Quantum Technology

Spectroscopy of entangled states of clusters of rare-earth impurity ions for quantum computing.
We consider a problem of creation and control of cooperative quantum states, entangled states (such as Bell and Greenberger–Horne–Zeilinger states) in groups of closely-spaced rare-earth impurity ions (large clusters with many energy levels). Coherence preservation in Re3+ doped fluoride crystals at low temperature can be longer than characteristic nanosecond time of quantum CNOT gates, which is enough to perform algorithmic operations in quantum computers. We do site-selective spectroscopy of quantum states of clusters of Nd3+, Ho3+, Er3+ ions in fluoride crystals to reveal the dynamical splitting (no magnetic field) of Stark levels due to coherent interaction between the ions.