it is possible to use this system to create an entangled state of two macroscopically distinguishable states, that is a Schrödinger cat state, by using two weak coherent fields as input and making a measurement on the second field.Mode of access: World Wide Web.1 online resource (xx, 99 p.) ill. (some col.