# Stephen VintskevichTechnology Innovation Institute (TII) | TII · Quantum Research Centre

Stephen Vintskevich

PhD

## About

44

Publications

4,368

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419

Citations

Introduction

Additional affiliations

July 2017 - April 2022

September 2015 - July 2017

## Publications

Publications (44)

The concept of mass for pairs of particles (including photons) is extended for a classical electromagnetic field, for which the difference of the energy and momentum densities is shown to be invariant with respect to Lorentz transformations and interpretable as the mass density of the field.

We show that the concept of the Lorentz-invariant mass of groups of particles can be applied to light pulses consisting of very large but finite numbers of noncollinear photons. Explicit expressions are found for the invariant mass of this manifold of photons for the case of diverging Gaussian light pulses propagating in vacuum. As the found invari...

The difficulty to simulate the dynamics of open quantum systems resides in their coupling to many-body reservoirs with exponentially large Hilbert space. Applying a tensor network approach in the time domain, we demonstrate that effective small reservoirs can be defined and used for modeling open quantum dynamics. The key element of our technique i...

The Hanbury Brown-Twiss (HBT) effect holds a pivotal place in intensity interferometry and gave a seminal contribution to the development of quantum optics. To observe such an effect, both good spectral and timing resolutions are necessary. Most often, the HBT effect is observed for a single frequency at a time, due to limitations in dealing with m...

We introduce a novel super-resolution imaging technique, combining photon distribution analysis and point spread function shaping. Resolving unbalanced point sources with unknown parameters is achieved across diverse photon statistics.

We propose a new approach to quantum-assisted astrometry with the potential to improve their astrometric precision by orders of magnitude. We extend our framework to super-resolution microscopy and sensor networks and demonstrate novel experimental capabilities.

Classical optical interferometry requires maintaining live, phase-stable links between telescope stations. This requirement greatly adds to the cost of extending to long baseline separations and limits on baselines will in turn limit the achievable angular resolution. Here we describe a novel type of two-photon interferometer for astrometry, which...

We present a single-photon-sensitive spectrometer, based on a linear array of 512 single-photon avalanche diodes, with 0.04 nm spectral and 40 ps temporal resolutions. We employ a fast data-driven operation that allows direct measurement of time and frequency for simultaneous single photons. Combining excellent temporal and spectral resolution, our...

We apply the support vector machine (SVM) algorithm to derive a set of entanglement witnesses (EW) to identify entanglement patterns in families of four-qubit states. The effectiveness of SVM for practical EW implementations stems from the coarse-grained description of families of equivalent entangled quantum states. The equivalence criteria in our...

Optical interferometers may not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling long baselines. We developed a new variation of this idea, proposing that photons from two different astronomical sources could be interfered at two decoupled station...

Optical Very-Long-Baseline Interferometers (VLBI), widely used in astronomy, require phase-stable optical links across stations, which impose a limit on baseline distances, and, in turn, limits measurement precision. Here we describe a novel type of two-photon quantum-assisted interferometer, which may allow improvements in precision by orders of m...

We describe a novel type of two-photon interferometer, capable of spectral binning, for quantum-assisted astrometry. We also demonstrated a single-photon spectrometer with spectral and timing resolutions of 0.1 nm and 50 ps, which can be used for this purpose. This work opens new possibilities in future astronomical measurements.

We apply the support vector machine (SVM) algorithm to derive a set of entanglement witnesses (EW) to identify entanglement patterns in families of four-qubit states. The effectiveness of SVM for practical EW implementations stems from the coarse-grained description of families of equivalent entangled quantum states. The equivalence criteria in our...

Optical interferometers may not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling long baselines. We developed a new variation of this idea, proposing that photons from two different astronomical sources could be interfered at two decoupled station...

Currently, quantum reservoir computing is one of the most promising and experimentally accessible techniques for hybrid, quantum-classical machine learning. However, its applications are limited due to practical restrictions on the size of quantum systems and the influence of noise. Here we propose a novel approach to connect two quantum reservoirs...

We propose a novel approach to link multipartite quantum systems - quantum reservoirs into a network to implement quantum reservoir computing. We present the machine learning-based heuristics to optimize performance and information transfer between systems.

We describe a new technique of quantum astrometry, which potentially can improve the resolution of optical interferometers by orders of magnitude. The approach requires fast imaging of single photons with sub-nanosecond resolution, greatly benefiting from recent advances in photodetection technologies. We also describe results of first proof of pri...

Improved determination of photon wave-functions could provide high-resolution observations in the optical, benefiting numerous topics in astrophysics and cosmology. It has been recently suggested that optical interferometers would not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs...

Improved quantum sensing of photon wave-functions could provide high resolution observations in the optical benefiting numerous fields, including general relativity, dark matter studies, and cosmology. It has been recently proposed that stations in optical interferometers would not require a phase-stable optical link if instead sources of quantum-m...

The concept of Lorenz invariant mass and mean propagation velocity have been investigated in detail for various multiphoton wave-packet states of light. Based on photodetection theory and straightforward kinematics, we presented a physically reasonable and at the same time rigorous proof that mean propagation velocity is consistent with the Lorentz...

The uses of a silicon-pixel camera with very good time resolution (∼nanosecond) for detecting multiple, bunched optical photons is explored. We present characteristics of the camera and describe experiments proving its counting capabilities. We use a spontaneous parametric down-conversion source to generate correlated photon pairs, and exploit the...

The uses of a silicon-pixel camera with very good time resolution ($\sim$nanosecond) for detecting multiple, bunched optical photons is explored. We present characteristics of the camera and describe experiments proving its counting capabilities. We use a spontaneous parametric down-conversion source to generate correlated photon pairs, and exploit...

Machine learning methods have proved to be useful for the recognition of patterns in statistical data. The measurement outcomes are intrinsically random in quantum physics, however, they do have a pattern when the measurements are performed successively on an open quantum system. This pattern is due to the system-environment interaction and contain...

Pumping a nonlinear crystal by an intense radiation results in the optical parametric generation of photons
in two modes (the signal and the idler). The quantized electromagnetic field in these modes is described by a
continuous-variable quantum state, which is entangled if the pump is a coherent state produced by a laser. The
signal and the idler...

The Lorentz-invariant mass and mean propagation speed have been found for structured light pulses in a vacuum considered as relativistic objects. We have solved the boundary problem for such widely known field configurations as Gauss, Laguerre–Gauss, Bessel–Gauss, Hermite–Gauss and Airy–Gauss. The pulses were taken as having a temporal envelope of...

The concept of the Lorentz-invariant mass of a group of particles is shown to be applicable to biphoton states formed in the process of spontaneous parametric down conversion. The conditions are found when the Lorentz-invariant mass is related directly with (proportional to) the Schmidt parameter determining a high degree of entanglement of a bipho...

Pumping a nonlinear crystal by an intense radiation results in the optical parametric generation of photons in two modes (the signal and the idler). Quantized electromagnetic field in these modes is described by a continuous-variable quantum state, which is entangled if the pump is a coherent state produced by a laser. The signal and the idler mode...

The concept of the Lorentz-invariant mass of a group of particles is shown to be applicable to biphoton states formed in the process of spontaneous parametric down conversion. The conditions are found when the Lorentz-invariant mass is related directly with (proportional to) the Schmidt parameter $K\gg 1$ determining a high degree of entanglement o...

Machine learning methods have proved to be useful for the recognition of patterns in statistical data. The measurement outcomes are intrinsically random in quantum physics, however they do have a pattern when the measurements are performed successively on an open quantum system. This pattern is due to the system-environment interaction and contains...

Machine learning methods have proved to be useful for the recognition of patterns in statistical data. The measurement outcomes are intrinsically random in quantum physics, however they do have a pattern when the measurements are performed successively on an open quantum system. This pattern is due to the system-environment interaction and contains...

Density matrices of pure multiphoton Fock polarization states and of arising from them reduced density matrices of mixed states are expressed in similar ways in terms of matrices of correlators defined as averaged products of equal numbers of creation and annihilation operators. Degree of entanglement of considered states is evaluated for various c...

The difficulty to simulate the dynamics of open quantum systems resides in their coupling to many-body reservoirs with exponentially large Hilbert space. Applying a tensor network approach in the time domain, we demonstrate that effective small reservoirs can be defined and used for modelling open quantum dynamics. The key element of our technique...

The difficulty to simulate the dynamics of open quantum systems resides in their coupling to many-body reservoirs with exponentially large Hilbert space. Applying a tensor network approach in the time domain, we demonstrate that effective small reservoirs can be defined and used for modelling open quantum dynamics. The key element of our technique...

We consider regimes of spontaneous parametric down-conversion, both noncollinear and nondegenerate in frequencies. Parameters characterizing degrees of noncollinearity and of nondegeneracy are defined, and they are shown to be not independent of each other. At a given degree of nondegeneracy the emitted photons are shown to propagate along two diff...

We consider regimes of Spontaneous Parametric Down-Conversion both noncollinear and nondegenerate in frequencies. Parameters characterizing degrees of noncollinearity and of nondgeneracy are defined, and they are shown to be not independent of each other. At a given degree of nondegeneracy the emitted photons are shown to propagate along two differ...

We present novel and simple estimation of a minimal dimension required for an effective reservoir in open quantum systems. Using a tensor network formalism we introduce a new object called a reservoir network (RN). The reservoir network is the tensor network in the form of a Matrix Product State, which contains all effects of open dynamics. This ob...

The well-known Hong-Ou-Mandel effect is revisited. Two physical reasons are discussed for the effect to be less pronounced or even to disappear: differing polarizations of photons coming to the beamsplitter and delay time of photons in one of two channels. For the latter we use the concepts of biphoton frequency and temporal wave functions dependin...

The mean velocity of a finite-size short light pulse in a far zone is defined as the vectorial sum of velocities of all rays forming the pulse. Because of diffraction, the mean pulse velocity defined in this way is always somewhat smaller than the speed of light. The conditions are found when this slowing-down effect is sufficiently pronounced to b...

The concept of the Lorentz-invariant mass of groups of photons is shown to be applicable to classical light pulses with finite sizes and duration. Diffraction of light, providing non-collinearity of the photon motion in pulses, provides also nonzero values of their Lorentz-invariant masses. By considering light pulses as relativistic objects we fin...