Spin-selective low temperature spectroscopy on single molecules with a triplet-triplet optical transition: Application to the NV defect center in diamond

Fault-tolerant quantum repeaters with minimal physical resources and implementations based on single-photon emitters

“…However, it can increase the time required for these operations. Fluorescence correlation experiments are consistent with assigning a metastable singlet structure to the shelving state, which is coupled strongly to the M s = ±1 excited states but only weakly to the M s = 0 excited state (see Figure 2), [24]. We need to account for the possibility that our NV center bleaches during entanglement generation, requiring us to start over.…”

“…As spin-orbit and spin-spin effects are substantially different for the optically excited state (E symmetry class), the strong transition from the M s = 0 sublevel of the ground orbital state can be excited independently of the other M s states. Although there is evidence for photo-bleaching at low temperatures, current models indicate that crossover into the dark metastable state occurs primarily from the M s = ±1 excited states [24]. Furthermore, crossover into the trapping state is a detectable error.…”

Nitrogen-vacancy center in diamond: Model of the electronic structure and associated dynamics

“…For completeness other transitions allowed in low symmetry are shown as dashed lines. The low symmetry situation is similar to that proposed by others [10,33,34] and to assist comparison we adopt their shortened notation. The ground spin states are defined as x, y and z; the excited triplet states as x', y' and z' and the singlet level as s. In the following experiments we determine the values of the parameters using bulk samples.…”

“…Wrachtrup and co-workers at University of Stuttgart and at the National Academy of Sciences of Belarus have presented an exciting range of single site measurements including demonstrating aspects of quantum computing [7,8,9,10,11,33,34,44,45]. In the model adopted to interpret their results they have spin as a good quantum number and spin-orbit interaction is neglected.…”

“…It is noted that the analysis of the photon statistics associated with emission from single N-V centers [2,3,4,5,33] has assumed that either there is significant singlet-triplet back transfer or a long lived singlet state (or both). Consequently the parameters reported are inconsistent with the values obtained here.…”