Quantum Information Science is a rapidly growing interdisciplinary field, at the intersection
of physics, mathematics and computer science. It employs the fundamental properties of quantum systems
— coherent superposition, entanglement and quantum parallelism — to advance Quantum Technologies
and realize practical devices and applications for quantum simulations and computing,
communication and cryptography, sensing and metrology, microscopic engines and refrigerators.

The members of our Group have been actively involved in research and teaching in Quantum Information Science,
with the goal of advancing Quantum Technologies in Armenia.

## Brief description of our research interests and expertise

*Armen Allahverdyan*

**Quantum thermodynamics** studies energy and information
flows on the micro/nano scale. In essence it uses microscopic and
mesoscopic quantum physics to describe systems traditionally treated
with statistical physics and thermodynamics. Its aims are both to
understand the emergence of fundamental properties of thermodynamic
systems from quantum principles, and to design and implement quantum
motors, engines and refrigerators for various practical applications.
Emphasizing a joint description of energy (work, efficiency, heat,
temperature) and information (purity, entropy, entanglement,
correlations) is what distinguishes this subject in the broader context
of quantum information science. We were among the pioneers of quantum
thermodynamics [1], while recently we have been working on bringing
quantum thermodynamic ideas into classical physics [2,3,4,5].

**Quantum foundations** is a research subject that identifies
and scrutinizes open conceptual problems of quantum mechanics (also from
within quantum mechanics) and points directions towards more general
(subquantum) theories. We studied two types of such conceptual problems.
First, quantum measurement [6], viz. how the classical probability
space emerges for measurement results, Born’s rule is explained etc.
Second, the problem of joint probability for non-commuting observables,
e.g. coordinate and momentum. This problem is closely related to almost
any other conceptual issue of quantum mechanics, from Bell’s
inequalities (which can be reformulated as solely a joint probability
issue) to quantum tomography, consistent histories, Wigner functions,
weak measurements etc. Here we introduced the concept of imprecise
quantum, joint probability and worked out its consequences e.g. for the
(non)locality issue [7,8].

*Hakob Avetisyan*

We are interested in Quantum Information Theory, near-term applications of Quantum Computing, Quantum Algorithms, Quantum Simulation, Error Mitigation and Distributed Quantum Computing. We have co-founded in 2018 the quantum computing lab Gate42 with the mission to get closer to solving real world problems with quantum computers. We program quantum computers in different languages, such as IBM’s qiskit, Rigetti’s pyquil, DWave’s ocean and Xanadu’s pennylane/strawberrifields, and we have implemented various algorithms on quantum information theory, near term applications of quantum computing and quantum simulation. Some of our projects are:

Quantum Error Mitigation with PyQuil: Implementation of the "extrapolation to the zero noise limit" method of quantum error mitigation as a python package.

IBM Quantum Challenge 2019 Hackathon: A graph coloring problem solution with Grover's algorithm.

Quantum Futures Hackathon 2019 at CERN: A simulated network of quantum computers with a web interface for running distributed programs on the network.

You can follow our progress on github, including our presentation at Rigetti QC Hackathon (Berkley) and our unitary.fund grant program run by Will Zeng.

Our research interests also include the study of propagation of
two photon light in the atmosphere [1,2], which is relevant to free
space quantum communication (including larger-alphabet encoding) and
various quantum key distribution protocols.

*Karen Hovhannisyan*

Our research interests mostly lie within **quantum thermodynamics** and **quantum metrology**, extensively using tools and concepts of **quantum information science**.

The laws of thermodynamics are omnipresent in virtually all areas
of physics, serving as guiding principles both in foundational and
practical matters. Understanding if and how these laws extend to the
realm of small quantum systems is both a fascinating theoretical
undertaking and key for emerging quantum technologies, where both
quantum and thermal effects will inevitably play significant roles. My
work focuses on thermal machines [1, 2, 3] and the interplay between
quantum-informational resources, such as entanglement and contextuality,
and thermodynamic resources, such as work and current [1, 2, 5, 6].

With the advancement of quantum technologies, accurate probing of
thermodynamic quantities and parameters of nanometer-sized systems is
of paramount importance. This includes the problem of measuring figures
of merit — such as work, heat, current, etc — of thermodynamic devices
[2, 4], as well as measuring parameters, such as temperature. My focus
in the latter has been noninvasive thermometry of ultracold quantum
many-body systems, where one tries to avoid deteriorating effects of
quantum measurements [7, 8].

*David Karakhanyan*

We mostly deal with **mathematical physics of integrable models**.
This rich field started with the exact solution of the two-dimensional Ising model,
and traditionally applied to quantum many-body physics. Recent interesting applications
include quantum information processing, e.g., via topologically protected states
and new schemes for universal quantum computation.

We have studied integrable models such as one-dimensional spin chains and Calogero model,
Bethe Ansatz, Yangians of orthogonal and symplectic groups, construction of universal
R-matrices and Baxter operators for various (super) Lie algebras, as well as representations
of Yangian and deformed Lie algebras. We are also interested in classical field theories,
string theory, and the high-energy limit of quantum chromodynamics (Regge and Björken
approximations).

*David Petrosyan*

We work on several problems related to the physical implementations of **quantum simulations** and **quantum information processing**.
We study realizations of various spin lattice models using cold atoms
in optical lattices or arrays of microtraps. Controllable interatomic
interactions are provided by laser excitation and de-excitation of the
strongly interacting Rydberg states. Relaxations can also be included in
these systems in a controllable way to simulate and study coherent and
dissipative dynamics of few- and many-body systems and their different
phases [1].

Spin lattices can also be realized by other systems, such as the
ion traps and arrays of coupled superconducting qubits. We explore
superconducting circuits to implement functional logical elements, such
as quantum spin transistors, diodes and routers that can be incorporated
in the future integrated quantum devices [2,3].

In collaboration with experimentalists, we explore interfaces
between the microwave and optical photons using coherent atomic
ensembles trapped on superconducting atoms chips [4]. Our theoretical
and experimental efforts also aim to realize long-range quantum gates
between the atoms in microwave cavities [5], and to quantify and
characterize the Rydberg blockade in macroscopic atomic ensembles. Our
broader goal is to realize functional, **hybrid quantum devices** incorporating the advantageous properties of quantum-optical and solid-state systems [6].

*Hayk Sargsyan*

I am interested in quantum algorithms, foundational questions of quantum mechanics,
and quantum field theories and their investigation in nano-systems as well as on cosmological scales.

As a member of the quantum computing lab Gate42,
I use mathematical tools to develop realistic continuous variable quantum algorithms.
I also contribute to various quantum packages, such as IBM Qiskit, OpenFermion and StrawberryFields.

I study quantum fields (scalar, electromagnetic and fermionic) in spacetimes with non-trivial topological properties,
e.g., compactified dimensions, and/or on the background of gravitational fields. We are mostly interested in the
development of analytical methods, so that more insight can be gained into the quantum field theory on the background
of curved spacetime compared to numerical methods. Several foundational questions arise in these models, such as the
Aharnonov-Bohm effect, persistent currents, and non-trivial effects of boundaries, which we investigate.
The general analytical methods that we develop in our research have wide spectrum of applications ranging
from high dimensional cosmological models of the Universe [1,2] to low dimensional nano-systems [3], such as nano-rings,
nano-cones and topological insulators.

## Outreach

We actively popularize the field of quantum information science in Armenia through seminars and lecture courses, both at the introductory level, and on advanced topics, such as Quantum Statistical Thermodynamics and Quantum Optics and Quantum Information. Our Guide and Tutorials on various quantum computing algorithms can be helpful to the researchers who want to enter the area of Quantum Computation and Quantum Information Science. Hakob teaches a course on “Introduction to quantum computing” at the American University of Armenia as a hands-on course to program a quantum computer. We encourage other Armenian universities to offer courses on quantum computing, quantum cryptography, quantum optics, special topics in modern quantum mechanics and other emerging topics in quantum information science. Teaching these subjects will better prepare Armenian students for the Second Quantum Revolution. If you are a student or a researcher interested in quantum technologies, please contact us.

## Selected publications

#### A.E. Allahverdyan

- A.E. Allahverdyan and Th.M. Nieuwenhuizen,
*Extraction of work from a single thermal bath in the quantum regime*, Phys. Rev. Lett.**85**, 1799, (2000). - A.E. Allahverdyan and D. Karakhanyan,
*Defining the work done on an electromagnetic field*, Phys. Rev. Lett.**121**, 240602 (2018). - E. Allahverdyan and N.H. Martirosyan,
*Free energy for non-equilibrium quasi-stationary states*, EPL (Europhysics Letters)**117**, 50004 (2017). - E. Allahverdyan, S.G. Babajanyan, N.H. Martirosyan, and A. V. Melkikh,
*Adaptive Heat Engine*, Phys. Rev. Lett.**117**, 30601 (2016). - A.E. Allahverdyan,
*Work-extraction from fluid flow: the analogue of Carnot's efficiency*, arXiv:2002.09276 [physics.flu-dyn] (2020). - E. Allahverdyan, R. Balian, and Th. M. Nieuwenhuizen,
*Understanding quantum measurement from the solution of dynamical models,*Physics Reports,**525**, 1-166 (2013). - E. Allahverdyan and A. Danageozian,
*Quantum non-locality co-exists with locality*, EPL (Europhysics Letters),**122**, 40005 (2018). - A.E. Allahverdyan and A. Danageozian,
*Excluding joint probabilities from quantum theory*, Phys. Rev. A**97**, 030102(R) (2018).

#### H. Avetisyan

- H. Avetisyan, C. H. Monken,
*Mode analysis of higher-order transverse-mode correlation beams in turbulent atmosphere*, Opt. Lett.**42**, 101, (2017). - H. Avetisyan, C. H. Monken,
*Higher order correlation beams in atmosphere under strong turbulence conditions*, Opt. Express**24**, 2318 (2016).

#### K.V. Hovhannisyan

- A. Pozas-Kerstjens, E.G. Brown, K.V. Hovhannisyan, New J. Phys.
**20**, 043034 (2018). - K.V. Hovhannisyan, A. Imparato, New J. Phys.
**21**, 052001 (2019). - K.V. Hovhannisyan, F. Barra, A. Imparato, arXiv:2001.07696 (2020).
- M. Perarnau-Llobet, E. Bäumer, K.V. Hovhannisyan, M. Huber, A. Acín, Phys. Rev. Lett.
**118**, 070601 (2017). - K.V. Hovhannisyan, M. Perarnau-Llobet, M. Huber, A. Acín, Phys. Rev. Lett.
**111**, 240401 (2013). - M. Perarnau-Llobet, K.V. Hovhannisyan, M. Huber, P. Skrzypczyk, N. Brunner, A. Acín, Phys. Rev. X
**5**, 041011 (2015). - L.A. Correa, M. Perarnau-Llobet, K.V. Hovhannisyan, S. Hernández-Santana, M. Mehboudi, A. Sanpera, Phys. Rev. A
**96**, 062103 (2017). - K.V. Hovhannisyan, L.A. Correa, Phys. Rev. B
**98**, 045101 (2018).

#### D. Karakhanyan

- D.Karakhanyan, R.Kirschner,
*Spinorial R operator and Algebraic Bethe Ansatz*, Nucl. Phys. B**951**, 102-126 (2020). - D.Karakhanyan, R.Kirschner,
*Orthogonal and symplectic Yangians - linear and quadratic evaluations*, Nucl. Phys. B**933**, 14-39 (2018). - J. Fuksa, A.P. Isaev, D. Karakhanyan, R. Kirschner,
*Yangians and Yang–Baxter R-operators for ortho-symplectic superalgebras*, Nucl. Phys. B**917**, 44-85 (2017). - A.P. Isaev, D. Karakhanyan, R. Kirschner,
*Orthogonal and symplectic Yangians and Yang-Baxter R-operators*, Nucl. Phys. B**904**, 124-147 (2016). - T. Hakobyan, D. Karakhanyan, O. Lechtenfeld,
*The structure of invariants in conformal mechanics*, Nucl. Phys. B**886**, 399-420 (2014).

#### D. Petrosyan

- D. Petrosyan,
*Quantum gates and simulations with strongly interacting Rydberg atoms,*ERCIM News**112**, 31 (2018) - S. Christensen, S. E. Rasmussen, D. Petrosyan, N. T. Zinner,
*Coherent router for quantum networks with superconducting qubits*, Phys. Rev. Research**2**, 013004 (2020) - V. Marchukov, A. G. Volosniev, M. Valiente, D. Petrosyan, N. T. Zinner,
*Quantum spin transistor with a Heisenberg spin chain,*Nature Commun.**7**, 13070 (2016) - D. Petrosyan, K. Mølmer, J. Fortágh, M. Saffman,
*Microwave to optical conversion with atoms on a superconducting chip,*New J. Phys.**21**, 073033 (2019) - L. Sarkany, J. Fortagh, D. Petrosyan,
*Long-range quantum gate via Rydberg states of atoms in a thermal microwave cavity,*Phys. Rev. A**92**, 030303(R) (2015) - G. Kurizki, P. Bertet, Y. Kubo, K. Mølmer, D. Petrosyan, P. Rabl, J. Schmiedmayer,
*Quantum technologies with hybrid systems*, PNAS**112**, 3866 (2015)

#### Hayk Sargsyan

- S. Bellucci, A. A. Saharian, H. G. Sargsyan, and V. V. Vardanyan, Phys. Rev. D
**101**, 045020 (2020). - A. A. Saharian, H. G. Sargsyan, Astrophysics
**61**, 375-390 (2018) . - S. Bellucci, I. Brevik, A. A. Saharian, H. G. Sargsyan, Eur. Phys. J. C
**80**, 281 (2020) .