Theory of Cold Atoms @ Seoul National University

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Beneficial and detrimental entanglement for quantum battery charging

AVS Quantum Sci. 6, 012001 (2024).

AVS Quantum Sci. 6, 012001 (2024).

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

Phys. Rev. D 107, L121502 (Letter) (2023).

Phys. Rev. D 107, L121502 (Letter) (2023).

Number-conserving solution for dynamical quantum backreaction in a Bose-Einstein condensate

Phys. Rev. A 106, 053319 (2022).

Phys. Rev. A 106, 053319 (2022).

Implementation-independent sufficient condition of the Knill-Laflamme type for the autonomous protection of logical qudits by strong engineered dissipation

Phys. Rev. A 98, 012317 (2018).

Phys. Rev. A 98, 012317 (2018).

Probing the Scale Invariance of the Inflationary Power Spectrum in Expanding Quasi-Two-Dimensional Dipolar Condensates

Phys. Rev. Lett. 118, 130404 (2017).

Phys. Rev. Lett. 118, 130404 (2017).

Revealing Single-Trap Condensate Fragmentation by Measuring Density-Density Correlations after Time of Flight

Phys. Rev. Lett. 113, 140404 (2014).

Phys. Rev. Lett. 113, 140404 (2014).

Ultrafast quantum random access memory utilizing single Rydberg atoms in a Bose-Einstein condensate

Phys. Rev. Lett. 111, 240504 (2013).

Phys. Rev. Lett. 111, 240504 (2013).

Fragmented many-body ground states for scalar bosons in a single trap

Phys. Rev. Lett. 103, 060402 (2009).

Phys. Rev. Lett. 103, 060402 (2009).

Vortex quantum creation and winding number scaling in a quenched spinor Bose gas

Phys. Rev. Lett. 99, 120407 (2007).

Phys. Rev. Lett. 99, 120407 (2007).

Sweeping from the superfluid to the Mott phase in the Bose-Hubbard model

Phys. Rev. Lett. 97, 200601 (2006).

Phys. Rev. Lett. 97, 200601 (2006).

Mean-field expansion in Bose-Einstein condensates with finite-range interactions

Int. J. Mod. Phys. B 20, 3555-3565 (2006).

Int. J. Mod. Phys. B 20, 3555-3565 (2006).

Stability of quasi-two-dimensional Bose-Einstein condensates with dominant dipole-dipole interactions

Phys. Rev. A 73, 031602 (Rapid Communication) (2006).

Phys. Rev. A 73, 031602 (Rapid Communication) (2006).

Quantum simulation of cosmic inflation in two-component Bose-Einstein condensates

Phys. Rev. A 70, 063615 (2004).

Phys. Rev. A 70, 063615 (2004).

"Cosmological" quasiparticle production in harmonically trapped superfluid gases

Phys. Rev. A 69, 033602 (2004).

Phys. Rev. A 69, 033602 (2004).

Gibbons-Hawking Effect in the Sonic de Sitter Space-Time of an Expanding Bose-Einstein-Condensed Gas

Phys. Rev. Lett. 91, 240407 (2003).

Phys. Rev. Lett. 91, 240407 (2003).

Vortex states of rapidly rotating dilute Bose-Einstein condensates

Phys. Rev. Lett. 90, 140402 (2003).

Phys. Rev. Lett. 90, 140402 (2003).

강명균 (Myung-Kyun Kang)

Measurement Theory of Quantum Many-Body States

BK Thesis Excellence Award 2016

Measurement Theory of Quantum Many-Body States

BK Thesis Excellence Award 2016

A variety of cosmologically motivated effective quasiparticle space-times can be produced in harmonically trapped superfluid Bose and Fermi gases. We have studied the analog of cosmological particle production in these effective space-times, induced by trapping potentials and coupling constants possessing an arbitrary time dependence. The WKB probabilities for phonon creation from the superfluid vacuum have been calculated, and an experimental procedure to detect quasiparticle production by measuring density-density correlation functions was proposed.

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates,
Phys. Rev. D
107, L121502 (Letter)
(2023).

,
Probing the Scale Invariance of the Inflationary Power Spectrum in Expanding Quasi-Two-Dimensional Dipolar Condensates,
Phys. Rev. Lett.
118, 130404
(2017).

(See also Science Dong-a (과학동아) Article 기체 방울 속에 우주와 블랙홀을 재현하다. )

,
(See also Science Dong-a (과학동아) Article 기체 방울 속에 우주와 블랙홀을 재현하다. )

Quantum simulation of cosmic inflation in two-component Bose-Einstein condensates,
Phys. Rev. A
70, 063615
(2004).

,
“Cosmological” quasiparticle production in harmonically trapped superfluid gases,
Phys. Rev. A
69, 033602
(2004).

,
Gibbons-Hawking Effect in the Sonic de Sitter Space-Time of an Expanding Bose-Einstein-Condensed Gas,
Phys. Rev. Lett.
91, 240407
(2003).

,
Quantum metrology aims to describe the potentially enhanced usefulness of quantum systems over classical systems to carry out precise measurements of important physical quantities. To this end, the quantum Cramér-Rao theorem along with the Quantum Fisher Information contained in it gives an ultimate bound on the precision of the estimation of any classical parameter.
In a quantum estimation framework, many-body physics can play a very valuable role. Indeed, many-body correlations are a useful resource for quantum metrology. Using our expertise on many-body physics, and on dilute ultracold gases in particular, we aim to better understand the role of interactions in metrology.

Classical and quantum metrology of the Lieb-Liniger model,
Phys. Rev. A
106, 062442
(2022).

,
Intrinsic measurement errors for the speed of light in vacuum,
Class. Quantum Grav.
34, 175009
(2017).

,
Amplification of the quantum superposition macroscopicity of a flux qubit by a magnetized Bose gas,
Phys. Rev. A
94, 042320
(2016).

,
We have derived an upper bound for the charging power of quantum batteries, by isolating, in the maximum charging power, the quantum speed limit from the charging operator and the energy gap of the battery cells, from a characteristic *quantum advantage* quantity $\Gamma_C(\hat \rho)$, where $\hat \rho$ is the density matrix of the quantum state.
Importantly, $\Gamma_C(\hat \rho)$ encapsulates the answer to the question whether a quantum advantage solely in terms of the hallmark of quantum mechanics, that is entanglement, can be identified, to be able to classify the batteries as genuinely "quantum."

We have established a long-lived and rapidly accessible quantum memory unit (quantum RAM) in a hybrid system. The operational Hilbert space is spanned by states involving the two macroscopically occupied hyperfine levels of a miscible binary atomic Bose-Einstein condensate and the Rydberg state of a single atom therein, which interacts magnetically with the flux qubit of a SQUID. An arbitrary qubit state, initially prepared using the flux qubit, can be rapidly transferred to and from the trapped atomic ensemble in approximately 10 ns and with a large fidelity of 97%, via an effective two-photon process using an external laser for the transition to the Rydberg level.

We have established a long-lived and rapidly accessible quantum memory unit (quantum RAM) in a hybrid system. The operational Hilbert space is spanned by states involving the two macroscopically occupied hyperfine levels of a miscible binary atomic Bose-Einstein condensate and the Rydberg state of a single atom therein, which interacts magnetically with the flux qubit of a SQUID. An arbitrary qubit state, initially prepared using the flux qubit, can be rapidly transferred to and from the trapped atomic ensemble in approximately 10 ns and with a large fidelity of 97%, via an effective two-photon process using an external laser for the transition to the Rydberg level.

Beneficial and detrimental entanglement for quantum battery charging,
AVS Quantum Sci.
6, 012001
(2024).

,
Ultrafast Quantum Random Access Memory Utilizing Single Rydberg Atoms in a Bose-Einstein Condensate,
Phys. Rev. Lett.
111, 024504
(2013).

,
Hybrid of superconducting quantum interference device and atomic Bose-Einstein condensate: An architecture for quantum information processing,
Phys. Rev. A
87, 052303
(2013).

,
,
We investigate whether the many-body ground states of bosons in a generalized two-mode model with localized inhomogeneous single-particle orbitals and anisotropic long-range interactions (e.g., dipole-dipole interactions) are coherent or fragmented. It is demonstrated that fragmentation can take place in a single trap for positive values of the interaction couplings, implying that the system is potentially stable. Furthermore, the degree of fragmentation is shown to be insensitive to small perturbations on the single-particle level.

"Photonic" Cat States from Strongly Interacting Matter Waves,
Phys. Rev. Lett.
115, 260404
(2015).

,
Revealing Single-Trap Condensate Fragmentation by Measuring Density-Density Correlations after Time of Flight,
Phys. Rev. Lett.
113, 140404
(2014).

,
Robustness of fragmented condensate many-body states for continuous distribution amplitudes in Fock space,
Phys. Rev. A
88, 053602
(2013).

,
Fragmented Many-Body Ground States for Scalar Bosons in a Single Trap,
Phys. Rev. Lett.
103, 060402
(2009).

,
Beneficial and detrimental entanglement for quantum battery charging

AVS Quantum Sci. 6, 012001 (2024).

AVS Quantum Sci. 6, 012001 (2024).

Impact of trans-Planckian excitations on black-hole radiation in dipolar condensates

Phys. Rev. D 107, L121502 (Letter) (2023).

Phys. Rev. D 107, L121502 (Letter) (2023).

Dispersive censor of acoustic spacetimes with a shock-wave singularity

Phys. Rev. D 107, 084023 (2023).

Phys. Rev. D 107, 084023 (2023).

Nonlocal field theory of quasiparticle scattering in dipolar Bose-Einstein condensates

SciPost Phys. Core 6, 003 (2023).

SciPost Phys. Core 6, 003 (2023).

Number-conserving solution for dynamical quantum backreaction in a Bose-Einstein condensate

Phys. Rev. A 106, 053319 (2022).

Phys. Rev. A 106, 053319 (2022).

Existence of steady-state black hole analogs in finite quasi-one-dimensional Bose-Einstein condensates

Phys. Rev. D 105, 124066 (2022).

Phys. Rev. D 105, 124066 (2022).

Testing the upper bound on the speed of scrambling with an analogue of Hawking radiation using trapped ions

Eur. Phys. J. C 82, 212 (2022).

Eur. Phys. J. C 82, 212 (2022).

Inherent nonlinearity of fluid motion and acoustic gravitational wave memory

Phys. Rev. D 105, 022003 (2022).

Phys. Rev. D 105, 022003 (2022).

Benchmarking the multiconfigurational Hartree method by the exact wavefunction of two harmonically trapped bosons with contact interaction

Ann. Phys. (N. Y.) 434, 168592 (2021).

Ann. Phys. (N. Y.) 434, 168592 (2021).

Stoner-Wohlfarth switching of the condensate magnetization in a dipolar spinor gas and the metrology of excitation damping

Phys. Rev. A 102, 013315 (2020).

Phys. Rev. A 102, 013315 (2020).

Self-consistent determination of the many-body state of ultracold bosonic atoms in a one-dimensional harmonic trap

Ann. Phys. (N. Y.) 405, 274 (2019).

Ann. Phys. (N. Y.) 405, 274 (2019).

Many-body quantum metrology with scalar bosons in a single potential well

Phys. Rev. A 99, 043618 (2019).

Phys. Rev. A 99, 043618 (2019).

Mesoscopics of half-quantum vortex pair deconfinement in a trapped spin-one condensate

Phys. Rev. A 98, 053602 (2018).

Phys. Rev. A 98, 053602 (2018).

Implementation-independent sufficient condition of the Knill-Laflamme type for the autonomous protection of logical qudits by strong engineered dissipation

Phys. Rev. A 98, 012317 (2018).

Phys. Rev. A 98, 012317 (2018).

Intrinsic measurement errors for the speed of light in vacuum

Class. Quantum Grav. 34, 175009 (2017).

Class. Quantum Grav. 34, 175009 (2017).

Probing the Scale Invariance of the Inflationary Power Spectrum in Expanding Quasi-Two-Dimensional Dipolar Condensates

Phys. Rev. Lett. 118, 130404 (2017).

Phys. Rev. Lett. 118, 130404 (2017).

Amplification of the quantum superposition macroscopicity of a flux qubit by a magnetized Bose gas

Phys. Rev. A 94, 042320 (2016).

Phys. Rev. A 94, 042320 (2016).

Quantum sine-Gordon dynamics on analogue curved spacetime in a weakly imperfect scalar Bose gas

Phys. Rev. D 94, 024051 (2016).

Phys. Rev. D 94, 024051 (2016).

Condensate fragmentation as a sensitive measure of the quantum many-body behavior of bosons with long-range interactions

Phys. Rev. A 91, 063621 (2015).

Phys. Rev. A 91, 063621 (2015).

Consistent perturbative treatment of the subohmic spin-boson model yielding arbitrarily small \(T_2/T_1\) decoherence time ratios

Phys. Rev. B 90, 220302 (Rapid Communication) (2014).

Phys. Rev. B 90, 220302 (Rapid Communication) (2014).

Revealing Single-Trap Condensate Fragmentation by Measuring Density-Density Correlations after Time of Flight

Phys. Rev. Lett. 113, 140404 (2014).

Phys. Rev. Lett. 113, 140404 (2014).

Universality of the Berezinskii–Kosterlitz–Thouless type of phase transition in the dipolar XY-model

New J. Phys. 16, 053011 (2014).

New J. Phys. 16, 053011 (2014).

Truncated many-body dynamics of interacting bosons: A variational principle with error monitoring

Int. J. Mod. Phys. B 28, 1550021 (2014).

Int. J. Mod. Phys. B 28, 1550021 (2014).

Ultrafast quantum random access memory utilizing single Rydberg atoms in a Bose-Einstein condensate

Phys. Rev. Lett. 111, 024504 (2013).

Phys. Rev. Lett. 111, 024504 (2013).

Robustness of fragmented condensate many-body states for continuous distribution amplitudes in Fock space

Phys. Rev. A 88, 053602 (2013).

Phys. Rev. A 88, 053602 (2013).

Interaction-induced coherence among polar bosons stored in triple-well potentials

Phys. Rev. A 88, 063608 (2013).

Phys. Rev. A 88, 063608 (2013).

Stability of spherically trapped three-dimensional Bose-Einstein condensates against macroscopic fragmentation

Phys. Rev. A 87, 023632 (2013).

Phys. Rev. A 87, 023632 (2013).

Hybrid of superconducting quantum interference device and atomic Bose-Einstein condensate: An architecture for quantum information processing

Phys. Rev. A 87, 052303 (2013).

Phys. Rev. A 87, 052303 (2013).

Verifying the observer dependence of quasiparticle counts in the analogue gravity of dilute ultracold quantum gases

arXiv:1205.5548 [cond-mat.quant-gas] (2012).

arXiv:1205.5548 [cond-mat.quant-gas] (2012).

Identifying strongly correlated supersolid states on the optical lattice by quench-induced $\pi$-states

EPL 99, 66003 (2012).

EPL 99, 66003 (2012).

Many-site coherence revivals in the extended Bose-Hubbard model and the Gutzwiller approximation

Phys. Rev. A 84, 063635 (2011).

Phys. Rev. A 84, 063635 (2011).

Emergence of a new pair-coherent phase in many-body quenches of repulsive bosons

Phys. Rev. A 84, 011604 (Rapid Communication) (2011).

Phys. Rev. A 84, 011604 (Rapid Communication) (2011).

System size scaling of topological defect creation in a second-order dynamical quantum phase transition

New J. Phys. 12, 095020 (2010).

New J. Phys. 12, 095020 (2010).

Interacting trapped bosons yield fragmented condensate states in low dimensions

Phys. Rev. A 82, 013607 (2010).

Phys. Rev. A 82, 013607 (2010).

Increased Cation Conductance in Human Erythrocytes Artificially Aged by Glycation

J. Membrane Biol. 235, 177-189 (2010).

J. Membrane Biol. 235, 177-189 (2010).

$O(N)$ symmetry-breaking quantum quench: Topological defects versus quasiparticles

Phys. Rev. D 81, 025017 (2010).

Phys. Rev. D 81, 025017 (2010).

Fragmented many-body ground states for scalar bosons in a single trap

Phys. Rev. Lett. 103, 060402 (2009).

Phys. Rev. Lett. 103, 060402 (2009).

Tunneling-induced damping of phase coherence revivals in deep optical lattices

Phys. Rev. A 78, 061603 (Rapid Communication) (2008).

Phys. Rev. A 78, 061603 (Rapid Communication) (2008).

Effect of fluctuations on the superfluid-supersolid phase transition on the lattice

Phys. Rev. A 78, 033604 (2008).

Phys. Rev. A 78, 033604 (2008).

Bogoliubov theory of quantum correlations in the time-dependent Bose-Hubbard model

Phys. Rev. A 77, 043615 (2008).

Phys. Rev. A 77, 043615 (2008).

Coherent single atom shuttle between two Bose-Einstein condensates

Phys. Rev. A 77, 031602 (Rapid Communication) (2008).

Phys. Rev. A 77, 031602 (Rapid Communication) (2008).

Vortex quantum creation and winding number scaling in a quenched spinor Bose gas

Phys. Rev. Lett. 99, 120407 (2007).

Phys. Rev. Lett. 99, 120407 (2007).

Dynamical Aspects of Analogue Gravity: The Backreaction of Quantum Fluctuations in Dilute Bose-Einstein Condensates

Lect. Notes Phys. 718, 93-113 (2007).

Lect. Notes Phys. 718, 93-113 (2007).

Sweeping from the superfluid to the Mott phase in the Bose-Hubbard model

Phys. Rev. Lett. 97, 200601 (2006).

Phys. Rev. Lett. 97, 200601 (2006).

Mean-field expansion in Bose-Einstein condensates with finite-range interactions

Int. J. Mod. Phys. B 20, 3555-3565 (2006).

Int. J. Mod. Phys. B 20, 3555-3565 (2006).

Stability of quasi-two-dimensional Bose-Einstein condensates with dominant dipole-dipole interactions

Phys. Rev. A 73, 031602 (Rapid Communication) (2006).

Phys. Rev. A 73, 031602 (Rapid Communication) (2006).

Reply to Comment on "Dynamical role of anyonic excitation statistics in rapidly rotating Bose gases"

Phys. Rev. Lett. 94, 208904 (2005).

Phys. Rev. Lett. 94, 208904 (2005).

Maximal length of trappped one-dimensional Bose-Einstein condensates

J. Low Temp. Phys. 138, 723-728 (2005).

J. Low Temp. Phys. 138, 723-728 (2005).

Quantum simulation of cosmic inflation in two-component Bose-Einstein condensates

Phys. Rev. A 70, 063615 (2004).

Phys. Rev. A 70, 063615 (2004).

Dynamical role of anyonic excitation statistics in rapidly rotating Bose gases

Phys. Rev. Lett. 93, 160403 (2004).

Phys. Rev. Lett. 93, 160403 (2004).

"Cosmological" quasiparticle production in harmonically trapped superfluid gases

Phys. Rev. A 69, 033602 (2004).

Phys. Rev. A 69, 033602 (2004).

Observer dependence for the phonon content of the sound field living on the effective curved space-time background of a Bose-Einstein condensate

Phys. Rev. D 69, 064021 (2004).

Phys. Rev. D 69, 064021 (2004).

Vortex liquids and vortex quantum Hall states in trapped rotating Bose gases

J. Phys. B: At. Mol. Opt. Phys. 37, S301-S310 (2004).

J. Phys. B: At. Mol. Opt. Phys. 37, S301-S310 (2004).

Zero-temperature damping of Bose-Einstein condensate oscillations by vortex-antivortex pair creation

Phys. Rev. A 68, 011602 (Rapid Communication) (2003).

Phys. Rev. A 68, 011602 (Rapid Communication) (2003).

Gibbons-Hawking Effect in the Sonic de Sitter Space-Time of an Expanding Bose-Einstein-Condensed Gas

Phys. Rev. Lett. 91, 240407 (2003).

Phys. Rev. Lett. 91, 240407 (2003).

Warped space-time for phonons moving in a perfect nonrelativistic fluid

Europhys. Lett. 62, 1-7 (2003).

Europhys. Lett. 62, 1-7 (2003).

On the space-time curvature experienced by quasiparticle excitations in the Painlevé-Gullstrand effective geometry

Ann. Phys. (N.Y.) 304, 22-39 (2003).

Ann. Phys. (N.Y.) 304, 22-39 (2003).

Vortex states of rapidly rotating dilute Bose-Einstein condensates

Phys. Rev. Lett. 90, 140402 (2003).

Phys. Rev. Lett. 90, 140402 (2003).

Electromagnetomotive force fields in noninertial reference frames and accelerated superconducting quantum interferometers

Phys. Rev. B 64, 214509 (2001).

Phys. Rev. B 64, 214509 (2001).

Specific heat of the Kelvin modes in low temperature superfluid turbulence

Phys. Rev. B 63, 212504 (2001).

Phys. Rev. B 63, 212504 (2001).

Thermal quasi-equilibrium states across Landau horizons in the effective gravity of superfluids

Int. J. Mod. Phys. D 10, 57-88 (2001).

Int. J. Mod. Phys. D 10, 57-88 (2001).

Tunnelling of topological line defects in strongly coupled superfluids

Ann. Phys. (Leipzig) 9, 523-570 (2000).

Ann. Phys. (Leipzig) 9, 523-570 (2000).

On the theory of vortex quantum tunnelling in the dense Bose superfluid helium II

Physica B 255, 41-54 (1998).

Physica B 255, 41-54 (1998).

Massive Charged Strings in the Description of Vortex Ring Quantum Nucleation

J. Low Temp. Phys. 110, 39-44 (1998).

J. Low Temp. Phys. 110, 39-44 (1998).

Transition probabilities for a Rydberg atom in the field of a gravitational wave

Class. Quantum Grav. 11, 463-474 (1994).

Class. Quantum Grav. 11, 463-474 (1994).

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