Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2504.14505 · Physical Review A

Quantum tomography of the superfluid-insulator transition for a mesoscopic atomtronic ring

Yehoshua Winsten, Doron Cohen

Published Jun 26, 2025• 2 citations
arXivHTMLPDF

Abstract

We provide a phase-space perspective for the analysis of the superfluid-insulator transition for finite-size Bose-Hubbard circuits. We explore how the eigenstates parametrically evolve as the inter-particle interaction is varied, paying attention to the fingerprints of chaos at the quantum phase-transition. Consequently, we demonstrate that the tomographic spectrum reflects the existence of mixed-regions of chaos and quasi-regular motion in phase-space. This tomographic semiclassical approach is much more efficient and informative compared to the traditional "level statistics" inspection. Of particular interest is the characterization of the fluctuations that are exhibited by the many-body eigenstates. In this context, we associate with each eigenstate a Higgs measure for the identification of amplitude modes of the order-parameter. Finally we focus on the formation of the lowest Goldstone and Higgs bands.

DOI
10.1103/tq97-7mjp

Related papers

Metastability, chaos and spectrum tomography for Bose-Hubbard rings and chains

Rajat, Doron Cohen

We analyze the metastability of Bose-Hubbard condensates for finite-size one-dimensional ring lattices and open chains, using a semiclassical tomographic perspective that emphasizes the relation of the many-body spectrum to the underlying classical phase-space structures. In order to address quantum ergodicity in far-from-equilibrium scenarios of experimental interest, we inspect both local aspects (via Bogoliubov analysis) and global aspects (mixed regular-chaotic dynamics). In particular, we highlight the roles of the two parameters that control metastability, clarify the essential differences between low- and high-dimensional chaos, and show how the dynamical instabilities diminish in the limit of the Gross-Pitaevskii equation. It is somewhat frustrating that with more degrees of freedom, the dynamically metastable islands become better distinct from the ergodic sea, while their borders become ill-defined topologically. This stands in opposition to the very structured phase-space of two-degree-of-freedom systems, as reflected in the tomographic quantum spectrum.

quant-pharXiv:2603.23109•Physical Review Research•Mar 25, 2026•0 citations

Mesoscopic superfluid to superconductor transition

Yehoshua Winsten, Doron Cohen

Spectrum tomography for the energy ($E$) of a ring-shaped Bose-Hubbard circuit is illustrated. There is an inter-particle interaction $U$ that controls superfluidity (SF) and the transition to the Mott Insulator (MI) regime. The circuit is coupled to an electromagnetic cavity mode of frequency $ω_0$, and the coupling is characterized by a generalized fine-structure-constant $α$ that controls the emergence of superconductivity (SC). The ${(U,α,ω_0,E)}$ diagram features SF and SC regions, a vast region of fragmented possibly chaotic states, and an MI regime for large $U$. The mesoscopic version of the Meissner effect and the Anderson-Higgs mechanism are discussed.

cond-mat.mes-hallCross-listedarXiv:2512.07632•Physical Review A•Dec 9, 2025•0 citations

Selective Control and Imaging of Higgs and Goldstone Modes with a Quantum Simulator

Connie Miao, Pranjal Praneel, Thomas G. Kiely +5 more

We realize the mesoscopic Bose-Hubbard model at unit-filling on a two-dimensional array of transmon qubits and selectively excite collective modes associated with amplitude or phase fluctuations of the superfluid order parameter. We identify these modes respectively as the Higgs and Goldstone modes using complementary local observables, extracted from measuring the number of particles on each site. Modulation of the coupling between sites excites the Higgs mode, which we detect via the density of doubly occupied sites. In contrast, modulation of the local chemical potential with an appropriately chosen spatial profile excites the lowest-frequency Goldstone mode, which we detect via changes in the local density. The two modes have different symmetries and do not couple to one another. By varying the system geometry, we characterize the impact of finite system size on the evolution of both modes. In the thermodynamic limit, decay into a continuum of lower-energy excitations can obscure the Higgs response. In our mesoscopic system, however, the finite system size leads to spectral gaps and allows us to detect the Higgs mode as a coherent, long-lived excitation. Our work demonstrates how finite quantum simulators can isolate and probe physical phenomena that become difficult to resolve in the thermodynamic, large-scale limit.

quant-pharXiv:2610.19219•Oct 15, 2026•0 citations

Triangular Bose-Hubbard trimer as a minimal model for a superfluid circuit

Geva Arwas, Amichay Vardi, Doron Cohen

The triangular Bose-Hubbard trimer is topologically the minimal model for a BEC superfluid circuit. As a dynamical system of two coupled freedoms it has mixed phase space with chaotic dynamics. We employ a semiclassical perspective to study triangular trimer physics beyond the conventional picture of the superfluid-to-insulator transition. From the analysis of the Peierls-Nabarro energy landscape, we deduce the various regimes in the $(\ensuremath{\Omega},u)$ parameter space, where $u$ is the interaction and $\ensuremath{\Omega}$ is the superfluid rotation-velocity. We thus characterize the superfluid stability and chaoticity of the many-body eigenstates throughout the Hilbert space.

arXiv:1308.5860•Physical Review A•Jan 6, 2014•30 citations

Gaussian quantum fluctuations in the superfluid–Mott-insulator phase transition

Marco Faccioli, Luca Salasnich

Recent advances in cooling techniques make possible the experimental study of quantum phase transitions, which are transitions near absolute zero temperature accessed by varying a control parameter. A paradigmatic example is the superfluid-Mott transition of interacting bosons on a periodic lattice. From the relativistic Ginzburg-Landau action of this superfluid-Mott transition we derive the elementary excitations of the bosonic system, which contain in the superfluid phase a gapped Higgs mode and a gapless Goldstone mode. We show that this energy spectrum is in good agreement with the available experimental data and we use it to extract, with the help of dimensional regularization, meaningful analytical formulas for the beyond-mean-field equation of state in two and three spatial dimensions. We find that, while the mean-field equation of state always gives a second-order quantum phase transition, the inclusion of Gaussian quantum fluctuations can induce a first-order quantum phase transition. This prediction is a strong benchmark for future experiments on quantum phase transitions.

arXiv:1808.09338•Physical Review A•Feb 11, 2019•6 citations

Chaos and two-level dynamics of the atomtronic quantum interference device

Geva Arwas, Doron Cohen

We study the atomtronic quantum interference device employing a semiclassical perspective. We consider an M site ring that is described by the Bose–Hubbard Hamiltonian. Coherent Rabi oscillations in the flow of the current are feasible, with an enhanced frequency due to chaos-assisted tunneling. We highlight the consequences of introducing a weak-link into the circuit. In the latter context we clarify the phase–space considerations that are involved in setting up an effective 'systems plus bath' description in terms of Josephson–Caldeira–Leggett Hamiltonian.

arXiv:1510.04438•New Journal of Physics•Jan 11, 2016•16 citations
We provide a phase-space perspective for the analysis of the superfluid-insulator transition for finite-size Bose-Hubbard circuits. We explore how the eigenstates parametrically evolve as the inter-particle interaction is varied, paying attention to the fingerprints of chaos at the quantum phase-transition. Consequently, we demonstrate that the tomographic spectrum reflects the existence of mixed-regions of chaos and quasi-regular motion in phase-space. This tomographic semiclassical approach is much more efficient and informative compared to the traditional "level statistics" inspection. Of particular interest is the characterization of the fluctuations that are exhibited by the many-body eigenstates. In this context, we associate with each eigenstate a Higgs measure for the identification of amplitude modes of the order-parameter. Finally we focus on the formation of the lowest Goldstone and Higgs bands.
We analyze the metastability of Bose-Hubbard condensates for finite-size one-dimensional ring lattices and open chains, using a semiclassical tomographic perspective that emphasizes the relation of the many-body spectrum to the underlying classical phase-space structures. In order to address quantum ergodicity in far-from-equilibrium scenarios of experimental interest, we inspect both local aspects (via Bogoliubov analysis) and global aspects (mixed regular-chaotic dynamics). In particular, we highlight the roles of the two parameters that control metastability, clarify the essential differences between low- and high-dimensional chaos, and show how the dynamical instabilities diminish in the limit of the Gross-Pitaevskii equation. It is somewhat frustrating that with more degrees of freedom, the dynamically metastable islands become better distinct from the ergodic sea, while their borders become ill-defined topologically. This stands in opposition to the very structured phase-space of two-degree-of-freedom systems, as reflected in the tomographic quantum spectrum.
Spectrum tomography for the energy (EEE) of a ring-shaped Bose-Hubbard circuit is illustrated. There is an inter-particle interaction UUU that controls superfluidity (SF) and the transition to the Mott Insulator (MI) regime. The circuit is coupled to an electromagnetic cavity mode of frequency ω0ω_0ω0​, and the coupling is characterized by a generalized fine-structure-constant ααα that controls the emergence of superconductivity (SC). The (U,α,ω0,E){(U,α,ω_0,E)}(U,α,ω0​,E) diagram features SF and SC regions, a vast region of fragmented possibly chaotic states, and an MI regime for large UUU. The mesoscopic version of the Meissner effect and the Anderson-Higgs mechanism are discussed.
We realize the mesoscopic Bose-Hubbard model at unit-filling on a two-dimensional array of transmon qubits and selectively excite collective modes associated with amplitude or phase fluctuations of the superfluid order parameter. We identify these modes respectively as the Higgs and Goldstone modes using complementary local observables, extracted from measuring the number of particles on each site. Modulation of the coupling between sites excites the Higgs mode, which we detect via the density of doubly occupied sites. In contrast, modulation of the local chemical potential with an appropriately chosen spatial profile excites the lowest-frequency Goldstone mode, which we detect via changes in the local density. The two modes have different symmetries and do not couple to one another. By varying the system geometry, we characterize the impact of finite system size on the evolution of both modes. In the thermodynamic limit, decay into a continuum of lower-energy excitations can obscure the Higgs response. In our mesoscopic system, however, the finite system size leads to spectral gaps and allows us to detect the Higgs mode as a coherent, long-lived excitation. Our work demonstrates how finite quantum simulators can isolate and probe physical phenomena that become difficult to resolve in the thermodynamic, large-scale limit.
The triangular Bose-Hubbard trimer is topologically the minimal model for a BEC superfluid circuit. As a dynamical system of two coupled freedoms it has mixed phase space with chaotic dynamics. We employ a semiclassical perspective to study triangular trimer physics beyond the conventional picture of the superfluid-to-insulator transition. From the analysis of the Peierls-Nabarro energy landscape, we deduce the various regimes in the $(\ensuremath{\Omega},u)$ parameter space, where uuu is the interaction and $\ensuremath{\Omega}$ is the superfluid rotation-velocity. We thus characterize the superfluid stability and chaoticity of the many-body eigenstates throughout the Hilbert space.
Recent advances in cooling techniques make possible the experimental study of quantum phase transitions, which are transitions near absolute zero temperature accessed by varying a control parameter. A paradigmatic example is the superfluid-Mott transition of interacting bosons on a periodic lattice. From the relativistic Ginzburg-Landau action of this superfluid-Mott transition we derive the elementary excitations of the bosonic system, which contain in the superfluid phase a gapped Higgs mode and a gapless Goldstone mode. We show that this energy spectrum is in good agreement with the available experimental data and we use it to extract, with the help of dimensional regularization, meaningful analytical formulas for the beyond-mean-field equation of state in two and three spatial dimensions. We find that, while the mean-field equation of state always gives a second-order quantum phase transition, the inclusion of Gaussian quantum fluctuations can induce a first-order quantum phase transition. This prediction is a strong benchmark for future experiments on quantum phase transitions.
We study the atomtronic quantum interference device employing a semiclassical perspective. We consider an M site ring that is described by the Bose–Hubbard Hamiltonian. Coherent Rabi oscillations in the flow of the current are feasible, with an enhanced frequency due to chaos-assisted tunneling. We highlight the consequences of introducing a weak-link into the circuit. In the latter context we clarify the phase–space considerations that are involved in setting up an effective 'systems plus bath' description in terms of Josephson–Caldeira–Leggett Hamiltonian.