A. A. Kalachev

Cavity-assisted atomic frequency comb memory in an isotopically pure 143Nd3+ :YLiF4 crystal

In this work we present an implementation of cavity-assisted atomic frequency comb (AFC) memory protocol in an isotopically pure 143Nd3+ :YLiF4 crystal. We use a tunable confocal Fabry–Perot cavity that is placed inside the cryostat. For a 1 mm thick sample with optical depth of 0.2 we obtain total storage efficiency of 3%, which is a 15-fold enhancement compared to the no cavity case. The memory bandwidth is limited by the inhomogeneous broadening of the optical transition and allows us to store short 30 ns pulses.

Atomic frequency comb memory in an isotopically pure 143Nd3+:Y7LiF4 crystal

We implemented the atomic frequency comb protocol for optical quantum memory in an isotopically pure crystal of Y7LiF4 doped by 143Nd3+ ions. Echo signals were observed on the 4I9/2(1)–4F3/2(1) transition, which had inhomogeneous broadening much smaller than the hyperfine splitting of the ground and excited states. We performed hole-burning spectroscopy measurements on several transitions, obtaining information about the hyperfine state lifetimes. An intrinsic hole structure was found on some of the transitions, which allowed us to prepare a comb structure with two clearly defined periods and to observe echo pulses with different time delays.

Multichannel information processing in the optical echo-processors on the basis of Van-Fleck paramagnet crystals

The analysis of various modes of multichannel information recording and readout in conditions of a stimulated (accumulated and long-living) photon echo in the crystals doped with rare earth ions which are known as Van-Fleck paramagnets has been performed in order to utilize them in the operation of low-temperature optical echo-processors.

Writing and reading quantum states of light with tunable cavity: Application to single-photon sources

A method of writing and reading single-photon states of light in quantum memory devices whose information carriers are optically thin resonant media placed in a cavity is developed. It is shown that, using a tunable cavity, it is possible to write and reproduce Gaussian single-photon wave packets with an efficiency close to unity. The possibility of using this method for the transformation of the time shape of single photons generated in the cavity-enhanced spontaneous parametric down conversion regime is analyzed.

Multipulse regimes of excitation of optical superradiance due to a two-photon transition

Multimode triggered optical superradiance due to a two-photon transition is theoretically studied. Kinetic equations are derived for the dynamics of cooperative development of coherence and population inversion of optical centers interacting with each other through a common field of emitted photons. Various regimes of triggering of optical superradiance due to a two-photon transition are considered. The possibility of creating a quantum photomultiplier on the basis of the triggered optical superradiance is discussed.

Multipulse excitation of optical superradiance in multilevel systems

The multipulse regime of excitation of optical superradiance in both two- and multilevel systems is theoretically investigated. It is demonstrated that this regime is the generalization of the triggering regime of superradiance excitation. The possibilities of information processing and laser cooling of solids under this superradiant regime are discussed.

Third-order spontaneous parametric down-conversion in a ring microcavity

The theory of third-order spontaneous parametric down-conversion (TOSPDC) in a ring waveguide microcavity is developed. Analytical expressions for the rate of photon triplet emission are presented for both the monochromatic-pump and pulsed-pump regimes. In the latter case, rising exponential pulses are considered as optimal ones for the cavity excitation. It is demonstrated by numerical simulations that a silicon-nitride based ring microcavity can be a promising system for developing narrowband sources of photon triplets based on TOSPDC.

Generation of pure single-photon states via spontaneous four-wave mixing in nanofibers with a variable cross section

A theory of single-photon sources of light is developed on the basis of spontaneous four-wave mixing in optical nanofibers. The spectral amplitude of the biphoton field is calculated with allowance for the real geometry of a nanofiber manufactured from standard optical fiber by heating and stretching. It is shown that by selecting pump parameters, we can simultaneously obtain the high spectral brightness and low frequency correlation of generated biphoton states in a nondegenerate mode of four-wave mixing that corresponds to single-photon states with the high purity.

Polarization tomography of a narrow-band biphoton field

Narrow-band orthogonally polarized collinear frequency-degenerate biphotons are generated in the process of the spontaneous parametric down-conversion of light in a nonlinear BBO crystal placed in an optical resonator. Quantum polarization tomography and polarization transformation of the generated biphoton states are performed. The results from our experiment agree well with theoretical calculations.

Transformation of single-photon wave packets in quantum storage with a tunable cavity

Optimal conditions for transformation of the waveform of single photons generated via cavity-enhanced spontaneous parametric down-conversion by means of optical quantum storage, in which an extended resonant medium in a tunable cavity is used as information carrier, are determined.