Method of extending hyperfine coherence times in Pr^3+:Y_2SiO_5

摘要

In this letter we present a method for increasing the coherence time ofpraseodymium hyperfine ground state transitions in Pr^3+:Y_2SiO_5 by theapplication of a specific external magnetic field. The magnitude and angle ofthe external field is applied such that the Zeeman splitting of a hyperfinetransition is at a critical point in three dimensions, making the first orderZeeman shift vanishingly small for the transition. This reduces the influenceof the magnetic interactions between the praseodymium ions and the spins in thehost lattice on the transition frequency. Using this method a phase memory timeof 82ms was observed, a value two orders of magnitude greater than previouslyreported. It is shown that the residual dephasing is amenable quantum errorcorrection.