Cooperative States of Nd3+ Ion Pairs and Clusters in Nd3+:LaF3 Crystal

Up to now, only quantum computing using few quantum bits have been realized [1]. Main obstacles to increase the size of quantum register are fast decoherence and difficulties to control many-qubits entanglement. The clusters of the Nd
³⁺
ions formed in the Nd
³⁺
:LaF
³
crystal can be a candidate for many-qubit CNOT-gate, because of their entangled states due to strong coherent interaction (Davydov's splitting; bright and dark states with their own lifetimes τ and ra), weak electron-phonon coupling and long coherence time of the excited states. It was shown earlier that satellite lines of the main spectral line for single-site optical center of absorption [2, 3] and fluorescence excitation spectra [2] of Nd
³⁺
:LaF
³
crystals can be attributed to Nd
³⁺
ion pairs. The direct measurement of the fluorescence decay times for various classes of Nd
³⁺
pairs was made [2] since the pairs are well selected by fluorescence excitation wavelength.