Abstract

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 Nd³⁺ ions formed in the Nd³⁺:LaF₃ 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 τb and τd), 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 Nd³⁺:LaF₃ crystals can be attributed to Nd³⁺ ion pairs. The direct measurement of the fluorescence decay times for various classes of Nd³⁺ pairs was made [2] since the pairs are well selected by fluorescence excitation wavelength.

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