# Tania GolubevaSaint Petersburg State University | SPBU · Faculty of Physics

Tania Golubeva

Dr. Sc.

## About

67

Publications

2,280

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210

Citations

Introduction

Additional affiliations

January 1998 - October 2016

January 1998 - January 2020

## Publications

Publications (67)

The article considers two strategies for decreasing the error of universal single-mode Gaussian transformations implemented using one-way quantum computation on a four-node linear cluster state. We have shown that it is possible to choose the weight coefficients of the cluster state in such a way as to minimize the error of the universal single-mod...

In this paper, we investigate the error correction of universal Gaussian transformations obtained in the process of continuous-variable quantum computations. We have tried to bring our theoretical studies closer to the actual picture in the experiment. When investigating the error correction procedure, we have considered that both the resource GKP...

The application of high-dimensional quantum systems (qudits) in quantum computing and communications seems to be a promising avenue due to the possibility of increasing the amount of information encoded in one physical carrier. In this work, we propose a method for implementing single-qudit gates for qudits based on light modes with orbital angular...

We propose a modified quantum teleportation scheme to increase the teleportation accuracy by applying a cubic phase gate to the displaced squeezed state. We describe the proposed scheme in the Heisenberg picture, evaluating it from the point of view of adding an error in teleportation, and show that it allows achieving less error than the original...

For the first time, the theory and practical realization of a broadband quantum noise generator based on original integrated optical beam splitter in the form of a Mach-Zehnder interferometer is demonstrated. The beam splitter with a double output, made on a lithium niobate substrate, provided accurate electro-optical balancing of the homodyne quan...

We propose a modified quantum teleportation scheme to increase the teleportation accuracy by applying a cubic phase gate to the displaced squeezed state. We have described the proposed scheme in Heisenberg's language, evaluating it from the point of view of adding an error in teleportation, and have shown that it allows achieving less error than th...

Using the quantum teleportation in continuous variables as a test scheme, we compare two entangled transformations—mixing of signals on a beam splitter and by the controlled-Z (cz) operation. We evaluate these transformations in terms of the errors added to teleported oscillators. We have shown that the cz operation leads to the lower error of tele...

The application of high-dimensional quantum systems (qudits) in quantum computing and communications seems to be a promising avenue due to the possibility of increasing the amount of information encoded in one physical carrier. In this work, we propose a method for implementing single-qudit gates for qudits based on light modes with orbital angular...

We demonstrate theoretically the effect of interference, similar to the Hong-Ou-Mandel effect, for two single-photon pulses by writing them sequentially inside a quantum memory cell in a tripod configuration.

The effect of diffraction on the conservation of the quantum state of a quadrature-squeezed light pulse in an ensemble of thermal atoms for a collinear configuration of light fields has been considered. The motion of atoms leads to the fact that when both the signal and control fields propagate in the same direction as when writing, there is an unc...

We demonstrate the effect of interference, similar to the Hong-Ou-Mandel effect, for two single-photon pulses by writing them sequentially inside a quantum memory cell in a tripod configuration.

This paper studies the Raman quantum memory protocol as applied to quantum light with orbital angular momentum. The memory protocol is implemented on an ensemble of three-level cold atoms with the Λ configuration of energy levels. The possibility of storing quantum statistics of light with an orbital momentum is analyzed in the case when the drivin...

In this paper, we estimate the errors of Gaussian transformations implemented using one-way quantum computations on cluster states of various configurations. From all possible cluster state configurations, we choose those that give the smallest computation error. Furthermore, we evaluate errors in hybrid computational schemes, in which Gaussian ope...

The paper studies the Raman quantum memory protocol as applied to quantum light with orbital angular momentum. The memory protocol is implemented on an ensemble of three-level cold atoms with the $\Lambda$- configuration of energy levels. The possibility of storing quantum statistics of light with an orbital momentum is analysed in the case when th...

In this paper, we study the transformations that are obtained in one-way quantum computation on continuous-variable cluster states of various configurations. Of all possible cluster configurations, we choose those that are suitable for universal Gaussian operations.

The Heisenberg-Langevin equation for a spatial laser soliton in a wide-aperture laser with saturable absorption is constructed within the framework of consistent quantum electrodynamics. We discuss in detail the canonical variables for the generation field and the material two-level medium, consisting of centres providing amplification and absorpti...

In the case of a large amount of computation, a situation may arise when the intermediate results of calculations need to be stored for a given time. In this work, we show how to create a hybrid atomic-field cluster state and create a controlled gate in such a way that the results of calculations are recorded under long-lived degrees of freedom of...

In this study, we demonstrate the possibility of the implementation of universal Gaussian computation on a two-node cluster state ensemble. We consider the phase-locked sub-Poissonian lasers, which radiate the bright light with squeezed quadrature, as the resource to generate these states.

In this paper, we discuss the possibility of building a linear cluster state based on modes with a certain orbital angular momentum. We show that in the system under consideration a field with a rich mode structure is generated in the cavity. We also analyze the conditions under which an infinite system of Heisenberg-Langevin equations describing t...

This paper discusses the effect of saturated absorption on the quantum features of a sub-Poissonian laser. It is shown that when both media (laser and absorbing) are saturated, the appearance of an additional element in the cavity does not lead to the demolition of the quantum properties (regular statistics of photons and quadrature squeezing) of l...

In this study, we demonstrate the possibility of the implementation of universal Gaussian computation on a two-node cluster state ensemble. We consider the phase-locked sub-Poissonian lasers, which radiate the bright light with squeezed quadrature, as the resource to generate these states.

This paper discusses the effect of saturated absorption on the quantum features of a sub-Poissonian laser. It is shown that when both media (laser and absorbing) are saturated, the appearance of an additional element in the cavity does not lead to the demolition of the quantum properties (regular statistics of photons and quadrature squeezing) of l...

We consider the problems of constructing a cluster state from a set of orthogonal modes. It is shown that the commonly used unitary transformation is not reduced in this case to a set of standard operations of linear optics performed over fields in a squeezed state, but should be supplemented by a more complicated operation of a noise-free transfor...

In this paper we discuss the possibility of building a linear cluster state based on modes with a certain orbital angular momentum (OAM). We show that in the system under consideration a field with a rich mode structure is generated in the cavity. We also analyze the conditions under which an infinite system of Heisenberg-Langevin equations describ...

In this paper, we assess the possibilities of generating cluster states with different topologies possessed by the finite squeezing resource of the initial oscillators used to generate the cluster state. We obtained the condition on minimum squeezing required for generating a cluster with a given topology as a simple estimation in terms of the coef...

The possibility of cluster-state generation on the basis of mixing radiation from two independent lasers in an asymmetric Mach–Zehnder interferometer is shown in this paper. The formulation of the problem is close to that considered before by Menicucci (Phys. Rev. A 83, 62314 (2011)) and Yokouama et al. (Nature Photonics 7, 982 (2013)). The specifi...

In this article, we employ multimode radiation of a synchronously pumped optical parametric oscillator (SPOPO) to build a cluster state through a conversion on the base of quantum memory cell. We demonstrate that by choosing an appropriate driving field we can ensure the effective writing of the only one supermode from the entire set of the SPOPO s...

In this article, we consider the possibility of manipulation of quantum signals, ensured by the use of the tripod-type atomic memory cell. We show that depending on a configuration of driving fields at the writing and reading, such a cell allows the signal to both be stored and transformed. It is possible to provide the operation of the memory cell...

In this paper, we examined a possibility of preservation of a substantially multimode radiation in a single cell of quantum memory. As a light source we considered a synchronously pumped optical parametric oscillator (SPOPO). As it was shown in [1-4], SPOPO radiation has a large number of the correlated modes making it attractive for the purposes o...

Теоретически исследована запись и считывание двух ортогонально сжатых или перепутанных световых импульсов в ансамбль атомов триподной конфигурации и возможность использования рассматриваемой модели в протоколах квантовой информации как аналог интерферометра Маха-Цендера, либо как источник перепутанных импульсов.

We have considered theoretically the feasibility of the broadband quantum memory based on the resonant tripod-type atomic configuration. In this case, the writing of a signal field is carried out simultaneously into two channels, and characterized by an excitation of two spin waves of the atomic ensemble. With simultaneous read out from both channe...

We show that a protocol of the high-speed quantum memory on an atomic ensemble with a tripod-type configuration can be used as the interferometer of Mach-Zehnder. The attention is focused on the fact that beam splitters of the interferometer can be modified by changing ampli- tudes and phases of driving fields. Also our model can works as a source...

We discuss the influence of atomic thermal motion on the efficiency of multimode quantum memory in two configurations: over the free expand of atoms cooled beforehand in a magneto-optical trap, and over complete mixing of atoms in a closed cell at room temperature. We consider the high-speed quantum memory, and assume that writing and retrieval are...

We discuss the beam-splitter model of quantum memory for demonstrating the connection between the memory efficiency and the multimode storage of the quantum statistical characteristics of light, such as the Mandel parameter and quadrature squeezing. We demonstrate in what sense the beam-splitter model can be applied to characterize the multimode qu...

The possibility of preserving an entangled state of two signal pulses during writing and retrieval processes in a multimode quantum memory is investigated. Two stationary laser sources of light squeezed in two orthogonal quadratures are used for generation of the entangled state. “Carved out” pulses of appropriate duration are mixed on a symmetric...

We discuss the influence of atomic thermal motion on the efficiency of
multimode quantum memory in two configurations: over the free expand of atoms
cooled beforehand in a magneto-optical trap, and over complete mixing of atoms
in a closed cell at room temperature. We consider the high-speed quantum
memory, and assume that writing and retrieval are...

In this article the ability to record, store, and read out the quantum
properties of light is studied. The discussion is based on high-speed and
adiabatic models of quantum memory in lambda-configuration and in the limit of
strong resonance. We show that in this case the equality between efficiency and
squeezing ratio, predicted by the simple beams...

Basing on the simplest single-mode field source, we investigate the role of
the various covariance matrices for reconstructing the field state and
describing its quantum statistical properties. In spite of the fact that the
intracavity field is a single-mode field, we take into account the natural
multimode structure arising in the field, when it l...

We present a general model for an atomic memory using ultra-short pulses of light, which
allows both spatial and temporal multimode storage. The process involves the storage of a
faint quantum light pulse into the spin coherence of the ground state of
Λ-type 3-level atoms, in the presence of a strong driving pulse. Our
model gives a full descriptio...

Quantum properties of pulsed radiation obtained by cutting out a part of the signal from steady� state squeezed �light sources are investigated. The considered sources include a degenerate optical parametric
oscillator, a sub-�Poissonian injection-�locked laser, and a synchronously pumped femtosecond optical parametric oscillator. Based on the stat...

We present a general model for an atomic memory using ultra-short pulses of
light, which allows both spatial and temporal multimode storage. The process
involves the storage of a faint quantum light pulse into the spin coherence of
the ground state of Lambda-type 3-level atoms, in the presence of a strong
driving pulse. Our model gives a full descr...

We study the quantum memory protocol for spatially multimode light based on an atomic ensemble in the Λ-configuration. We
analytically solve a system of partial differential equations that describe the evolution of the medium and field for the
case where the interaction time considerably exceeds the lifetime of the excited state. This time ratio ma...

We study the coherent storage and retrieval of a very short multimode light
pulse in an atomic ensemble. We consider a quantum memory process based on the
conversion of a signal pulse into a long-lived spin coherence via light matter
interaction in an on-resonant Lambda-type system. In order to study the writing
and reading processes we analyticall...

We present a procedure for the measurement of quadrature components of an electromagnetic field in the far field as an alternative to the traditional approach based on the homodyne detection (HD) technique. For that we suggest to use coherent sources such as phase-locked lasers or optical parametric oscillators operating above threshold. Then we sh...

We consider the measuring procedure that in principle allows to avoid the homodyne detection for the simultaneous selection of both quadrature components in the far-field. The scheme is based on the use of the coherent sources of the non-classical light. The possibilities of the procedure are illustrated on the basis of the use of pixellised source...

The degree of purity of the quantum state of electromagnetic field at the output of a degenerate optical parametric oscillator is theoretically analyzed. It is shown that, in the subthreshold and significantly suprathreshold modes, the degree of purity of the state of pairs of waves with frequencies ωs
± Ω (ωs
is the signal mode frequency) is unity...

Information applications of the essentially multimode (in time) radiation of a degenerate optical parametric oscillator operating
above the oscillation threshold, such as protocols of quantum parallel dense coding and multimode quantum teleportation, have
been considered. The stream of Shannon mutual information as a function of the spectral width...

We consider a sub-Poissonian single-mode laser with external synchronization and analyze its applicability to the problems of quantum information. Using Heisenberg-Langevin theory, we calculate the quadrature variances of the field emitted by this laser. It is shown that such systems can demonstrate strong quadrature squeezing. Taking into account...

We have theoretically studied the effects of quantum coherence in a driven quasi-degenerate two-level atomic system. We have shown that the quantum interference, which can be destructive or constructive, can be controlled by an externally applied magnetic field allowing one to implement both electromagnetically induced transparency and electromagne...

In this paper, we investigate several properties of the
full signal-idler-pump mode quantum state generated by a triply
resonant non-degenerate Optical Parametric Oscillator operating
above threshold, with an injected wave on the signal and idler
modes in order to lock the phase diffusion process. We determine
and discuss the spectral purity of thi...

The statistical properties of light emitted by a three-level laser are theoretically investigated. In the model considered the three-level medium is coherently excited by another laser having arbitrary photon statistics. It is shown that under certain conditions the photon statistics of the three-level laser is determined by that of the exciting la...

We propose quantum dense coding protocol for optical images. This protocol extends the earlier proposed dense coding scheme for continuous variables [S.L. Braunstein and H.J. Kimble, Phys. Rev. A 61 042302 (2000)] to an essentially multimode in space and time optical quantum communication channel. This new scheme allows, in particular, for parallel...

A mere correspondence between the electron statistics and the photon one vanishes in the feedback loop (FBL). It means that the direct photodetection, supplying us with the electron statistics, does not provide us with a wished information about the laser photon statistics. For getting this information we should think up another measurement procedu...

We further elaborate the theory of quantum fluctuations in vertical-cavity surface-emitting lasers (VCSEL's), developed by [Hermier et al. Phys. Rev. A 65, 053825 (2002)]. In particular, we introduce quantum Stokes parameters to describe the quantum self-correlations and cross correlations between two polarization compo-nents of the electromagnetic...

The full quantum statistical theory of the vertical-cavity surface-emitting laser (VCSEL) is constructed for arbitrary relations between frequency parameters. In our approach we follow Hermier et al (2002 Phys. Rev. A 65 053825) and Golubev et al (2004 Phys. Rev. A at press; Preprint quant-ph/0407006) and formulate the theory in the form of quantum...

We have shown that quantum interference in a driven quasi-degenerate two-level atomic system can be controlled by an externally applied magnetic field. We demonstrate that the mechanism of optical control is based on quantum interference, which allows one to implement both electromagnetically induced transparency and electromagnetically induced abs...

Vertical-cavity surface-emitting lasers (VCSELs) are semiconductor lasers that have been extensively studied in recent years since they may be promising for some applications, for example, telecommunications. VCSELs have such important features as high quantum efficiency, a low lasing threshold, and the ability to operate in a single mode. At the s...

We present a procedure for the measurement of quadrature components of an electromagnetic field in the far-field as an alternative to the traditional approach based on the homodyne detection (HD) technique. For this, we suggest to use coherent sources such as phase-locked lasers or optical parametric oscillators operating above threshold. Then, we...

## Projects

Project (1)

Theoretical research on high-speed broadband quantum memory on the base of the tripod-type cold atomic ensemble.