Natalia Korolkova | University of St Andrews (original) (raw)

Papers by Natalia Korolkova

Research paper thumbnail of Weak Values and Continuous-Variable Entanglement Concentration

We demonstrate a general weak measurement model which allows Gaussian preserving entanglement con... more We demonstrate a general weak measurement model which allows Gaussian preserving entanglement concentration of the two mode squeezed vacuum. The power of this simple and elegant protocol is through the constraints it places on possible ancilla states and measurement strategies that will allow entanglement concentration. In particular, it is shown how previously discovered protocols of this kind emerge as special examples of the general model described here. Finally, as evidence of its utility, we use it to provide another novel example of such a protocol.

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Research paper thumbnail of Quantum discord from system-environment correlations

In an initially uncorrelated mixed separable bi-partite system, quantum correlations can emerge u... more In an initially uncorrelated mixed separable bi-partite system, quantum correlations can emerge under the action of a local measurement or local noise [A. Streltsov, H. Kampermann, and D. Bruß, Phys. Rev. Lett. 107, 170502 (2011)]. We analyze this counter-intuitive phenomenon using quantum discord as a quantifier. We then relate changes in quantum discord to system-environment correlations between the system in a mixed state and some purifying environmental mode using the Koashi-Winter inequality. On this basis, we suggest an interpretation of discord as a byproduct of transferring entanglement and correlations around the different subsystems of a global pure state.

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Research paper thumbnail of Design of the coherent diffusive photon gun for generating non-classical states

We suggest and discuss a concept of deterministic integrated source of non-classical light based ... more We suggest and discuss a concept of deterministic integrated source of non-classical light based on the coherent diffusive photonics, a coherent light flow in a system of dissipatively coupled waveguides. We show how this practical quantum device can be realized with a system of single-mode waveguides laser-inscribed in nonlinear glass. We describe a hierarchy of models, from the complete multi-mode model of the waveguide network to the single mode coupled to a bath, analyze the conditions for validity of the simplest single-mode model and demonstrate feasibility of the generation of bright sub-Poissonian light states merely from a coherent input. Notably, the generation of non-classical states occurs at the initial stages of the dynamics, and can be accounted for in the linear model that allows us to circumvent the prohibiting computational complexity of the exact full quantum representation.

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Research paper thumbnail of Entanglement distribution: New concepts and the continuous variable toolbox

Přednaska se týkala výzkumu ve třech oblastech, který probihal ve skupině kvantove optiky na univ... more Přednaska se týkala výzkumu ve třech oblastech, který probihal ve skupině kvantove optiky na univerzitě v St Andrews ve Skotsku: (1) Generovani negaussovských stavů pomoci tzv. Kerrovy nelinearity, (2) koncentrace kvantove provazanosti pomoci slabých měřeni a (3) distribuce provazanosti pomoci separabilniho stavu.

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Research paper thumbnail of Bright quantum-entangled pulses

Summary form only given. We report on a scheme for the generation of bright entangled light beams... more Summary form only given. We report on a scheme for the generation of bright entangled light beams aimed at quantum communication applications. The experiment is based on the recently proposed theme where two intense independently squeezed light fields interfere to produce multi-photon entangled light fields. An asymmetric fibre Sagnac interferometer is used.

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Research paper thumbnail of Kerr-effect induced correlations of optical fiber solitons and the impact of phase control

Frontiers in Optics, 2003

1. Summary The non-linear interaction between light pulses and matter depends on the amplitude an... more 1. Summary The non-linear interaction between light pulses and matter depends on the amplitude and phase distribution within the pulse. At equilibrium the non-linear dynamics of optical pulses in fibers produces solitons which are stable in a classical regime. In contrast, the quantum ...

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Research paper thumbnail of Reconciliation witness and reliability of a quantum atmospheric channel

Physica Scripta, 2013

ABSTRACT The reliability of free-space quantum communication is strongly affected by turbulence p... more ABSTRACT The reliability of free-space quantum communication is strongly affected by turbulence present in atmospheric channels. The signal is randomly distorted or gets lost due to the fluctuations of atmospheric refractive index. We consider quantum communication with coherent and squeezed states and derive the fidelities for quantum states transmitted through such a free-space channel. We show that the fidelity can be significantly enhanced by postselecting high transmission events at the expense of decreasing transmission bit rate. Next, we introduce the witness function that characterizes the reliability of the reconciliation procedure between the communicating parties. Based on this measure, we suggest the receiver strategy that further improves the reconciliation quality.

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Research paper thumbnail of Formation and conversion of the polarization-squeezed light

Journal of Modern Optics, 1996

We consider polarization-squeezed (PS) light generation in anisotropic Kerr medium. The fluctuati... more We consider polarization-squeezed (PS) light generation in anisotropic Kerr medium. The fluctuations of the Stokes parameter either S2 or S3 are suppressed in PS light. We show the possibility to transform PS light into light with sub-Poissonian statistics by linear conversion (phase plate and analyser). The quantum properties of the second harmonic (SH) generated by frequency doubling of the PS light are investigated.

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Research paper thumbnail of Continuous-variable quantum digital signatures over insecure channels

Physical Review A, 2019

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Research paper thumbnail of Quantum correlations in separable multi-mode states and in classically entangled light

Reports on Progress in Physics

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Research paper thumbnail of Dissipatively coupled waveguide networks for coherent diffusive photonics

Nature communications, Dec 4, 2017

A photonic circuit is generally described as a structure in which light propagates by unitary exc... more A photonic circuit is generally described as a structure in which light propagates by unitary exchange and transfers reversibly between channels. In contrast, the term 'diffusive' is more akin to a chaotic propagation in scattering media, where light is driven out of coherence towards a thermal mixture. Based on the dynamics of open quantum systems, the combination of these two opposites can result in novel techniques for coherent light control. The crucial feature of these photonic structures is dissipative coupling between modes, via an interaction with a common reservoir. Here, we demonstrate experimentally that such systems can perform optical equalisation to smooth multimode light, or act as a distributor, guiding it into selected channels. Quantum thermodynamically, these systems can act as catalytic coherent reservoirs by performing perfect non-Landauer erasure. For lattice structures, localised stationary states can be supported in the continuum, similar to compacton...

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Research paper thumbnail of Free-Space Quantum Signatures Using Heterodyne Measurements

Physical Review Letters, 2016

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Research paper thumbnail of Nonclassical states of the second optical harmonic in the presence of self-action

2Nd International Workshop on Squeezed States and Uncertainty Relations, Mar 1, 1993

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Research paper thumbnail of Cross-Kerr effective Hamiltonian for a non-resonant four-level atom

Eprint Arxiv 0711 1808, Nov 1, 2007

We derive a cross-Kerr type effective Hamiltonian for the four-level atom interacting with three ... more We derive a cross-Kerr type effective Hamiltonian for the four-level atom interacting with three electromagnetic fields in the N-configuration. When the atom has relaxed into the ground state a cross-Kerr nonlinearity arises between two weak probe fields. As a development on earlier work we show in general that the atom will also display a linear and self-Kerr response. However, if certain resonance conditions are satisfied then the linear and self-Kerr interactions will vanish. The electrical susceptibilities of the probe transitions are also explored and it is shown that a large, pure cross-Kerr nonlinearity can be generated with vanishing absorption of both probe fields.

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Research paper thumbnail of Polarization squeezing and nonclassical properties of light (7 pages)

Physical Review a Atomic Molecular and Optical Physics, 2006

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Research paper thumbnail of Weak values and entanglement concentration

AIP Conference Proceedings, 2009

Weak values and entanglement concentration. [AIP Conference Proceedings 1110, 9 (2009)]. David Me... more Weak values and entanglement concentration. [AIP Conference Proceedings 1110, 9 (2009)]. David Menzies, Natalia Korolkova. Abstract. Weak measurements are a special class of indirect measurements where the signal system ...

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Research paper thumbnail of Entangling the Whole by Beam Splitting a Part

Physical Review Letters, 2015

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Research paper thumbnail of 26 Quantum Structure of Fiber Solitons and Quantum Communication

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Research paper thumbnail of Amplitude squeezing in asymmetric fiber Sagnac interferometer operating on two polarizations

m with a pulse width around 130 fs. The nonlinear Kerr effect dominates the propagation owing to ... more m with a pulse width around 130 fs. The nonlinear Kerr effect dominates the propagation owing to the high peak power of up to 3.5kW. A half wave plate aligns the linearly po- larized light coming from the laser at a 45 angle with respect to the two main axes of the fiber ensuring an equal energy distribution between them.

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Research paper thumbnail of Direct experimental text of non-separability and other quantum techniques using continuous variables of light

We present schemes for the generation and evaluation of continuous variable entanglement of brigh... more We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give a brief overview of a variety of optical techniques and quantum communi- cation applications on this basis. A new entanglement-based quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the relative interference phase which

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Research paper thumbnail of Weak Values and Continuous-Variable Entanglement Concentration

We demonstrate a general weak measurement model which allows Gaussian preserving entanglement con... more We demonstrate a general weak measurement model which allows Gaussian preserving entanglement concentration of the two mode squeezed vacuum. The power of this simple and elegant protocol is through the constraints it places on possible ancilla states and measurement strategies that will allow entanglement concentration. In particular, it is shown how previously discovered protocols of this kind emerge as special examples of the general model described here. Finally, as evidence of its utility, we use it to provide another novel example of such a protocol.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Quantum discord from system-environment correlations

In an initially uncorrelated mixed separable bi-partite system, quantum correlations can emerge u... more In an initially uncorrelated mixed separable bi-partite system, quantum correlations can emerge under the action of a local measurement or local noise [A. Streltsov, H. Kampermann, and D. Bruß, Phys. Rev. Lett. 107, 170502 (2011)]. We analyze this counter-intuitive phenomenon using quantum discord as a quantifier. We then relate changes in quantum discord to system-environment correlations between the system in a mixed state and some purifying environmental mode using the Koashi-Winter inequality. On this basis, we suggest an interpretation of discord as a byproduct of transferring entanglement and correlations around the different subsystems of a global pure state.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Design of the coherent diffusive photon gun for generating non-classical states

We suggest and discuss a concept of deterministic integrated source of non-classical light based ... more We suggest and discuss a concept of deterministic integrated source of non-classical light based on the coherent diffusive photonics, a coherent light flow in a system of dissipatively coupled waveguides. We show how this practical quantum device can be realized with a system of single-mode waveguides laser-inscribed in nonlinear glass. We describe a hierarchy of models, from the complete multi-mode model of the waveguide network to the single mode coupled to a bath, analyze the conditions for validity of the simplest single-mode model and demonstrate feasibility of the generation of bright sub-Poissonian light states merely from a coherent input. Notably, the generation of non-classical states occurs at the initial stages of the dynamics, and can be accounted for in the linear model that allows us to circumvent the prohibiting computational complexity of the exact full quantum representation.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Entanglement distribution: New concepts and the continuous variable toolbox

Přednaska se týkala výzkumu ve třech oblastech, který probihal ve skupině kvantove optiky na univ... more Přednaska se týkala výzkumu ve třech oblastech, který probihal ve skupině kvantove optiky na univerzitě v St Andrews ve Skotsku: (1) Generovani negaussovských stavů pomoci tzv. Kerrovy nelinearity, (2) koncentrace kvantove provazanosti pomoci slabých měřeni a (3) distribuce provazanosti pomoci separabilniho stavu.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bright quantum-entangled pulses

Summary form only given. We report on a scheme for the generation of bright entangled light beams... more Summary form only given. We report on a scheme for the generation of bright entangled light beams aimed at quantum communication applications. The experiment is based on the recently proposed theme where two intense independently squeezed light fields interfere to produce multi-photon entangled light fields. An asymmetric fibre Sagnac interferometer is used.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Kerr-effect induced correlations of optical fiber solitons and the impact of phase control

Frontiers in Optics, 2003

1. Summary The non-linear interaction between light pulses and matter depends on the amplitude an... more 1. Summary The non-linear interaction between light pulses and matter depends on the amplitude and phase distribution within the pulse. At equilibrium the non-linear dynamics of optical pulses in fibers produces solitons which are stable in a classical regime. In contrast, the quantum ...

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Research paper thumbnail of Reconciliation witness and reliability of a quantum atmospheric channel

Physica Scripta, 2013

ABSTRACT The reliability of free-space quantum communication is strongly affected by turbulence p... more ABSTRACT The reliability of free-space quantum communication is strongly affected by turbulence present in atmospheric channels. The signal is randomly distorted or gets lost due to the fluctuations of atmospheric refractive index. We consider quantum communication with coherent and squeezed states and derive the fidelities for quantum states transmitted through such a free-space channel. We show that the fidelity can be significantly enhanced by postselecting high transmission events at the expense of decreasing transmission bit rate. Next, we introduce the witness function that characterizes the reliability of the reconciliation procedure between the communicating parties. Based on this measure, we suggest the receiver strategy that further improves the reconciliation quality.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Formation and conversion of the polarization-squeezed light

Journal of Modern Optics, 1996

We consider polarization-squeezed (PS) light generation in anisotropic Kerr medium. The fluctuati... more We consider polarization-squeezed (PS) light generation in anisotropic Kerr medium. The fluctuations of the Stokes parameter either S2 or S3 are suppressed in PS light. We show the possibility to transform PS light into light with sub-Poissonian statistics by linear conversion (phase plate and analyser). The quantum properties of the second harmonic (SH) generated by frequency doubling of the PS light are investigated.

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Research paper thumbnail of Continuous-variable quantum digital signatures over insecure channels

Physical Review A, 2019

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Research paper thumbnail of Quantum correlations in separable multi-mode states and in classically entangled light

Reports on Progress in Physics

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Research paper thumbnail of Dissipatively coupled waveguide networks for coherent diffusive photonics

Nature communications, Dec 4, 2017

A photonic circuit is generally described as a structure in which light propagates by unitary exc... more A photonic circuit is generally described as a structure in which light propagates by unitary exchange and transfers reversibly between channels. In contrast, the term 'diffusive' is more akin to a chaotic propagation in scattering media, where light is driven out of coherence towards a thermal mixture. Based on the dynamics of open quantum systems, the combination of these two opposites can result in novel techniques for coherent light control. The crucial feature of these photonic structures is dissipative coupling between modes, via an interaction with a common reservoir. Here, we demonstrate experimentally that such systems can perform optical equalisation to smooth multimode light, or act as a distributor, guiding it into selected channels. Quantum thermodynamically, these systems can act as catalytic coherent reservoirs by performing perfect non-Landauer erasure. For lattice structures, localised stationary states can be supported in the continuum, similar to compacton...

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Research paper thumbnail of Free-Space Quantum Signatures Using Heterodyne Measurements

Physical Review Letters, 2016

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Research paper thumbnail of Nonclassical states of the second optical harmonic in the presence of self-action

2Nd International Workshop on Squeezed States and Uncertainty Relations, Mar 1, 1993

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Research paper thumbnail of Cross-Kerr effective Hamiltonian for a non-resonant four-level atom

Eprint Arxiv 0711 1808, Nov 1, 2007

We derive a cross-Kerr type effective Hamiltonian for the four-level atom interacting with three ... more We derive a cross-Kerr type effective Hamiltonian for the four-level atom interacting with three electromagnetic fields in the N-configuration. When the atom has relaxed into the ground state a cross-Kerr nonlinearity arises between two weak probe fields. As a development on earlier work we show in general that the atom will also display a linear and self-Kerr response. However, if certain resonance conditions are satisfied then the linear and self-Kerr interactions will vanish. The electrical susceptibilities of the probe transitions are also explored and it is shown that a large, pure cross-Kerr nonlinearity can be generated with vanishing absorption of both probe fields.

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Research paper thumbnail of Polarization squeezing and nonclassical properties of light (7 pages)

Physical Review a Atomic Molecular and Optical Physics, 2006

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Research paper thumbnail of Weak values and entanglement concentration

AIP Conference Proceedings, 2009

Weak values and entanglement concentration. [AIP Conference Proceedings 1110, 9 (2009)]. David Me... more Weak values and entanglement concentration. [AIP Conference Proceedings 1110, 9 (2009)]. David Menzies, Natalia Korolkova. Abstract. Weak measurements are a special class of indirect measurements where the signal system ...

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Research paper thumbnail of Entangling the Whole by Beam Splitting a Part

Physical Review Letters, 2015

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Research paper thumbnail of 26 Quantum Structure of Fiber Solitons and Quantum Communication

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Amplitude squeezing in asymmetric fiber Sagnac interferometer operating on two polarizations

m with a pulse width around 130 fs. The nonlinear Kerr effect dominates the propagation owing to ... more m with a pulse width around 130 fs. The nonlinear Kerr effect dominates the propagation owing to the high peak power of up to 3.5kW. A half wave plate aligns the linearly po- larized light coming from the laser at a 45 angle with respect to the two main axes of the fiber ensuring an equal energy distribution between them.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Direct experimental text of non-separability and other quantum techniques using continuous variables of light

We present schemes for the generation and evaluation of continuous variable entanglement of brigh... more We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give a brief overview of a variety of optical techniques and quantum communi- cation applications on this basis. A new entanglement-based quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the relative interference phase which

Bookmarks Related papers MentionsView impact