SFB / TRR 21 Control of Quantum Correlations in Tailored Matter

Project C4 Correlated quantum states in defect centre clusters

Summary

Defects centers in diamond show well controllable magnetic and optical properties. Also their position within the bulk can be controlled with good accuracy. The chosen nitrogen vacancy defect center has an optically accessible paramagnetic ground spin state spin. Within the project clusters of closely spaced defect centers should be fabricated. Owing to their long coherence times the optical transition - as well as magnetic dipole moment- allows to create correlated quantum states throughout a cluster of defect centers. The project is aimed at maximizing and investigating the achievable correlation by tailoring cooperative quantum states. This can for example been done by creating a multi quantum optical as well as magnetic resonance coherence. In the cluster the optical dipole as well as magnetic dipole transition can be tuned with respect to each other. This may be used to simulate quantum phase transitions within the ensemble. Further on the interaction between the system and a spin bath can be controlled. The dephasing properties of cluster states can thus be investigated for different coupling strength. In the second part of the project polariton states, i.e. coupled light matter states should be generated by using light pulses and the spin ground state of the defect centers. It is the aim to achieve a complete and reversible mapping of light states onto the spin states of an ensemble of defect center spins. We intend to test theoretical models which predict slow decoherence of the resulting multiparticle spin states. In the third part of the project the coupling of the light field to internal degrees of freedom of the defect centers should used to generate slow group velocities of a probe light field. This should be achieved by using coherent population oscillations between the defect center ground state and its first excited state. It should be inquired whether the group velocity of a probe light field can be controlled via an external parameter yielding a switchable group velocity device which might work under ambient conditions.

Project leaders

Prof. Dr. Fedor Jelezko, Institut für Quantenoptik, Universität Ulm

Prof. Dr. Jörg Wrachtrup, 3. Physikalisches Institut, Universität Stuttgart