Abstract
The possibility of observing spontaneous parametric down-conversion in doped nonlinear crystals at low temperatures, which would be useful for combining heralded single-photon sources and quantum memories, is studied theoretically. The ordinary refractive index of a lithium niobate crystal doped with magnesium oxide LiNbO 3 :MgO is measured at liquid nitrogen and helium temperatures. On the basis of the experimental data, the coefficients of the Sellmeier equation are determined for the temperatures from 5 to 300 K. In addition, a poling period of the nonlinear crystal has been calculated for observing type-0 spontaneous parametric down-conversion (ooo-synchronism) at the liquid helium temperature under pumping at the wavelength of λ p = 532 nm and emission of the signal field at the wavelength of λ s = 794 nm, which corresponds to the resonant absorption line of Tm 3+ doped ions.
Highlights
Spontaneous parametric down-conversion (SPDC) is the most common way of generating non-classical states of the electromagnetic field, in particular single-photon or two-photon states [1, 2]. When such states are used in the systems of long-distance quantum communications or quantum computing, it may be useful to have the possibility to store them in a quantum memory device immediately after their generation
Even temperature dependence of refractive indices of nonlinear crystals that could be used for combining single-photon sources and quantum memories has not been investigated at low temperatures
In the pre-sent work, we study the possibility of observing SPDC at low temperatures in such nonlinear crystals
Summary
Spontaneous parametric down-conversion (SPDC) is the most common way of generating non-classical states of the electromagnetic field, in particular single-photon or two-photon states [1, 2]. When such states are used in the systems of long-distance quantum communications or quantum computing, it may be useful to have the possibility to store them in a quantum memory device immediately after their generation. The optimal solution might be the combination of the SPDC-based photon source and quantum memory in a single system utilizing a doped nonlinear crystal as an information carrier.
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