Igor Mekhov
Igor Mekhov
Visiting Academic
I have been a Head of Theory Group at Oxford since 2011 (cf. the Research Group tab on this page for further details) and worked at the University Paris-Saclay and St. Petersburg State University, while being a Visiting Academic in Oxford.
My main research interest is focused on the theoretical study of the ultimate quantum level of the light-matter interaction. This field touches several disciplines such as quantum optics, ultracold atoms, condensed matter physics, quantum information processing, etc.
See the RESEARCH TABS on this web-page for further details.
RECENT PAPERS:
Phys. Rev. Lett. (2020): Feedback-induced quantum phase transitions, beyond the dissipative ones
Quantum rock 'n' roll APS coverage,
Phys. Rev. Lett. (2020),
arXiv:2003.00191 (2020),
Phys. Rev. Lett.-1 (2015), Phys. Rev. Lett.-2 (2015), New J. Phys. (2015), Phys. Rev. A (2015), Atoms (2015), Scientific Reports (2016), New J. Phys.-1 (2016), Phys. Rev. A-1 (2016), Phys. Rev. A-2 (2016), Phys. Rev. A-3 (2016), Phys. Rev. A-4 (2016), arXiv:1601.02230, New J. Phys.-2 (2016), Optica (OSA) (2016), Scientific Reports (2017).
A REVIEW PAPER is available at Journ. Phys. B 45, 102001 (2012) (arXiv:1203.0552)
RECENT RESULTS:
- We show that applying feedback to a quantum system induces phase transitions beyond the dissipative ones: the feedback-induced phase transitions (FPT). Feedback enables controlling essentially quantum properties of the transition, i.e., tuning its universality class via the critical exponents. Feedback provides the non-Markovianity and nonlinearity to the hybrid quantum-classical system, and enables simulating effects similar to spin-bath problems and Floquet time crystals with tunable long-range (long-memory) interactions.
- We develop a concept of "quantum optical lattices," where the quantized light creates fully quantum and dynamical trapping potential for ultracold bosons and fermions.
- We have introduced the quantum measurement into a many-body system. We have shown that the quantum backaction of weak (non-projective) measurement can effeciently compete with unitary dynamics, thus, constituting a novel source of the competitions in many-body systems. This leads to a plethora of novel effects such as the giant oscillations at single quantum trajectories, long-range correlated pair tunneling, Raman-like virtual transitions in quantum Zeno subspaces, measurement-induced protection and break-up of fermion pairs, and measurement-induced antiferromagnetic orders.
- We have suggested quantum simulations based on the collective enhancement of light-matter interaction. We demonstrated the emergence of not only density orders (e.g., density waves and supersolids), but also the orders of matter-wave coherences (bond orders). This is well beyond predictions of standard Dicke and Bose-Hubbard models.
PhD THESES:
W. Kozlowski. Competition between Weak Quantum Measurement and Many-Body Dynamics in Ultracold Bosonic Gases. PhD Thesis, Oxford (2017). ORA link 1. ORA link 2.
G. Mazzucchi. Conditional Many-Body Dynamics and Quantum Control of Ultracold Fermions and Bosons in Optical Lattices Coupled to Quantized Light. PhD Thesis, Oxford (2017). ORA link 1. ORA link 2.
RESEARCH HIGHLIGHTS
Phys. Rev. Lett. (2020):
We show that applying feedback to a quantum system induces phase transitions beyond the dissipative ones: the feedback-induced phase transitions (FPT). Feedback enables controlling essentially quantum properties of the transition, i.e., tuning its universality class via the critical exponents. Feedback provides the non-Markovianity and nonlinearity to the hybrid quantum-classical system, and enables simulating effects similar to spin-bath problems and Floquet time crystals with tunable long-range (long-memory) interactions.
arXiv:2003.00191 (2020):
We show that the feedback phase transition leads to the self-organization of ultracold atoms even without a cavity.
Phys. Rev. A (2015):
The light is not only sensitive to the density correlations, but also reflects the matter-field interference at its shortest possible distance in an optical lattice. Light scattering distinguishes all quantum phases in the Bose Glass - Mott insulator - superfluid phase transition.
Phys. Rev. Lett.-1 (2015):
We have shown, how to generate multiple spatial modes of matter fields using the quantum measurement. The modes have nontrivial spatial overlap, display genuine multipartite entanglement, and can be used for measurement and detection of the entanglement in quantum gases. We demonstrate non-Gaussian generalizations of multimode squeezed, parametric down-conversion, and Dicke states.
Phys. Rev. Lett.-2 (2015):
We demonstrated novel phase transitions solely due to the quantum light-matter correlations in a quantum optical lattice. The competition between light-field and matter-field coherences leads to novel phases (e.g. delocalized dimers), beyond density-induced orders such as multimode generalizations of density waves and supersolid states.
New J. Phys. (2015):
We demonstrated that light scattered from novel phases of atoms in quantum optical lattices has essentially nonclassical properties (e.g. squeezing).
Atoms (2015), Special Issue:
We considered quantum nondemolition measurement of many-body states of strongly interacting and non-interacting fermions in optical lattices, and demonstrated the measurement-induced entanglement of spin components and generation of macroscopic superposition states on a lattice. We showed that the quadrature measurements can produce Schrödinger cat states, which are more robust with respect to photon losses, than those obtained by the photon number detection. We also showed that quantum optical lattices generated in a cavity change quantum phases of ultracold bosons.
Phys. Rev. A-1 (2016):
We presented a general framework to describe the competition between global quantum measurement and standard local processes (tunneling and on-site interaction) in a strongly correlated many-body system. We demonstrated the following new phenomena: design of nonlocal spatially structured environment for otherwise closed many-body system, long-range correlated tunneling, nonlocal quantum Zeno effect, generation of multimode Schrödinger cat states, break-up and protection of strongly interacting fermion pairs.
Phys. Rev. A-2 (2016):
We suggested a novel type of quantum simulators based on the collective enhancement of light-matter interactions.
New J. Phys.-1 (2016):
We predicted a nontrivial type of dynamics resulting from the novel competition between the quantum backaction of weak measurement and unitary many-body (or multimode) dynamics.
Phys. Rev. A-3 (2016):
We have extended the notion of quantum Zeno dynamics in the realm of non-Hermitian processes. Moreover, we presented an unconventional scenario for quantum Zeno dynamics: a system evolves within a Zeno subspace thanks to Raman-like transitions via virtual states outside that subspace. This corresponds to a rather strong, but not projective quantum measurement.
Scientific Reports (2016):
We demonstrated how the quantum backaction of weak continuous measurement can lead to the generation of antiferromagnetic order and density modulations in the system of ultracold fermions in optical lattices.
Phys. Rev. A-4 (2016):
We demonstrated that joining the ideas of quantum measurement and quantum optical lattices can broaden the field of quantum simulations, allowing simulating numerous models such as superexchange interactions, multispecies Dicke model, pair creation and annihilation, dynamical gauge fields, etc.
arXiv:1601.02230:
We demonstrated that the quantum feedback control can strongly influence the stability region of a BEC trapped inside a cavity. Moreover, it can be used to precisely position a BEC in space and tune the phase of the generated light.
New J. Phys.-2 (2016):
We showed that the emergent global bond order (i.e. the self-organization of matter-wave coherences, rather than densities) is linked to the valence bond solids (VBS). This opens a novel avenue for global quantum simulations, in particular, of high-Tc superconductors.
Optica (OSA) (2016):
We have described the quantum feedback control of novel many-body states, which appear as a result of the competition between the weak measurement backaction and many-body dynamics: multimode density waves and supersolids, antiferromagnetic and NOON states.
Scientific Reports (2017):
Instead of coupling light to the atomic on-site density, we propose a method of coupling directly to the matter-phase-related variables. This constitutes a novel type of quantum measurements and projections, thus generalizing the standard measurement postulate for the case of competition between the weak measurement backaction and system's own dynamics.
Curriculum Vitae
For a formal summary of my research and publications cf. my CV.
Quantum optics of ultracold quantum gases
RECENT PAPERS:
Phys. Rev. Lett. (2020): Feedback-induced quantum phase transitions, beyond the dissipative ones
Quantum rock 'n' roll APS coverage,
Phys. Rev. Lett. (2020),
arXiv:2003.00191 (2020),
Phys. Rev. Lett.-1 (2015), Phys. Rev. Lett.-2 (2015), New J. Phys. (2015), Phys. Rev. A (2015), Atoms (2015), Scientific Reports (2016), New J. Phys.-1 (2016), Phys. Rev. A-1 (2016), Phys. Rev. A-2 (2016), Phys. Rev. A-3 (2016), Phys. Rev. A-4 (2016), arXiv:1601.02230, New J. Phys.-2 (2016), Optica (OSA) (2016), Scientific Reports (2017).
A REVIEW PAPER is available at Journ. Phys. B 45, 102001 (2012) (arXiv:1203.0552)
My current research is focused on theoretical quantum optics of ultracold degenerate gases, where the quantum natures of both light and matter play key roles. Joining the paradigms of two fields of modern physics, cavity QED and ultracold quantum gases, will enable conceptually new investigations of the light-matter interaction at the ultimate quantum level.
We have proposed theoretical models for such phenomena, which can be tested experimentally in the nearest future. (Nature Phys. 2007, Phys. Rev. Lett. 2007, 2009, 2011, 2015, etc.)
This research includes the following areas
- quantum optics, e.g., cavity quantum electrodynamics (QED),
- Bose-Einstein condensation (BEC),
- ultracold gases in optical lattices,
- laser cooling,
- condensed matter physics of strongly correlated systems,
- nanophotonics,
- etc.
Phys. Rev. Lett. (2020):
- We have shown that applying feedback to a quantum system induces phase transitions beyond the dissipative ones: the feedback-induced phase transitions (FPT). Feedback enables controlling essentially quantum properties of the transition, i.e., tuning its universality class via the critical exponents. Feedback provides the non-Markovianity and nonlinearity to the hybrid quantum-classical system, and enables simulating effects similar to spin-bath problems and Floquet time crystals with tunable long-range (long-memory) interactions.
arXiv:2003.00191 (2020):
We show that the feedback phase transition leads to the self-organization of ultracold atoms even without a cavity.
- We have formulated the quantum non-demolition (QND) measurement schemes to observe the properties of many-body atomic states detecting scattered light. Different many-body characteristics beyond the density-density correlations can be obtained by quantum optical methods. (Nature Physics (2007), Phys. Rev. Lett. (2007), Phys. Rev. A (2007), Laser Physics (2009))
- Those methods have been recently applied to ultracold polar molecules. (Phys. Rev. Lett. (2011), Phys. Rev. A (2011), Laser Physics (2013))
In a recent paper (Phys. Rev. A (2015)), we proved that light is not only sensitive to the density correlations, but also reflects the matter-field interference at its shortest possible distance in an optical lattice. We also showed, how to distinguish the Bose Glass, Mott insulator and superfluid phases.
- We suggested to use the entanglement between the light and motion of ultracold atoms to prepare the nonclassical many-body states exploiting the quantum nature of the measurement process (measurement back-action). The preparation of number squeezed and Schrödinger cat states was demonstrated. (Phys. Rev. Lett. (2009), Phys. Rev. A (2009), Laser Physics (2010), Laser Phys. (2011))
In a recent paper (Phys. Rev. Lett.-1 (2015)), we have shown, how to generate multiple spatial modes of matter fields using the quantum measurement. The modes have nontrivial spatial overlap, display genuine multipartite entanglement, and can be used for measurement and detection of the entanglement in quantum gases.
Moreover, in Phys. Rev. A-1 (2016) we presented a general framework to describe the competition between global quantum measurement and standard local processes (tunneling and on-site interaction) in a strongly correlated many-body system. We demonstrated the following new phenomena: design of nonlocal spatially structured environment for otherwise closed many-body system, long-range correlated tunneling, nonlocal quantum Zeno effect, generation of multimode Schrödinger cat states, break-up and protection of strongly interacting fermion pairs.
In Atoms (2015) we have shown the measurement-induced entanglement between fermion spin components on a lattice, and showed that the homodyne detection can produce more robust states, than those produced by photon number measurements.
In Phys. Rev. A-3 (2016), we have extended the notion of quantum Zeno dynamics in the realm of non-Hermitian processes. Moreover, we presented an unconventional scenario for quantum Zeno dynamics: a system evolves within a Zeno subspace thanks to Raman-like transitions via virtual states outside that subspace. This corresponds to a rather strong, but not projective quantum measurement.
In Scientific Reports (2016), we demonstrated how the quantum backaction of weak continuous measurement can lead to the generation of antiferromagnetic order and density modulations in the system of ultracold fermions in optical lattices.
In Phys. Rev. A-4 (2016), we demonstrated that joining the ideas of quantum measurement and quantum optical lattices can broaden the field of quantum simulations, allowing simulating numerous models such as superexchange interactions, multispecies Dicke model, pair creation and annihilation, dynamical gauge fields, etc.
In arXiv:1601.02230 we demonstrated that the quantum feedback control can strongly influence the stability region of a BEC trapped inside a cavity. Moreover, it can be used to precisely position a BEC in space and tune the phase of the generated light.
In New J. Phys.-1 (2016), we predicted a nontrivial type of dynamics resulting from the novel competition between the quantum backaction of weak measurement and unitary many-body (or multimode) dynamics.
In Optica (OSA) (2016), we have described the quantum feedback control of novel many-body states, which appear as a result of the competition between the weak measurement backaction and many-body dynamics: multimode density waves and supersolids, antiferromagnetic and NOON states.
In Scientific Reports (2017), instead of coupling light to the atomic on-site density, we propose a method of coupling directly to the matter-phase-related variables. This constitutes a novel type of quantum measurements and projections, thus generalizing the standard measurement postulate for the case of competition between the weak measurement backaction and system's own dynamics.
- We developed a model to describe the ultracold atoms trapped in a fully quantum potential (“quantum optical lattices”), merging cavity QED and physics of ultracold gases. For example, the generalized Bose-Hubbard model taking into account the light quantization was formulated. (Eur. Phys. Journal D (2008), Phys. Rev. A (2007))
In a recent paper (Phys. Rev. Lett.-2), we demonstrated novel phase transitions solely due to the quantum light-matter correlations in a quantum optical lattice. Moreover, we showed the generation of nonclassical light (e.g. squeezed) in such systems (New J. Phys. (2015)).
In Phys. Rev. A-2 (2016), we proposed a new type of quantum simulators based on the collective enhancement of light-matter interactions.
In New J. Phys.-2 (2016), we showed that the emergent global bond order (i.e. the self-organization of matter-wave coherences, rather than densities) is linked to the valence bond solids (VBS). This opens a novel avenue for global quantum simulations, in particular, of high-Tc superconductors.
SELECTED PUBLICATIONS (cf. CV for the full list)
- "Probing quantum phases of ultracold atoms in optical lattices by transmission spectra in cavity QED", I.B. Mekhov, C. Maschler, H. Ritsch, quant-ph/0702125, Nature Phys. 3, 319 (2007);
- "Cavity-enhanced light scattering in optical lattices to probe atomic quantum statistics", I.B. Mekhov, C. Maschler, and H. Ritsch, Phys. Rev. Lett. 98, 100402 (2007);
- "Light scattering from ultracold atoms in optical lattices as an optical probe of quantum statistics", I.B. Mekhov, C. Maschler, and H. Ritsch, Phys. Rev. A 76, 053618 (2007);
- "Ultracold atoms in optical lattices generated by quantized light fields2, C. Maschler, I.B. Mekhov, and H. Ritsch, Eur. Phys. J. D 46, 545 (2008);
- "Quantum optics with quantum gases", I.B. Mekhov and H. Ritsch, arXiv:0901.3335, Laser Physics 19, 610 (2009);
- "QND measurements and state preparation in quantum gases by light detection", I.B. Mekhov and H. Ritsch, Phys. Rev. Lett. 102, 020403 (2009);
- "Quantum optics with quantum gases: controlled state reduction by designed light scattering," I.B. Mekhov and H. Ritsch, Phys. Rev. A 80, 013604 (2009);
- "Quantum optical measurements in ultracold gases: macroscopic Bose-Einstein condensates", I.B. Mekhov, H. Ritsch, arXiv:0911.0389, Laser Physics 20, 694 (2010);
- "Atom state evolution and collapse in ultracold gases during light scattering into a cavity", I.B. Mekhov and H. Ritsch, arXiv:1103.4411, Laser Physics 21, 1486 (2011).
- "Few-body bound states in dipolar gases and their detection," B. Wunsch, N. T. Zinner, I. B. Mekhov, S.-J. Huang, D.-W. Wang, and E. Demler, Phys. Rev. Lett. 107, 073201 (2011);
- "Few-body bound complexes in 1D dipolar gases and their non-destructive optical detection," N. T. Zinner, B. Wunsch, I. B. Mekhov, S.-J. Huang, D.-W. Wang, and E. Demler, Phys. Rev. A 84, 063606 (2011);
- "Quantum optics with ultracold quantum gases: towards the full quantum regime of the light–matter interaction," I.B. Mekhov and H. Ritsch, arXiv:1203.0552, Journ. Phys. B 45, 102001 (2012);
- "Quantum Non-Demolition Detection of Polar Molecule Complexes: Dimers, Trimers, Tetramers," I. B. Mekhov, Laser Physics 23, 015501 (2013).
- "Probing Matter-Field and Atom-Number Correlations in Optical Lattices by Global Nondestructive Addressing," W. Kozlowski, S. F. Caballero-Benitez, and I. B. Mekhov, Phys. Rev. A 92, 013613(2015).
- "Multipartite Entangled Spatial Modes of Ultracold Atoms Generated and Controlled by Quantum Measurement," T. J. Elliott, W. Kozlowski, S. F. Caballero-Benitez, and I. B. Mekhov, Phys. Rev. Lett. 114, 113604 (2015).
- "Probing and Manipulating Fermionic and Bosonic QuantumGases with Quantum Light," T. J. Elliott, G. Mazzucchi, W. Kozlowski, S. F. Caballero-Benitez and I. B. Mekhov, Atoms 3, 392 (2015), Invited paper in a Special Issue "Cavity QED with ultracold atoms".
- "Quantum optical lattices for emergent many-body phases of ultracold atoms," S. F. Caballero-Benitez and I. B. Mekhov, Phys. Rev. Lett. 115, 243604 (2015).
- "Quantum properties of light scattered from structured many-body phases of ultracold atoms in quantum optical lattices," S. F. Caballero-Benitez and I. B. Mekhov, New J. Phys. 17, 123023(2015).
- "Non-Hermitian Dynamics in the Quantum Zeno Limit," W. Kozlowski, S. F. Caballero-Benitez, and I. B. Mekhov, arXiv:1510.04857, Phys. Rev. A 94, 012123 (2016).
- "Quantum measurement-induced antiferromagnetic order and density modulations in ultracold Fermi gases in optical lattices," G. Mazzucchi, S. F. Caballero-Benitez, and I. B. Mekhov, arXiv:1510.04883, Scientific Reports 6, 31196 (2016).
- "Engineering Many-Body Dynamics with Quantum Light Potentials and Measurements," T. J. Elliott and I. B. Mekhov, arXiv:1511.00980, Phys. Rev. A 94, 013614 (2016).
- "Quantum Measurement-induced Dynamics of Many-Body Ultracold Bosonic and Fermionic Systems in Optical Lattices," G. Mazzucchi, W. Kozlowski, S. F. Caballero-Benitez, T. J. Elliott, and I. B. Mekhov, Phys. Rev. A 93, 023632 (2016).
- "Incoherent quantum feedback control of collective light scattering by Bose-Einstein condensates," D. A. Ivanov, T. Yu. Ivanova, and I. B. Mekhov, arXiv:1601.02230.
- "Quantum simulators based on the global collective light-matter interaction," S. F. Caballero-Benitez, G. Mazzucchi, and I. B. Mekhov, Phys. Rev. A 93, 063632 (2016).
- "Collective dynamics of multimode bosonic systems induced by weak quantum measurement," G. Mazzucchi, W. Kozlowski, S. F. Caballero-Benitez, and I. B. Mekhov, New J. Phys. 18, 073017 (2016).
- "Bond Order via Light-Induced Synthetic Many-body Interactions of Ultracold Atoms in Optical Lattices," S. F. Caballero-Benitez, and I. B. Mekhov, New J. Phys. 18, 113010 (2016).
- "Quantum optical feedback control for creating strong correlations in many-body systems," G. Mazzucchi, S. F. Caballero-Benitez, D. A. Ivanov, and I. B. Mekhov, Optica 3, 1213 (OSA) (2016).
- "Quantum State Reduction by Matter-Phase-Related Measurements in Optical Lattices," W. Kozlowski, S. F. Caballero-Benitez, and I. B. Mekhov, Scientific Reports 7, 42597 (2017).
- "Cavityless self-organization of ultracold atoms due to the feedback-induced phase transition," D. A. Ivanov, T. Yu. Ivanova, S. F. Caballero-Benitez, and I. B. Mekhov, arXiv:2003.00191 (2020).
- "Feedback-Induced Quantum Phase Transitions Using Weak Measurements," D. A. Ivanov, T. Yu. Ivanova, S. F. Caballero-Benitez, and I. B. Mekhov, Phys. Rev. Lett. 124, 010603 (2020).
Optically dense media, polaritons, strong light-matter coupling, superradiance
I am interested in the study of optically dense resonant media. Especially, in the regime of strong light-matter coupling both in a cavity and free space. Such phenomena can be understood in terms of polaritons and collective superradiance.
I am interested in the realizations in both atomic and solid-state (semiconductor nanostructures with quantum wells and quantum dots) media.
We have proposed a novel type of collective parametric processes, which cannot be explained by any single-atom model:
- We demonstrated the light amplification in the strong coupling regime in a cavity. (Quantum Information Processing (2006), Laser Physics (2005))
- Moreover, the parametric amplification of polaritons and solitons in free space without use of any cavity has been proved. (Phys. Rev. A (2004), Phys. Rev. A (2003), Laser Physics (2005), Quantum Information Processing (2006))
SELECTED PUBLICATIONS (cf. CV for the full list)
- "Strong light-matter coupling: coherent parametric interactions in a cavity and free-space", V.S. Egorov, V.N. Lebedev, I.B. Mekhov, P.V. Moroshkin, I.A. Chekhonin, and S.N. Bagayev, "Quantum Information Processing – From Theory to Experiment", v. 199, p. 341, IOS Press (Amsterdam, Netherlands, 2006);
- "Coherent light sources under strong field–matter coupling in an optically dense resonant medium without population inversion", S.N. Bagayev, V.V. Vasil’ev, V.S. Egorov, V.N. Lebedev, I. B. Mekhov, P. V. Moroshkin, A. N. Fedorov, and I. A. Chekhonin, Laser Physics, 15, 975 (2005);
- "Coherent interaction of laser pulses in a resonant optically dense extended medium under the regime of strong field-matter coupling", V.S. Egorov, V.N. Lebedev, I.B. Mekhov, P.V. Moroshkin, I.A. Chekhonin, and S.N. Bagayev, Phys. Rev. A 69, 033804 (2004);
- "Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms", S.N. Bagayev, V.S. Egorov, I.B. Mekhov, P.V. Moroshkin, I.A. Chekhonin, E.M. Davliatchine, and E. Kindel, Phys. Rev. A 68, 043812 (2003);
- "Nonstationary parametric amplification of polychromatic radiation propagating in an extended absorbing resonant medium", S.N. Bagaev, V.S. Egorov, I.B. Mekhov, P.V. Moroshkin, I.A. Chekhonin, E. M. Davliatchine, and E. Kindel, Opt. Spectrosc. 94, 92 (2003);
- "Parametric collective phenomena during the propagation of polychromatic laser pulses in an optically dense resonant medium without population inversion", S.N. Bagaev, V.S. Egorov, I.B. Mekhov, P.V. Moroshkin, I.A. Chekhonin, Opt. Spectrosc. 93, 955 (2002);
Other interests
I have also studied different aspects of nonlinear dynamics and statistical physics:
- solitons,
- parametric interactions,
- light squeezing,
- semiconductor lasers with quantum wells (VCSELs),
- plasma physics (kinetics of particles at ultralow (Phys. Rev. E (1999)) and extremely high (ISPC-14 (1999), Hakone VII (2000)) pressures).
Quantum optics of ultracold quantum gases:
Studying the ultimate quantum level of the light-matter interaction
My Theory Group members within the period 2011 - 2016:
Post-doc: Santiago Caballero Benitez
PhD students: Wojciech Kozlowski, Gabriel Mazzucchi, Thomas Elliott, Felix Tennie (See the GROUP PHOTO.)
RESEARCH DESCRIPTION
Theoretical quantum optics of ultracold quantum gases
Studying the ultimate quantum limit of the light-matter interaction
A REVIEW PAPER is available at Journ. Phys. B 45, 102001 (2012) (arXiv:1203.0552)
Both quantum optics and many-body physics of the lowest achievable temperatures are very active fields of modern research. However, the interaction between them is far from being complete.
In the most theoretical and experimental works on ultracold atoms, the role of light is reduced to a classical tool for preparing intriguing atomic states. In contrast, the main goal of this research is to develop a theory of the phenomena, where the quantum natures of both ultracold matter and light play equally important roles.
This research will close the gap between quantum optics and physics of ultracold quantum matter, considering the ultimate quantum regime of the light-matter interaction. The experiments on this regime became possible just several years ago, which makes the interaction between the theory and experiment promising.
First, the quantized light serves as a quantum nondemolition (QND) probe sensitive to the quantum states of ultracold particles. The applications exist for ultracold atomic gases (Nature Physics (2007), Phys. Rev. Lett. (2007), Phys. Rev. A (2007), Laser Physics (2009)), polar molecules (Phys. Rev. Lett. (2011), Phys. Rev. A (2011), Laser Physics (2013)) and other systems as well.
In a recent paper (Phys. Rev. A (2015)), we proved that light is not only sensitive to the density correlations, but also reflects the matter-field interference at its shortest possible distance in an optical lattice. We also showed, how to distinguish the Bose Glass, Mott insulator and superfluid phases.
Second, due to the light-matter entanglement, the quantum measurement-based preparation of many-body atomic states is possible. The class of emerging atomic states can be chosen via optical geometry, thus, the light scattering constitutes a quantum measurement with a controllable form of the measurement back-action. For example, the atom number squeezed and Schrödinger cat states can be prepared. (Phys. Rev. Lett. (2009), Phys. Rev. A (2009), Laser Physics (2010), Laser Phys. (2011))
In a recent paper (Phys. Rev. Lett.-1 (2015)), we have shown, how to generate multiple spatial modes of matter fields using the quantum measurement. The modes have nontrivial spatial overlap, display genuine multipartite entanglement, and can be used for measurement and detection of the entanglement in quantum gases.
Moreover, in Phys. Rev. A-1 (2016) we presented a general framework to describe the competition between global quantum measurement and standard local processes (tunneling and on-site interaction) in a strongly correlated many-body system. We demonstrated the following new phenomena: design of nonlocal spatially structured environment for otherwise closed many-body system, long-range correlated tunneling, nonlocal quantum Zeno effect, generation of multimode Schrödinger cat states, break-up and protection of strongly interacting fermion pairs.
In Atoms (2015) we have shown the measurement-induced entanglement between fermion spin components on a lattice, and showed that the homodyne detection can produce more robust states, than those produced by photon number measurements.
In Phys. Rev. A-3 (2016), we have extended the notion of quantum Zeno dynamics in the realm of non-Hermitian processes. Moreover, we presented an unconventional scenario for quantum Zeno dynamics: a system evolves within a Zeno subspace thanks to Raman-like transitions via virtual states outside that subspace. This corresponds to a rather strong, but not projective quantum measurement.
In Scientific Reports (2016), we demonstrated how the quantum backaction of weak continuous measurement can lead to the generation of antiferromagnetic order and density modulations in the system of ultracold fermions in optical lattices.
In Phys. Rev. A-4 (2016), we demonstrated that joining the ideas of quantum measurement and quantum optical lattices can broaden the field of quantum simulations, allowing simulating numerous models such as superexchange interactions, multispecies Dicke model, pair creation and annihilation, dynamical gauge fields, etc.
In arXiv:1601.02230 we demonstrated that the quantum feedback control can strongly influence the stability region of a BEC trapped inside a cavity. Moreover, it can be used to precisely position a BEC in space and tune the phase of the generated light.
In New J. Phys.-1 (2016), we predicted a nontrivial type of dynamics resulting from the novel competition between the quantum backaction of weak measurement and unitary many-body (or multimode) dynamics.
In Optica (OSA) (2016), we have described the quantum feedback control of novel many-body states, which appear as a result of the competition between the weak measurement backaction and many-body dynamics: multimode density waves and supersolids, antiferromagnetic and NOON states.
In Scientific Reports (2017), instead of coupling light to the atomic on-site density, we propose a method of coupling directly to the matter-phase-related variables. This constitutes a novel type of quantum measurements and projections, thus generalizing the standard measurement postulate for the case of competition between the weak measurement backaction and system's own dynamics.
Third, trapping atoms inside an optical cavity one creates the light potential, which is a quantized and dynamical variable itself, rather a prescribed classical function as it is usual in the quantum gas problems. In the cavity QED with quantum gases, the self-consistent solution for light and particles is required, which enriches the picture of quantum many-body states of atoms trapped in quantum potentials. (Eur. Phys. Journal D (2008), Phys. Rev. A (2007))
In a recent paper (Phys. Rev. Lett.-2 (2015)), we demonstrated novel phase transitions solely due to the quantum light-matter correlations in a quantum optical lattice.
Moreover, we showed the generation of nonclassical light (e.g. squeezed) in such systems (New J. Phys. (2015)).
In Phys. Rev. A-2 (2016), we proposed a new type of quantum simulators based on the collective enhancement of light-matter interactions.
In New J. Phys.-2 (2016), we showed that the emergent global bond order (i.e. the self-organization of matter-wave coherences, rather than densities) is linked to the valence bond solids (VBS). This opens a novel avenue for global quantum simulations, in particular, of high-Tc superconductors.
The application of those fully quantum models to the systems of semiconductor nanophotonics are of interest as well.
NEWS
- Visit by Professor Peter Domokos (Wigner Research Centre for Physics, Budapest)
- Visit by Dr. Denis Ivanov (St. Petersburg State University)
- Visit by Professor Janne Ruostekoski (University of Southampton)
- Visit by Professor Michael Hartmann (Heriot-Watt University, Edinburgh)
- Visit by Professor Jacob Sherson (Aarhus University)
- Welcome to Santiago Caballero Benitez, who has started his postdoc!
- Visit by Professor Guangjiong Dong (East China Normal University, Shanghai)
- Welcome to a new graduate student Thomas Elliott!
- Visit by Professor Claus Zimmermann (University of Tübingen)
- A REVIEW paper is available at Journ. Phys. B 45, 102001 (2012) (arXiv:1203.0552)
- Visit by Dr. Vincent Boyer (University of Birmingham)
- Wojciech Kozlowski, Gabriel Mazzucchi and Felix Tennie have joined the group as graduate students.
RECENT RESULTS:
- We developed a concept of "quantum optical lattices," where the quantized light creates fully quantum and dynamical trapping potential for ultracold bosons and fermions.
- We have introduced the quantum measurement into a many-body system. We have shown that the quantum backaction of weak (non-projective) measurement can effeciently compete with unitary dynamics, thus, constituting a novel source of the competitions in many-body systems. This leads to a plethora of novel effects such as the giant oscillations at single quantum trajectories, long-range correlated pair tunneling, Raman-like virtual transitions in quantum Zeno subspaces, measurement-induced protection and break-up of fermion pairs, and measurement-induced antiferromagnetic orders.
- We have suggested quantum simulations based on the collective enhancement of light-matter interaction. We demonstrated the emergence of not only density orders (e.g., density waves and supersolids), but also the orders of matter-wave coherences (bond orders). This is well beyond predictions of standard Dicke and Bose-Hubbard models.
RESEARCH HIGHLIGHTS
Phys. Rev. A (2015):
The light is not only sensitive to the density correlations, but also reflects the matter-field interference at its shortest possible distance in an optical lattice.
Light scattering distinguishes all quantum phases in the Bose Glass - Mott insulator - superfluid phase transition.
Phys. Rev. Lett.-1 (2015):
We have shown, how to generate multiple spatial modes of matter fields using the quantum measurement. The modes have nontrivial spatial overlap, display genuine multipartite entanglement, and can be used for measurement and detection of the entanglement in quantum gases. We demonstrate non-Gaussian generalizations of multimode squeezed, parametric down-conversion, and Dicke states.
Phys. Rev. Lett.-2 (2015):
We demonstrated novel phase transitions solely due to the quantum light-matter correlations in a quantum optical lattice. The competition between light-field and matter-field coherences leads to novel phases (e.g. delocalized dimers), beyond density-induced orders such as multimode generalizations of density waves and supersolid states.
New J. Phys. (2015):
We demonstrated that light scattered from novel phases of atoms in quantum optical lattices has essentially nonclassical properties (e.g. squeezing).
Atoms (2015), Special Issue:
We considered quantum nondemolition measurement of many-body states of strongly interacting and non-interacting fermions in optical lattices, and demonstrated the measurement-induced entanglement of spin components and generation of macroscopic superposition states on a lattice. We showed that the quadrature measurements can produce Schrödinger cat states, which are more robust with respect to photon losses, than those obtained by the photon number detection. We also showed that quantum optical lattices generated in a cavity change quantum phases of ultracold bosons.
Phys. Rev. A-1 (2016):
We presented a general framework to describe the competition between global quantum measurement and standard local processes (tunneling and on-site interaction) in a strongly correlated many-body system. We demonstrated the following new phenomena: design of nonlocal spatially structured environment for otherwise closed many-body system, long-range correlated tunneling, nonlocal quantum Zeno effect, generation of multimode Schrödinger cat states, break-up and protection of strongly interacting fermion pairs.
Phys. Rev. A-2 (2016):
We suggested a novel type of quantum simulators based on the collective enhancement of light-matter interactions.
New J. Phys.-1 (2016):
We predicted a nontrivial type of dynamics resulting from the novel competition between the quantum backaction of weak measurement and unitary many-body (or multimode) dynamics.
Phys. Rev. A-3 (2016):
We have extended the notion of quantum Zeno dynamics in the realm of non-Hermitian processes. Moreover, we presented an unconventional scenario for quantum Zeno dynamics: a system evolves within a Zeno subspace thanks to Raman-like transitions via virtual states outside that subspace. This corresponds to a rather strong, but not projective quantum measurement.
Scientific Reports (2016):
We demonstrated how the quantum backaction of weak continuous measurement can lead to the generation of antiferromagnetic order and density modulations in the system of ultracold fermions in optical lattices.
Phys. Rev. A-4 (2016):
We demonstrated that joining the ideas of quantum measurement and quantum optical lattices can broaden the field of quantum simulations, allowing simulating numerous models such as superexchange interactions, multispecies Dicke model, pair creation and annihilation, dynamical gauge fields, etc.
arXiv:1601.02230:
We demonstrated that the quantum feedback control can strongly influence the stability region of a BEC trapped inside a cavity. Moreover, it can be used to precisely position a BEC in space and tune the phase of the generated light.
New J. Phys.-2 (2016):
We showed that the emergent global bond order (i.e. the self-organization of matter-wave coherences, rather than densities) is linked to the valence bond solids (VBS). This opens a novel avenue for global quantum simulations, in particular, of high-Tc superconductors.
Optica (OSA) (2016):
We have described the quantum feedback control of novel many-body states, which appear as a result of the competition between the weak measurement backaction and many-body dynamics: multimode density waves and supersolids, antiferromagnetic and NOON states.
Scientific Reports (2017):
Instead of coupling light to the atomic on-site density, we propose a method of coupling directly to the matter-phase-related variables. This constitutes a novel type of quantum measurements and projections, thus generalizing the standard measurement postulate for the case of competition between the weak measurement backaction and system's own dynamics.
RECENT PAPERS:
Phys. Rev. Lett.-1 (2015), Phys. Rev. Lett.-2 (2015), New J. Phys. (2015), Phys. Rev. A (2015), Atoms (2015), Scientific Reports (2016), New J. Phys.-1 (2016), Phys. Rev. A-1 (2016), Phys. Rev. A-2 (2016), Phys. Rev. A-3 (2016), Phys. Rev. A-4 (2016), arXiv:1601.02230, New J. Phys.-2 (2016), Optica (OSA) (2016), Scientific Reports (2017).
A REVIEW PAPER is available at Journ. Phys. B 45, 102001 (2012) (arXiv:1203.0552)
PhD THESES:
W. Kozlowski. Competition between Weak Quantum Measurement and Many-Body Dynamics in Ultracold Bosonic Gases. PhD Thesis, Oxford (2017). ORA link 1. ORA link 2.
G. Mazzucchi. Conditional Many-Body Dynamics and Quantum Control of Ultracold Fermions and Bosons in Optical Lattices Coupled to Quantized Light. PhD Thesis, Oxford (2017). ORA link 1. ORA link 2.
Quantum Ideas (Keble College)
Quantum Information (Department of Physics)
Quantum Optics (Department of Physics)
Quantum Engineering (University Paris-Saclay)