Multiresonator Quantum Memory with Single Atoms

M. M. Minnegaliev, K. I. Gerasimov, R. V. Urmancheev, A. M. Zheltikov, and S. A. Moiseev

JETP Letters. Т. 115. №. 6. С. 318-323 (2022)

DOI: 10.1134/S0021364022200255

Quantum memory based on a system of resonators each containing one atom and connected to an external waveguide through a common resonator has been proposed. The parameters of the resonators and atoms interacting with them at which the effective transfer of a single-photon signal wave packet from the external waveguide to atomic states for long-term storage of the quantum state of the photon have been determined using reversible properties of the dynamics of the system under study and optimization methods. The advantages of quantum memory under consideration, as well as experimental possibilities of its implementation, have been discussed.

Non-Adiabatic Fast Quantum Memory on an Atom-Resonator System Provided by Optimal Switching on a Control Field

Yu. A. Kharlamova, N. M. Arslanov & S. A. Moiseev

Bulletin of the Russian Academy of Sciences: Physics 86, 1507–1510 (2022)

DOI: 10.3103/S1062873822120139

The efficiency of non-adiabatic quantum memory based on the Raman interaction between a photon and a three-level atom in a high-Q resonator was investigated. The optimum gradual switch-on form of a control field ensures high efficiency of the fast quantum memory is found. Proposals for improving the basic parameters of the considered quantum memory using realistic experimental parameters are shortly discussed.

Optimizing the Parameters of a Periodically Poled LiNbO3 Nanowaveguide Structure for Generating Ultrabroadband Biphotons in the Near-IR Range

O. A. Ermishev, M. A. Smirnov, A. F. Khairullin & N. M. Arslanov

Bulletin of the Russian Academy of Sciences: Physics. 86, 1502–1506 (2022)

DOI: 10.3103/S1062873822120085

For quantum biomicroscopy, light sources need to provide a reliable signal at low intensity levels with a high rate generation in the near-infrared region. To develop this light source, we investigated the abilities of generating ultrabroadband two-photon states in the near-infrared in a periodically poled lithium niobate (LiNbO3) nanowaveguide with different geometrical cros-section and pump wavelength. Using modeling and numerical calculations the optimal nanowaveguide parameters providing the maximum width of the spectrum of two-photon states ~180 THz under the pump wavelength about 1.0 μm were determined.

Quantum memory on atomic frequency comb in a plasmon-polariton waveguide

N. M. Arslanov, S. A. Moiseev

Proc. SPIE 12157, International Conference on Micro- and Nano-Electronics 2021, 121572F (2022)

DOI: 10.1117/12.2625231

In this work, we present a nano-optical scheme of quantum memory for surface plasmon-polariton (SPP) modes in a nanoscale planar waveguide with a resonant atomic ensemble characterized by the periodic structure of the inhomogeneously broadened line. The theoretical study of the SPP modes is presented, where the regime of slow propagation and low-losses was found for these modes with fixed transverse spatial confinement, which provides a strong nondissipative interaction with resonant atoms. We describe the basic physical properties of the studied scheme and demonstrate a perspective area for the implementation of fast nanoscale quantum memory and processing with surface SPP modes.

Quantum transistor with multi-qubit memory in an integral waveguide-resonator scheme

N. M. Arslanov, S. N. Andrianov, Yu. A. Kharlamova, S. A. Moiseev

Proc. SPIE 12157, International Conference on Micro- and Nano-Electronics 2021, 121572E (2022)

DOI: 10.1117/12.2625224

In this work, we present an integrated waveguide-resonator scheme of an atomic quantum transistor with a multi-qubit memory. The quantum transistor is realized in an atomic-photon molecule formed of a linear chain of three interconnected resonators, each of which contains one resonant three-level atom. The resonators are connected through the waveguides to the quantum memory containing long-lived multi-atomic ensembles capable of storage of photonic qubits with an arbitrary temporal mode. We consider the protocols for implementation of one- and two-qubit operations in the proposed scheme over a system of qubits stored in quantum memory. The advantages and experimental implementation of the proposed scheme are also discussed.

Высокоэффективный квантовый транзистор с системой загрузки состояний и памятью в интегральной схеме

Ю.А. Харламова, Н.М. Арсланов, А.Ю. Чернявский, С.А. Моисеев

Наноиндустрия  Т.15, Номер S8-2(113), 524-529 (2022)

DOI: 10.22184/1993-8578.2022.15.8s.524.529

Предлагается высокоэффективная интегральная схема квантового транзистора, представляющего собой атомнофотонную молекулу в виде линейной цепочки из трех микрорезонаторов, каждый из которых содержит один резонансный трехуровневый атом и подключен к волноводам для загрузки и считывания фотонных кубитов. Схема транзистора масштабируема и может быть использована для выполнения квантового логического элемента CNOT с близкой к единице эффективностью для передачи фотонного кубита между атомами транзистора и обратимой загрузки фотонного кубита в атомы резонаторов.

Реализация протокола оптической квантовой памяти в волноводной структуре в кристалле TM3+:Y3AL5O12

А.В. Павлов, М.М. Миннегалиев, К.И. Герасимов, Р.В. Урманчеев, Т.А. Рупасов, Е.С. Моисеев, А.А. Калинкин, С.П. Кулик , С.А. Моисеев

Наноиндустрия  Т.15, Номер S8-2(113), 530-536 (2022)

DOI: 10.22184/1993-8578.2022.15.8s.530.536

В настоящей работе был реализован протокол оптической квантовой памяти в схеме восстановления сигнала подавленного эха в одномодовой волноводной структуре, сформированной кристалле Tm3+:Y3Al5O12, актуальной для создания интегральной квантовой памяти в кристаллах, активированных редкоземельными ионами.


Linear Stark effect in Y3Al5O12 : Tm3+ crystal and its application in the addressable quantum memory protocol

M. M. Minnegaliev, K. I. Gerasimov, R. V. Urmancheev, A. M. Zheltikov, and S. A. Moiseev

Phys. Rev. B 103, 174110 (2021)

DOI: 10.1103/PhysRevB.103.174110

We report an observation of the linear Stark effect in a Tm3+:Y3Al5O12 crystal with the distribution of the Stark coefficient over the ion ensemble. We associate this effect with local lattice distortions near the positions of Tm3+ ions. Using this effect, the addressable storage of a series of weak light pulses in a cavity-assisted scheme of the revival of silenced echo quantum memory protocol is implemented. In this memory scheme, we also demonstrate storage of a light pulse on the few photon level. The application of an optical resonator makes it possible to increase the memory efficiency in this crystal and to reduce the minimal number of photons in the input signal pulse to 5.6 for the signal-to-noise ratio of 1 in the retrieved echo pulse. The results are in good agreement with the theoretical analysis. The possible ways of the further improvement of the implemented memory scheme are also discussed.

Effect of Laser Radiation near 1.5 µm on the Photoluminescence Parameters and the Ensemble of NV Centers in Diamond

M.A. Smirnov, M.M. Minnegaliev, I.V. Fedotov, S.A. Moiseev, A.M. Zheltikov

JETP Letters 113, pp. 1-6 (2021)

DOI: 10.1134/S0021364021010094

The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths.


Photon echoes in optically dense media

S.A. Moiseev, M. Sabooni, and R.V. Urmancheev

Phys. Rev. Research 2, 012026(R) (2020)

DOI: 10.1103/PhysRevResearch.2.012026

Coherent nonlinear multipulse processes, nonlinear waves, and echo effects in resonant media are the topical problems of modern optics and important tools of coherent spectroscopy and quantum information science. We generalize the McCall-Hahn area theorem to the formation of an arbitrary photon echo generated during the multipulse excitation of the optically dense resonant media. The derived theorem made it possible to reveal the nonlinear mechanism of generation and evolution of the photon echo signals inside the media after a two-pulse excitation. We find that a series of self-reviving echo signals with a total area of 2π or 0π is excited and propagates in the media depth, with each pulse having an individual area less than π. The resulting echo pulse train is an alternative to the well-known soliton or breather. The developed pulse-area approach paves the way for more precise coherent spectroscopy, studies of different photon echo signals, and quantum control of light pulses in the optically dense media.


Two-pulse photon echo area theorem in an optically dense medium

R.V. Urmancheev, K.I. Gerasimov,  M.M. Minnegaliev, T. Chanelière, A. Louchet-Chauvet,  S.A.  Moiseev

Optics Express 27, pp. 28983-28997 (2019)

DOI: 10.1364/OE.27.028983

We perform a theoretical and experimental study of the two-pulse photon echo area conservation law in an optically dense medium. The experimental properties of the echo signal are studied at 4K on the optical transition  3 H 6(1)3 H 4(1) (793 nm) of Tm3+ in a YAG crystal for a wide range of pulse areas of the two incoming light pulses, up to θ1rox4π and θ27π respectively, with optical depth 1.5. We analyze the experimental data by using the analytic solution of the photon echo area theorem for plane waves. We find that the transverse Gaussian spatial profile of the beam leads to an attenuation of the echo area nutation as function of θ1 and θ2. Additional spatial filtering of the photon echo beam allows to recover this nutation. The experimental data are in good agreement with the solution of photon echo pulse area theorem for weak incoming pulse areas θ1,2π. However at higher pulse areas, the observations diverge from the analytic solution requiring further theoretical and experimental studies.

Quantum random numbers from a fiber-optic photon-pair source

M.A. Smirnov, K.V. Petrovnin, I.V. Fedotov, S. A. Moiseev and A. M. Zheltikov

Laser Physics Letters 16 (11), 115402 (2019)

DOI: 10.1088/1612-202X/ab3f9c

We demonstrate a fiber-optic source of random numbers in which random-number generation (RNG) is implemented via an inherently quantum process—detection of correlated photon pairs produced by spontaneous four-wave mixing (FWM) inside an optical fiber. The detection times of individual photon pairs, generated in our RNG scheme via phase-matched FWM in a highly nonlinear photonic-crystal fiber with a suitable dispersion profile, are converted into megabit-size binary sequences, serving as strings of random numbers. The randomness of these bit strings is verified by the National Institute of Standards and Technology Statistical Test Suite. We identify FWM regimes in which mode-locked short-pulse laser sources can provide a high peak power needed to drive photon-pair generation in optical fibers without an excessive loss of randomness due to unwanted patterns in the RNG photon-pair output.

Crystal field and hyperfine structure of Er3+167 in YPO4:Er single crystals: High-resolution optical and EPR spectroscopy

M.N. Popova, S.A. Klimin, S.A. Moiseev, K.I.Gerasimov, M.M. Minnegaliev, E.I. Baibekov, G.S. Shakurov, M. Bettinelli, M.C.Chou

Physical Review B 99, 235151 (2019)

DOI: 10.1103/PhysRevB.99.235151

We report on a high-resolution optical and magneto-optical spectroscopy, luminescence, and electron paramagnetic resonance (EPR) studies of yttrium orthophosphate single crystals doped with erbium, which are promising telecom-wavelength materials for applications in quantum electronics and quantum information processing. An observation of the hyperfine structure in optical spectra of 167Er isotope in Er:YPO4 is presented. Energies and symmetries of 40 crystal-field levels of Er3+ in Er:YPO4 and g factors of some of them were determined and successfully modeled on the basis of crystal-field calculations. The obtained set of crystal-field parameters was used in modeling the hyperfine structure observed in the optical and EPR spectra of Er:YPO4 single crystals.

Investigation of a Sequence of Dynamical Decoupling Pulses for Dipole-Coupled Spin Systems with Inhomogeneous Broadening

M.M. Minnegaliev, R.V. Urmancheev, V.A. Skrebnev , S.A. Moiseev

Optics ans Spectroscopy 126, pp. 1-5 (2019)

DOI: 10.1134/S0030400X19010120

The protocol of dynamic decoupling using a sequence of resonance RF pulses with different shapes in a system of dipole-coupled electron/nuclear spins with inhomogeneous broadening of the resonance line has been theoretically studied. The choice of optimal RF pulse parameters for implementation of long-lived broadband quantum memory based on these spin systems is discussed.

Broadband quantum light on a fiber-optic platform: from biphotons and heralded single photons to bright squeezed vacuum

K.V. Petrovnin, M.A. Smirnov, I.V. Fedotov, A.A  Voronin, I.Z. Latypov, A.G. Shmelev,  A.A. Talipov, T.V. Matveeva, A.B. Fedotov, S. A. Moiseev and A. M. Zheltikov

Laser Physics Letters 16, 075401 (2019)

DOI: 10.1088/1612-202X/ab1483

Four-wave mixing (FWM) of ultrashort laser pulses in a highly nonlinear photonic-crystal fiber is shown to provide a multimodal source of broadband quantum states of light. In the regime of low pump powers, generation of two-photon states and heralded single photons with a bandwidth up to  ≈6 THz is demonstrated within an FWM-sideband tunability range of  ≈55 THz. In the modality of heralded single-photon generation, three-detector measurements of the conditional second-order correlation function reveal a strong antibunching in the signal-photon channel, with more than 99.2% of the signal counts identified as truly single-photon states. At high pump powers, two-detector signal-idler correlation function measurements indicate broadband bright squeezed vacuum generation.


Sequences of the ranged amplitudes as a universal method for fast noninvasive characterization of SPAD dark counts

M.A. Smirnov, N.S. Perminov, R.R. Nigmatullin, A.A. Talipov, S.A. Moiseev

Applied optics 57, pp. 57-61 (2018)

DOI: 10.1364/AO.57.000057

Single-photon detectors based on avalanche photodiodes (SPADs) are key elements of many modern highly sensitive optical systems. One of the bottlenecks of such detectors is an afterpulsing effect, which limits detection rate and requires an optimal hold-off time. In this paper, we propose a novel approach for statistical analysis of SPAD dark counts, and we demonstrate its usefulness for the search of the experimental condition where the afterpulsing effect can be strongly eliminated. This approach exploits a sequence of ranked time intervals between the dark counts and does not contain a complex mathematical analysis of the experimental data. We show that the approach can be efficiently applied for a small number of the dark counts, and it seems to be very beneficial for practical fast characterization of SPAD devices.

Realization of the revival of silenced echo (ROSE) quantum memory scheme in orthogonal geometry

M.M. MinnegalievK.I. GerasimovR.V. UrmancheevS.A. MoiseevT. Chanelière, A. Louchet-Chauvet

AIP Conference Proceedings 1936, 020012 (2018)

DOI: 10.1063/1.5025450

We demonstrated quantum memory scheme on revival of silenced echo in orthogonal geometry in Tm3+: Y3Al5O12 crystal. The retrieval efficiency of ∼14% was demonstrated with the 36 µs storage time. In this scheme for the first time we also implemented a suppression of the revived echo signal by applying an external electric field and the echo signal has been recovered on demand if we then applied a second electric pulse with opposite polarity. This technique opens the possibilities for realizing addressing in multi-qubit quantum memory in Tm3+: Y3Al5O12 crystal.

Quantum memory in the revival of silenced echo scheme in an optical resonator

M.M. MinnegalievK.I. GerasimovR.V. Urmancheev, S.A. Moiseev

Quantum Electronics, 48(10), pp. 894-897 (2018)

DOI: 10.1070/QEL16762

The protocol of optical quantum memory in the revival of silenced photon echo (ROSE) scheme is experimentally implemented in a Tm3+ :Y3Al5O12 crystal (c = 0.1 at.%) placed in an impedance-matched optical Fabry–Perot resonator. The input signal recovery efficiency of ∼21 % is achieved for a light pulse with a storage time of 36 μs. The main sources of loss and their impact on the achieved quantum efficiency are discussed, as well as the advantages of the implemented scheme and the possibilities of the further improvement of the main parameters of quantum memory.

Photon echo area theorem for Gaussian laser beams

R.V. UrmancheevK.I. GerasimovM.M. MinnegalievS.A. MoiseevT. Chanelière, and A. Louchet-Chauvet 

AIP Conference Proceedings, 1936, 020013 (2018)

DOI: 10.1063/1.5025451

We present the results of experimental and theoretical investigation of pulse area theorem for understanding general properties of two pulse (primary) photon echo in the optically deep Tm3+:Y3Al5O12 crystal. Despite discussed limitations the proposed approach allows us to describe the key feature of area theorem dependence introduced by the Gaussian spatial profile of the pulses: the absence of expected downfall to zero at second pulse area θ20 = 2π in the experimental data.

Observation and investigation of narrow optical transitions of 167Er3+ ions in femtosecond laser printed waveguides in 7LiYF4 crystal

M.M. MinnegalievI.V. DyakonovK.I. GerasimovA.A. KalinkinS.P. KulikS.A. MoiseevM.Yu. Saygin and R.V. Urmancheev 

Laser Physics Letters, 15(4), 045207 (2018)

DOI: 10.1088/1612-202X/aaa6a6

We produced optical waveguides in the 167Er$^{3+}:^7$ LiYF4 crystal with diameters ranging from 30 to 100 μm by using the depressed-cladding approach with femtosecond laser. Stationary and coherent spectroscopy was performed on the 809 nm optical transitions between the hyperfine sublevels of 4I15/2 and 4I9/2 multiplets of 167Er3+ ions both inside and outside of waveguides. It was found that the spectra of 167Er3+ were slightly broadened and shifted inside the waveguides compared to the bulk crystal spectra. We managed to observe a two-pulse photon echo on this transition and determined phase relaxation times for each waveguide. The experimental results show that the created crystal waveguides doped by rare-earth ions can be used in optical quantum memory and integrated quantum schemes.

Experimental realization of revival of silenced echo memory protocol in optical cavity

M.M. Minnegaliev, K.I. Gerasimov, R.V. Urmancheev, S.A. Moiseev 

EPJ Web of Conferences 190, 03007 (2018)

DOI: 10.1051/epjconf/201819003007

We demonstrated a photon echo quantum memory for weak input optical pulses on the ROSE protocol in a Tm3+:Y3Al5O12 crystal placed in impedance-matched optical cavity. The quantum efficiency of 21% for a storage of time of 36 µs was achieved for single light pulses.

Generating maximally-path-entangled number states in two spin ensembles coupled to a superconducting flux qubit

Yusef Maleki and Aleksei M. Zheltikov

Phys. Rev. A 97, 012312 (2018)

DOI: 10.1103/PhysRevA.97.012312

An ensemble of nitrogen-vacancy (NV) centers coupled to a circuit QED device is shown to enable an efficient, high-fidelity generation of high-N00N states. Instead of first creating entanglement and then increasing the number of entangled particles N, our source of high-N00N states first prepares a high-Fock state in one of the NV ensembles and then entangles it to the rest of the system. With such a strategy, high-N N00N states can be generated in just a few operational steps with an extraordinary fidelity. Once prepared, such a state can be stored over a longer period of time due to the remarkably long coherence time of NV centers.

Two-photon imaging of fiber-coupled neurons

M.S. Pochechuev, I.V. Fedotov, O.I. Ivashkina, M.A. Roshchina, K.V. Anokhin, A.M. Zheltikov

J. Biophotonics, 11: e201600203 (2018)

DOI: 10.1002/jbio.201600203

Optical coupling between a single, individually addressable neuron and a properly designed optical fiber is demonstrated. Two‐photon imaging is shown to enable a quantitative in situ analysis of such fiber–single‐neuron coupling in the live brain of transgenic mice. Fiber‐optic interrogation of single pyramidal neurons in mouse brain cortex is performed with the positioning of the fiber probe relative to the neuron accurately mapped by means of two‐photon imaging. These results pave the way for fiber‐optic interfaces to single neurons for a stimulation and interrogation of individually addressable brain cells in chronic in vivo studies on freely behaving transgenic animal models, as well as the integration of fiber‐optic single‐neuron stimulation into the optical imaging framework.

     Reconnectable fiberscopes for chronic in vivo deep‐brain imaging

M. S. Pochechuev, I. V. Fedotov, O. I. Ivashkina, M. A. Roshchina, D.V. Meshchankin, D. A. Sidorov‐Biryukov, A. B. Fedotov, K. V. Anokhin, A. M. Zheltikov

J. Biophotonics. 2018; e201700106.

DOI: 10.1002/jbio.201700106

Reconnectable bundles consisting of thousands of optical fibers are shown to enable high‐quality image transmission, offering a platform for the creation of implantable fiberscopes for minimally invasive in vivo brain imaging. Experiments on various lines of transgenic mice verify the performance of this fiberscope as a powerful tool for chronic in vivo neuroimaging using genetically encoded calcium indicators, neuronal activity markers as well as axon growth regulators and brain‐specific protein drivers in deep regions of live brain.

      Free-beam soliton self-compression in air

P. A. Zhokhov & A. M. Zheltikov

Scientific Reports V. 8, Article number: 1824 (2018)

DOI: 10.1038/s41598-017-18624-z

We show that a broadly accepted criterion of laser-induced breakdown in solids, defining the laserbreakdown threshold in terms of the laser fluence or laser intensity needed to generate a certain fraction of the critical electron density rc within the laser pulse, fails in the case of high-intensity fewcycle laser pulses. Such laser pulses can give rise to subcycle oscillations of electron density ρ with peak ρ values well above ρc even when the total energy of the laser pulse is too low to induce a laser damage of material. The central idea of our approach is that, instead of the ρ = ρc ratio, the laser-breakdown threshold connects to the total laser energy coupled to the electron subsystem and subsequently transferred to the crystal lattice. With this approach, as we show in this work, predictions of the physical model start to converge to the available experimental data.

     Broadband multiresonator quantum memory-interface

S. A. MoiseevK. I. Gerasimov, R. R. Latypov, N. S. Perminov, K. V. Petrovnin & O. N. Sherstyukov

Scientific Reports V. 8, Article number: 3982 (2018)

DOI: 10.1038/s41598-018-21941-6

In this paper we experimentally demonstrated a broadband scheme of the multiresonator quantum memory-interface. The microwave photonic scheme consists of the system of mini-resonators strongly interacting with a common broadband resonator coupled with the external waveguide. We have implemented the impedance matched quantum storage in this scheme via controllable tuning of the mini-resonator frequencies and coupling of the common resonator with the external waveguide. Proof-of-principal experiment has been demonstrated for broadband microwave pulses when the quantum efficiency of 16.3% was achieved at room temperature. By using the obtained experimental spectroscopic data, the dynamics of the signal retrieval has been simulated and promising results were found for high-Q mini-resonators in microwave and optical frequency ranges. The results pave the way for the experimental implementation of broadband quantum memory-interface with quite high efficiency η > 0.99 on the basis of modern technologies, including optical quantum memory at room temperature.

     Sequences of the ranged amplitudes as a universal method for fast noninvasive characterization of SPAD dark counts

Maksim A. Smirnov, Nikolay S. Perminov, Raoul R. Nigmatullin, Anvar A. Talipov, and Sergey A. Moiseev

Applied Optics Vol. 57, Issue 1, pp. 57-61 (2018)

DOI: 10.1364/AO.57.000057

Single-photon detectors based on avalanche photodiodes (SPADs) are key elements of many modern highly sensitive optical systems. One of the bottlenecks of such detectors is an afterpulsing effect, which limits detection rate and requires an optimal hold-off time. In this paper, we propose a novel approach for statistical analysis of SPAD dark counts, and we demonstrate its usefulness for the search of the experimental condition where the afterpulsing effect can be strongly eliminated. This approach exploits a sequence of ranked time intervals between the dark counts and does not contain a complex mathematical analysis of the experimental data. We show that the approach can be efficiently applied for a small number of the dark counts, and it seems to be very beneficial for practical fast characterization of SPAD devices.


       Self-compression of high-peak-power mid-infrared pulses in anomalously dispersive air

DOI: 10.1364/OPTICA.4.001405

We identify and experimentally demonstrate a physical scenario whereby high-peak-power mid-infrared (mid-IR) pulses can be compressed as a part of their free-beam spatiotemporal evolution within the regions of anomalous dispersion in air to yield few-cycle subterawatt field waveforms. Unlike filamentation-assisted pulse compression, the pulse-compression scenario identified in this work does not involve any noticeable ionization of air, enabling a whole-beam self-compression of mid-IR laser pulses without ionization-induced loss. Ultrashort high-peak-power 3.9 μm laser pulses are shown to exhibit such self-compression dynamics when exposed to the dispersion anomaly of air induced by the asymmetric-stretch rovibrational band of carbon dioxide. Even though the group-velocity dispersion cannot be even defined as a single constant for the entire bandwidth of mid-IR laser pulses used in experiments, with all soliton transients shattered by high-order dispersion, 100–200 GW, 100 fs, 3.9 μm laser pulses can be compressed in this regime to 35 fs subterawatt field waveforms.

       Dynamical theory of photon superradiative emission by nanoparticle system of Bose-condensed magnons

Sergey N. Andrianov, Sergey A. Moiseev

Eur. Phys. J. B (2017) 90: 165.

DOI: 10.1140/epjb/e2017-80328-8

We have shown the possibility of non-Dicke superradiance for non-ideal magnon Bose-Einstein condensate (BEC) in a broadband frequency bath. Here, it is found that all the stored energy in the system of Bose-condensed magnons can be irradiated into a short pulse with a time delay caused by the strong frequency modulation of magnons due to direct inter-particle interactions in the Bose-condensed state. The last mechanism radically distinguishes this effect from the well-known Dicke superradiance of two-level atomic ensemble where the delay is connected with enhancement of the inter-atomic correlations due to exchange by virtual photons. In our case, the superradiance is the consequence of Bose-condensation in the coherent state where the particles are coupled by direct interaction. We have discussed the conditions for observation of this effect for Bose-condensed magnons in a solid-state sample with a spatial size smaller comparing with the wavelength of the emitted field. In general, we had shown that this kind of superradiance can proceed in samples with ferromagnetic type interaction. As for the antiferromagnetic ones, the effect of magnon superradiance takes place without delay.

     Controllable two-color dispersive wave generation in argon-filled hypocycloid-core kagome fiber

Fanchao Meng, Bowen Liu, Sijia Wang, Junku Liu, Yanfeng Li, Chingyue Wang, A. M. Zheltikov, and Minglie Hu

Optics Express Vol. 25, Issue 26, pp. 32972-32984 (2017)

DOI: 10.1364/OE.25.032972

We demonstrate two-color dispersive wave emission in the ultraviolet and near-infrared regions in an argon filled hypocycloid-core kagome fiber pumped by a femtosecond laser around 1 μm. These two dispersive waves show drastically distinct features in terms of bandwidth and tunability. The dispersive wave in the ultraviolet region has a bandwidth of tens of nanometers and can be widely tuned from at least 267 nm to 460 nm by changing the gas pressure, input pulse energy, and pump wavelength. In contrast, the dispersive wave in the near-infrared region has a narrower bandwidth of ~5 nm and is quite stably positioned near the edge of the fundamental transmission band even if the gas pressure or input pulse energy is significantly changed. An antiresonant tube model is applied to explain the experimental results and a good agreement is found between them. The dynamics show that the narrow-band dispersive wave in the near-infrared region originates from the steep slope of the dispersion near the edge of the transmission band.

       Optimal periodic frequency combs for high-efficiency optical quantum memory based on rare-earth ion crystals

N.M. Arslanov and S.A. Moiseev

Quantum Electron. 47 783 (2017)

DOI: 10.1070/QEL16467

The possibility of enhancing the quantum efficiency of photon echo broadband quantum memory in rare-earth-ion-doped crystals with a frequency comb structure of optical transition inhomogeneous broadening is studied. We have found the optimal parameters of the frequency combs for implementing the pre-assigned quantum efficiency in the chosen spectral range of the optical transitions of rare-earth ions with real parameters. The obtained results allow the conditions to be formulated for increasing the efficiency of broadband quantum memory. The possibilities of experimental implementation of such memory are also discussed.

       Photon echo of an ultranarrow optical transition of 167Er3+ in 7LiYF4 crystals

M.M. MinnegalievE.I. BaibekovK.I. GerasimovS.A. MoiseevM.A. Smirnov and R.V. Urmancheev

Quantum Electron. 47 778 (2017)


The longitudinal and transverse relaxation times for a transition between hyperfine sublevels of the lower electronic states of the 4I15/2 and 4I9/2 multiplets of 167Er3+ ions in 7LiYF4 crystals have been determined for the first time using two-pulse and stimulated photon echo measurements in zero magnetic field at a temperature of 4 K. The decay of the photon echo signal has been shown to be modulated, which is tentatively attributed to the superhyperfine interaction of the 167Er3+ ions with their 19F nearest neighbours. The contributions of various types of interaction to the ultranarrow linewidth (~24 MHz) of the transition in question are discussed. Our results demonstrate that this optical transition of the 167Er3+ ion in 7LiYF4 crystals is potentially attractive for use in Raman quantum memory schemes.

     Mapping anomalous dispersion of air with ultrashort mid-infrared pulses

A. V. Mitrofanov, A. A. Voronin, D. A. Sidorov-Biryukov, M. V. Rozhko, E. A. Stepanov, A. B. Fedotov, V. Shumakova, S. Ališauskas, A. Pugžlys, A. Baltuška & A. M. Zheltikov

Scientific Reports V. 7, Article number: 2103 (2017)

DOI: 10.1038/s41598-017-01598-3

We present experimental studies of long-distance transmission of ultrashort mid-infrared laser pulses through atmospheric air, probing air dispersion in the 3.6–4.2-μm wavelength range. Atmospheric air is still highly transparent to electromagnetic radiation in this spectral region, making it interesting for long-distance signal transmission. However, unlike most of the high-transmission regions in gas media, the group-velocity dispersion, as we show in this work, is anomalous at these wavelengths due to the nearby asymmetric-stretch rovibrational band of atmospheric carbon dioxide. The spectrograms of ultrashort mid-infrared laser pulses transmitted over a distance of 60 m in our experiments provide a map of air dispersion in this wavelength range, revealing clear signatures of anomalous dispersion, with anomalous group delays as long as 1.8 ps detected across the bandwidth covered by 80-fs laser pulses.

        Microwave Spin Frequency Comb Memory Protocol Controlled by Gradient Magnetic Pulses

Gerasimov, K.I., Moiseev, S.A. & Zaripov, R.B.

Appl. Magn. Reson.  V. 48Issue 8, pp 795–804 (2017)


We have demonstrated a combination of frequency comb spin-echo protocol in a conventional microwave pulsed electron spin resonance spectrometer with gradient pulses of the external magnetic field applied for on-demand retrieval of signal microwave pulses at the required moments of time. A natural high-finesse periodic structure was used as a carrier of stored information. The structure is made out of hyperfine lines of electron spin resonance of tetracyanoethylene anion radicals in toluene at room temperature. Herein, we have also observed that using the pulses of gradient magnetic field can increase the memory capacity. The experimental results demonstrated promising opportunities for controlling electron nuclear spin coherence, which could be useful for implementation of broadband microwave or optical-microwave noise free quantum memory protocols.

       Single photon transfer controlled by excitation phase in a two-atom cavity system

Chun Xiao Zhou, Rui Zhang, Miao Di Guo, S. A. Moiseev,  and Xue Mei Su

We investigate the quantum interference effect of single photon transfer in a two-atom cavity system caused by the excitation phase. In the proposed system, the two identical atoms are firstly put into a timed state by an external single photon field. During the excitation, the atoms grasp different phases which depend on the spatial position of the atoms. Due to the strong resonant interaction between the atoms and optical cavity mode, the absorbed input photon can be efficiently transferred from the atoms to the cavity mode. We show that photon transfer is sensitive to the quantum interference caused by the excitation phases of atoms. The atomic positions can also determine the coupling constants between the atoms and cavity mode as well as the interatomic dipole–dipole interaction which causes additional interference effects on the quantum transfer. Based on the characteristics of the excitation phase, we find that it is a feasible scheme to generate a long-lived dark state and it could be useful for storage and manipulation of single photon fields by controlling the excitation phase.

J. Phys. B: At. Mol. Opt. Phys. 50125501 (2017).


         Квантовая память в ортогональной геометрии восстановления спящего эха

К. И. Герасимов, М. М. Миннегалиев, С. А. Моисеев,  Р.В. Урманчеев, T. Chanelière and A. Louchet-Chauvet

Оптика и спектроскопия т. 123, № 2 (2017)

Экспериментально реализован протокол квантовой памяти, основанный на восстановлении спящего эха (ROSE) в кристалле Tm3+:Y3Al5O12 в схеме с ортогональной геометрией распространения сигнального и контролирующего световых полей, которая наиболее удобна для дальнейшей реализации высокоэффективной квантовой памяти в одномодовом оптическом резонаторе. В данной схеме продемонстрирована эффективность восстановления сигнала спящего эха ~13% при времени хранения 36 mс. Также показана возможность записи и считывания последовательностей из нескольких световых импульсов. Рассмотрены достоинства и недостатки представленной схемы, предложены способы увеличения эффективности и времени хранения.

       Multiresonator Quantum Memory

Moiseev S.A., Gubaidullin F.F., Kirillov R.S., Latypov R.R., Perminov N.S., Petrovnin K.V., Sherstyukov O.N.

Phys. Rev. A 95, 012338 (2017)

DOI: 10.1103/PhysRevA.95.012338

In this paper we present universal broadband multiresonator quantum memory based on the spatial-frequency combs of the microresonators coupled with a common waveguide. We find a Bragg-type impedance matching condition for the coupling of the microresonators with a waveguide field that provides an efficient broadband quantum storage. The analytical solution obtained for the microresonator fields enables sustainable parametric control of all the memory characteristics. We also construct an experimental prototype of the studied quantum memory in the microwave spectral range that demonstrates basic properties of the microwave microresonators, their coupling with a common waveguide, and independent control of the microresonator frequencies. Experimentally observed narrow lines of the microresonators confirm the possibility of multiresonator quantum memory implementation.

DOI: 10.1103/PhysRevA.95.012338

     A transversely localized light in waveguide: the analytical solution and its potential application

Narkis M. Arslanov, Ali A. Kamli, Sergey A. Moiseev

Laser Physics 27, 025103 (5pp)  (2017).


Investigation of light in waveguide structures is a topical modern problem that has long-standing historical roots. A parallel-plate waveguide is a basic model in these studies and is intensively used in numerous investigations of nano-optics, integrated circuits and nanoplasmonics. In this letter we have first found an approximate analytical solution which describes the light modes with high accuracy in the subwavelength waveguides. The solution provides a way of obtaining a clear understanding of the light properties within the broadband spectral range in the waveguide with various physical parameters. The potential of the analytical solution for studies of light fields in the waveguides of nano-optics and nanoplasmonics has also been discussed.

      All-optical photon echo on a chip

Moiseev, E.S., Moiseev, S.A.

Laser Physics Letters, Volume 14, Number 1, 015202 (2017)


We demonstrate that a photon echo can be implemented by all-optical means using an array of on-chip high-finesse ring cavities whose parameters are chirped in such a way as to support equidistant spectra of cavity modes. When launched into such a system, a classical or quantum optical signal—even a single-photon field—becomes distributed between individual cavities, giving rise to prominent coherence echo revivals at well-defined delay times, controlled by the chirp of cavity parameters. This effect enables long storage times for high-throughput broadband optical delay and quantum memory.

       Photon echo area theorem for optically dense media

R. V. Urmancheev, K. I. Gerasimov, M. M. Minnegaliev and S. A. Moiseev

Bulletin of RAS: Physics — 2017, Vol. 81, N. 5.

In this paper, we generalize McCall Hahn area theorem to the echo pulse irradiation in the optically depth medium where absorption line consists of several unresolved spectral optical transitions and is characterized by a symmetrical form. Some of the obtained analytical results are compared with experimental studies in Tm3+:Y3Al5O12  crystal at 793 nm.

Optimal conditions of quantum memory for spatial frequency grating of resonators

N. S. Perminov, R. S. Kirillov, R. R. Latypov, S. A. Moiseev and O. N. Sherstyukov

Bulletin of RAS: Physics — 2017, Vol. 81, N. 5.

We study the dynamics of the interaction of microcavities that are connected to the common waveguide in the circuit multiresonator quantum memory. Were obtained optimal conditions for the implementation of quantum memory and dynamic picture of the energy exchange between different microcavities.


       High-resolution Magneto-optical Spectroscopy of 7LiYF4: 167Er3+, 166Er3+ and Analysis of Hyperfine Structure of Ultra Narrow Optical Transitions

K.I. Gerasimov, M.M. Minnegaliev, B.Z. Malkin, E.I. Baibekov, and S.A. Moiseev

Phys. Rev. B 94, 054429 (2016).


We performed high-resolution magneto-optical spectroscopy of the hyperfine transitions from 4I15/2 to the 4I13/2 and 4I9/2 multiplets of 167Er3+ and 166Er3+ in an isotopically purified 7LiYF4 crystal in various external magnetic fields up to 0.7 T. The obtained experimental results are interpreted in the framework of the generalized theoretical approach. The derived model successfully explains all the experimentally observed optical hyperfine transitions by using a single set of basic parameters found for the crystal-field interaction, magnetic dipole and electric quadrupole hyperfine interactions, together with Zeeman interactions at different orientations of the external magnetic field. A number of the studied quantum transitions appears to be promising for use in Raman quantum storage at optical telecommunication wavelengths.

     Secure polarization-independent subcarrier quantum key distribution in optical fiber channel using BB84 protocol with a strong reference

Gleim A.V., Egorov V.I., Nazarov Y.V., Smirnov S.V., Chistyakov V.V., Bannik O.I., Anisimov A.A., Kynev S.M., Ivanova A.E., Collins R.J., Kozlov S.A., Buller G.

Optics express — 2016, Vol. 24, No. 3, pp. 2619-2633.


A quantum key distribution system based on the subcarrier wave modulation method has been demonstrated which employs the BB84 protocol with a strong reference to generate secure bits at a rate of 16.5 kbit/s with an error of 0.5% over an optical channel of 10 dB loss, and 18 bits/s with an error of 0.75% over 25 dB of channel loss. To the best of our knowledge, these results represent the highest channel loss reported for secure quantum key distribution using the subcarrier wave approach. A passive unidirectional scheme has been used to compensate for the polarization dependence of the phase modulators in the receiver module, which resulted in a high visibility of 98.8%. The system is thus fully insensitive to polarization fluctuations and robust to environmental changes, making the approach promising for use in optical telecommunication networks. Further improvements in secure key rate and transmission distance can be achieved by implementing the decoy states protocol or by optimizing the mean photon number used in line with experimental parameters.

     Revealing beam-splitting attack in a quantum cryptography system with a photon-numberresolving detector

Gaidash A., Egorov V., Gleim A.

Journal of the Optical Society of America B: Optical Physics — 2016, Vol. 33, No. 7, pp. 1451-1455.


We discuss a method for revealing a photon-number-splitting (PNS) attack in a quantum key distribution (QKD) system, which is based on analyzing the statistical distribution of photon numbers detected in each time interval. A relation for estimating the difference between the expected photon-number distribution and the one appearing in the course of a PNS attack is derived. An equation defining the minimum number of counts necessary for revealing the attack with desired probability is given. Formulas for calculating the amount of raw keys known to an illegitimate user due to a PNS attack are obtained depending on the system’s total loss. The main advantage of the method is the possibility of using it in QKD systems without significant modifications in the protocol or experimental setup.

      Using of optical splitters in quantum random number generators, based on fluctuations of vacuum

Ivanova A.E., Chivilikhin S.A., Gleim A.V.

Journal of Physics: Conference Series — 2016, Vol. 735, No. 1, pp. 012077.

DOI: 10.1088/1742-6596/735/1/012077

In this paper mathematical description of using of fiber Y-splitter and optical splitter with two input and two output ports in quantum random number generation systems were obtained.

     Implementation of decoy states in a subcarrier wave quantum key distribution system

Gaidash A.A., Kozubov A.V., Egorov V.I., Gleim A.V.

Journal of Physics: Conference Series — 2016, Vol. 741, No. 1, pp. 012090.


Subcarrier wave quantum key distribution systems demonstrate promising capabilities for secure quantum networking. However for this class of devices no implementation of secure decoy states protocol was developed. It leaves them potentially vulnerable to photon-number splitting attacks on quantum channel and limiting the key distribution distance. We propose a practical solution to this problem by calculating the required parameters of light source and modulation indices for signal and decoy states in a subcarrier wave system and describing the corresponding experimental scheme.

     Time-bin quantum RAM

Moiseev, E.S., Moiseev, S.A.  

Journal of Modern Optics, Volume 63, Issue 20, pp 2081-2092(2016)

DOI: 10.1080/09500340.2016.1182222

We have proposed a compact scheme of quantum random access memory (qRAM) based on the impedance matched multi-qubit photon echo quantum memory incorporated with the control four-level atom in two coupled QED cavities. A set of matching conditions for basic physical parameters of the qRAM scheme that provides an efficient quantum control of the fast single photon storage and readout has been found. In particular, it has been discovered that the efficient qRAM operations are determined by the specific properties of the excited photonic molecule coupling the two QED cavities. Herein, the maximal efficiency of the qRAM is realized when the cooperativity parameter of the photonic molecule equals to unity that can be experimentally achievable. We have also elaborated upon the new quantum address scheme where the multi-time-bin photon state is used for the control of the four-level atom during the readout of the photonic qubits from the quantum memory. The scheme reduces the required number of logical elements to one. Experimental implementation by means of current quantum technologies in the optical and microwave domains is also discussed.

     High-resolution magneto-optical spectroscopy of 7LiYF4: 167Er3+, 166Er3+  and analysis of hyperfine structure of ultranarrow optical transitions

Gerasimov, K.I.Minnegaliev, M.M., Malkin, B.Z., Baibekov, E.I., Moiseev, S.A.

Phys. Rev. B, Volume 94, Issue 5, 054429 (2016)

DOI: 10.1103/PhysRevB.94.054429

We performed high-resolution magneto-optical spectroscopy of the hyperfine transitions from I15/24 to the I13/24 and I9/24 multiplets of Er3+167 and Er3+166 in an isotopically purified LiYF47 crystal in various external magnetic fields up to 0.7 T. The obtained experimental results are interpreted in the framework of the generalized theoretical approach. The derived model successfully explains all the experimentally observed optical hyperfine transitions by using a single set of basic parameters found for the crystal-field interaction, magnetic dipole and electric quadrupole hyperfine interactions, together with Zeeman interactions at different orientations of the external magnetic field. A number of the studied quantum transitions appears to be promising for use in Raman quantum storage at optical telecommunication wavelengths.

      A quantum computer on the basis of an atomic quantum transistor with built-in quantum memory

Moiseev S. A. , Andrianov S. N.

Optics and Spectroscopy, Volume 121, Issue 6, pp 886–896(2016)

DOI: 10.1134/S0030400X16120195

A quantum transistor based quantum computer where the multiqubit quantum memory is a component of the quantum transistor and, correspondingly, takes part in the performance of quantum logical operations is considered. Proceeding from the generalized Jaynes–Cummings model, equations for coefficients of the wave function of the quantum system under consideration have been obtained for different stages of its evolution in processes of performing logical operations. The solution of the system of equations allows one to establish requirements that are imposed on the parameters of the initial Hamiltonian and must be satisfied for the effective operation of the computer; it also demonstrates the possibility of a universal set of quantum operations. Thus, based on the proposed approach, the possibility of constructing a compact multiatomic ensemble based on quantum computer using a quantum transistor for the implementation of two-qubit gates has been demonstrated.


      Short-cycle pulse sequence for dynamical decoupling of local fields and dipole-dipole interactions

S. A. Moiseev, and V. A. Skrebnev

Phys. Rev. A 91, 022329 (2015)

DOI: 10.1103/PhysRevA.91.022329

We propose an alternate pulse sequence for dynamical averaging of the dipole-dipole interactions and inhomogeneity of the magnetic fields in the nuclear-spin system. The sequence contains a short cycle of the periodic resonant pulse excitation that offers new possibilities for implementing the long-lived multiqubit quantum memory on the condensed spin ensembles that are so important for the construction of a universal quantum computer and long-distance quantum communications.

      Slow light with electromagnetically induced transparency in optical fibre

Agus Muhamad Hatta, Ali A. Kamli, Ola A. Al-Hagan and Sergey A. Moiseev

J. Phys. B: At. Mol. Opt. Phys. 48 155502

DOI: 10.1088/0953-4075/48/15/155502

Slow light with electromagnetically induced transparency (EIT) in the core of optical bre containing three-level atoms is investigated. The guided modes are treated in the weakly guiding approximation which renders the analysis into manageable form. The transparency window and permittivity pro le of the core due to the strong pump eld in the EIT scheme is calculated. For a speci c permittivity pro le of the core due to EIT, the propagation constant of the weak signal eld and spatial shape of fundamental guided mode are calculated by solving the vector wave equation using the nite di erence method. It is found that the transparency window and slow light eld can be controlled via the optical bre parameters. The reduced group velocity of slow light in this con guration is useful for many technological applications such as optical memories, e ective control of single photon elds, optical bu er and delay line.

Symmetric-cycle pulse sequence for dynamical decoupling of local fields and dipole–dipole interactions

S A Moiseev and V A Skrebnev

J. Phys. B: At. Mol. Opt. Phys. 48 (2015) 135503 (5pp)

DOI: 10.1088/0953-4075/48/13/135503

We have proposed a new pulse sequence for the dynamical decoupling of decoherence effects in the ensemble of nuclear spins. The sequence provides a symmetric cycle that offers a strong suppression of the decoherence effects caused by the dipole–dipole interactions and the inhomogeneous local magnetic fields in nuclear spin ensemble dynamics. We have discussed a potential of the proposed pulse sequence for the long-lived storage of the multi-qubit quantum states.


       Stationary and quasistationary light pulses in three-level cold atomic systems

S. A. Moiseev, A. I. Sidorova and B. S. Ham

Phys. Rev.  A 89, 043802 (2014)

DOI: 10.1103/PhysRevA.89.043802

We have studied stationary and quasistationary signal light pulses in cold -type atomic media driven by counterpropagating control laser fields at the condition of electromagnetically induced transparency. By deriving a dispersion relation we present spectral and temporal properties of the signal light pulse and a significant influence of atomic decoherence on the coupled stationary light pulses for spatial splitting. Finally we discuss quasistationary light pulse evolution characterized by frozen spatial spreading for a robust coherent control of slow light pulses.

        Spin frequency comb echo memory controlled by a pulsed-gradient of magnetic field

K. I. Gerasimov, S. A. Moiseev, V. I. Morosov, and R. B. Zaripov

Proc. of SPIE Vol. 9533 953310-1

DOI: 10.1117/12.2185472

The controllable storage and on demand retrieval of the microwave pulses by using the photon echo quantum memory approach based on a spin frequency comb of inhomogeneous broadening (SFC- protocol) have been demonstrated. We have used an electron-nuclear spin ensemble of tetracyanoethylene anion radicals in toluene which has a natural periodic structure of narrow electron-spin resonance (ESR) hyperfine lines. On-demand retrieval of the stored field has been realized by using two pulses of the magnetic field gradient of an opposite polarity which hold the electron spins in a dephased excited state during the storage time. The obtained experimental results demonstrate promising properties for coherent controlling the electron-nuclear spin ensemble of radicals in liquid that could be useful for implementation of room-temperature broadband quantum memory.

      Magnon qubit and quantum computing on magnon Bose-Einstein condensates

S. N. Andrianov and S. A. Moiseev

Phys. Rev. A 90, 042303 (2014)

DOI: 10.1103/PhysRevA.90.042303

Recently, great progress has been made in the creation of a solid-state quantum computer using superconducting qubits on Cooper pairs of charged electrons.However, this approach hasmet limitations due to decoherence effects caused by the strong Coulomb interaction of the superconducting qubitwith the environment. Here, we propose the solution of this problem by switching to another Bose-Einstein condensate (BEC), uncharged long-livedmagnons, wherein the magnon BEC qubit can be realized due to themagnon blockade isolating a pair of themagnon condensate energy levels in the mesoscopic and nanoscopic ferromagnetic dielectric sample.We demonstrate the singlequbit gates by operating quantum transition between these states in the external microwave field.We also consider implementation of the two-qubit gates by using the interaction between such magnon BEC qubits due to exchange by virtual photons in a microwave cavity. Finally, we discuss the condition for long-lived magnon BEC qubits, a scalable architecture, and promising advantages of the multiqubit quantum computer based on the magnon qubit.

      Room-temperature storage of electromagnetic pulses on a high-finesse natural spin-frequency comb

K. I. Gerasimov, S. A. Moiseev, V. I. Morosov and R. B. Zaripov

Phys. Rev. A 90, 042306 (2014)

DOI: 10.1103/PhysRevA.90.042306

We have demonstrated the storage of electromagnetic pulses by exploiting a spin-echo quantum memory protocol. Therein, we have used an electron-nuclear spin ensemble of tetracyanoethylene anion radicals in toluene which has a natural periodic structure of narrow electron-spin resonance (ESR) hyperfine lines. Robust storage up to three temporal modes has been achieved with storage time ∼1 μs at room temperature on a conventional pulsed ESR spectrometer. On-demand retrieval of the stored field has been realized by holding the electron spins in a dephased state during the storage time. A longer storage time and the highest overall finesse ∼20 of the ESR spectrum have been attained by using multipulse dynamical decoupling of the electron spins from the noisy environment. The obtained experimental results suggest that the electron-nuclear spin ensemble of radicals in liquid should be a promising system for the room-temperature quantum memory.

       Kinetics of pulse-induced magnon Bose-Einstein condensate

Sergey N. Andrianov, Vladimir V. Bochkarev, and Sergey Moiseev

Eur. Phys. J. B (2014) 87: 128

DOI: 10.1140/epjb/e2014-41028-3

We have analysed the kinetics of Bose-Einstein condensed (BEC) magnons after pulsed excitation in a ferromagnet at room and low temperatures. For this purpose, we have derived the kinetic
equations using the nonequilibrium statistical operator method to describe the general form of the interactions in the magnon system. On the basis of this approach, we have analysed the nonlinear properties of the magnon BEC kinetics caused by interactions with magnon reservoir modes and phonons. We have found that formation of a quasi-stationary BEC magnon state is possible not only at room temperature but also at low temperatures, where the magnon-phonon interaction leads to formation of a residual BEC state with magnon population much larger than at room temperature. It was also observed that a moderately strong four-particle part of the magnon-magnon interaction violating the number of magnons is sufficient to facilitate magnon BEC formation. The predicted long-lived magnon BEC state could be promising for realisation of macroscopic qubits.