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  1. Article ; Online: Tuning Superinductors by Quantum Coherence Effects for Enhancing Quantum Computing.

    Fan, Bo / Samanta, Abhisek / García-García, Antonio M

    Physical review letters

    2023  Volume 130, Issue 4, Page(s) 47001

    Abstract: Research on spatially inhomogeneous weakly coupled superconductors has recently received a boost of interest because of the experimental observation of a dramatic enhancement of the kinetic inductance with relatively low losses. Here, we study the ... ...

    Abstract Research on spatially inhomogeneous weakly coupled superconductors has recently received a boost of interest because of the experimental observation of a dramatic enhancement of the kinetic inductance with relatively low losses. Here, we study the kinetic inductance and the quality factor of a strongly disordered, weakly coupled superconducting thin film. We employ a gauge-invariant random-phase approximation capable of describing collective excitations and other fluctuations. In line with the experimental findings, we have found that in the range of frequencies of interest, and for sufficiently low temperatures, an exponential increase of the kinetic inductance with disorder coexists with a still large quality factor of ∼10^{4}. More interestingly, on the metallic side of the superconductor-insulator transition, we have identified a range of frequencies and temperatures, T∼0.1T_{c}, where quantum coherence effects induce a broad statistical distribution of the quality factor with an average value that increases with disorder. We expect these findings to further stimulate experimental research on the design and optimization of superinductors for a better performance and miniaturization of quantum devices such as qubit circuits and microwave detectors.
    Language English
    Publishing date 2023-02-10
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.130.047001
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  2. Article ; Online: Sixfold Way of Traversable Wormholes in the Sachdev-Ye-Kitaev Model.

    García-García, Antonio M / Sá, Lucas / Verbaarschot, Jacobus J M / Yin, Can

    Physical review letters

    2024  Volume 132, Issue 6, Page(s) 61603

    Abstract: In the infrared limit, a nearly anti-de Sitter spacetime in two dimensions (AdS_{2}) perturbed by a weak double trace deformation and a two-site (q>2)-body Sachdev-Ye-Kitaev (SYK) model with N Majoranas and a weak 2r-body intersite coupling share the ... ...

    Abstract In the infrared limit, a nearly anti-de Sitter spacetime in two dimensions (AdS_{2}) perturbed by a weak double trace deformation and a two-site (q>2)-body Sachdev-Ye-Kitaev (SYK) model with N Majoranas and a weak 2r-body intersite coupling share the same near-conformal dynamics described by a traversable wormhole. We exploit this relation to propose a symmetry classification of traversable wormholes depending on N, q, and r, with q>2r, and confirm it by a level statistics analysis using exact diagonalization techniques. Intriguingly, a time-reversed state never results in a new state, so only six universality classes occur-A, AI, BDI, CI, C, and D-and different symmetry sectors of the model may belong to distinct universality classes.
    Language English
    Publishing date 2024-02-23
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.132.061603
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  3. Book ; Online: Sparsity independent Lyapunov exponent in the Sachdev-Ye-Kitaev model

    García-García, Antonio M. / Liu, Chang / Verbaarschot, Jacobus J. M.

    2023  

    Abstract: The saturation of a recently proposed universal bound on the Lyapunov exponent has been conjectured to signal the existence of a gravity dual. This saturation occurs in the low temperature limit of the dense Sachdev-Ye-Kitaev (SYK) model, $N$ Majorana ... ...

    Abstract The saturation of a recently proposed universal bound on the Lyapunov exponent has been conjectured to signal the existence of a gravity dual. This saturation occurs in the low temperature limit of the dense Sachdev-Ye-Kitaev (SYK) model, $N$ Majorana fermions with $q$-body ($q>2$) infinite-range interactions. We calculate certain Out of Time Order Correlators (OTOC) for $N\le 64$ fermions for a highly sparse SYK model and find no significant dependence of the Lyapunov exponent on sparsity up to near the percolation limit where the Hamiltonian breaks up into blocks. This suggests that in the sparse case, the Lyapunov exponent also saturates the low-temperature bound. A key ingredient to reaching $N = 64$ is the development of a novel quantum spin model simulation library that implements highly-optimized matrix-free Krylov subspace methods on Graphical Processing Units (GPUs). This leads to a significantly lower simulation time as well as vastly reduced memory usage over previous approaches, while using modest computational resources. Strong sparsity-driven statistical fluctuations require both the use of a vastly larger number of disorder realizations with respect to the dense limit and a careful finite size scaling analysis. Our results potentially broadens the landscape of theories that may have a gravity analogue.

    Comment: 8 pages, 6 figures
    Keywords High Energy Physics - Theory ; Condensed Matter - Disordered Systems and Neural Networks ; Quantum Physics
    Subject code 612
    Publishing date 2023-11-01
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Dominance of Replica Off-Diagonal Configurations and Phase Transitions in a PT Symmetric Sachdev-Ye-Kitaev Model.

    García-García, Antonio M / Jia, Yiyang / Rosa, Dario / Verbaarschot, Jacobus J M

    Physical review letters

    2022  Volume 128, Issue 8, Page(s) 81601

    Abstract: We show that, after ensemble averaging, the low temperature phase of a conjugate pair of uncoupled, quantum chaotic, non-Hermitian systems such as the Sachdev-Ye-Kitaev (SYK) model or the Ginibre ensemble of random matrices is dominated by saddle points ... ...

    Abstract We show that, after ensemble averaging, the low temperature phase of a conjugate pair of uncoupled, quantum chaotic, non-Hermitian systems such as the Sachdev-Ye-Kitaev (SYK) model or the Ginibre ensemble of random matrices is dominated by saddle points that couple replicas and conjugate replicas. This results in a nearly flat free energy that terminates in a first-order phase transition. In the case of the SYK model, we show explicitly that the spectrum of the effective replica theory has a gap. These features are strikingly similar to those induced by wormholes in the gravity path integral which suggests a close relation between both configurations. For a nonchaotic SYK, the results are qualitatively different: the spectrum is gapless in the low temperature phase and there is an infinite number of second order phase transitions unrelated to the restoration of replica symmetry.
    Language English
    Publishing date 2022-03-11
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.128.081601
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: Tuning Superinductors by Quantum Coherence Effects for Enhancing Quantum Computing

    Fan, Bo / Samanta, Abhisek / García-García, Antonio M.

    2021  

    Abstract: Research on spatially inhomogeneous weakly-coupled superconductors has recently received a boost of interest because of the experimental observation of a dramatic enhancement of the kinetic inductance with relatively low losses. Here, we study the ... ...

    Abstract Research on spatially inhomogeneous weakly-coupled superconductors has recently received a boost of interest because of the experimental observation of a dramatic enhancement of the kinetic inductance with relatively low losses. Here, we study the kinetic inductance and the quality factor of a strongly-disordered weakly-coupled superconducting thin film. We employ a gauge-invariant random-phase approximation capable of describing collective excitations and other fluctuations. In line with the experimental findings, we have found that in the range of frequencies of interest, and for sufficiently low temperatures, an exponential increase of the kinetic inductance with disorder coexists with a still large quality factor $\sim 10^4$. More interestingly, on the metallic side of the superconductor-insulator transition, we have identified a range of frequencies and temperatures $T \sim 0.1T_c$ where quantum coherence effects induce a broad statistical distribution of the quality factor with an average value that increases with disorder. We expect these findings to further stimulate experimental research on the design and optimization of superinductors for a better performance and miniaturization of quantum devices such as qubit circuits and microwave detectors.

    Comment: 18 pages, 12 figures, v2: update manuscript, version as published
    Keywords Condensed Matter - Superconductivity
    Subject code 612
    Publishing date 2021-12-22
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: García-García et al. Reply.

    García-García, Antonio M / Loureiro, Bruno / Romero-Bermúdez, Aurelio / Tezuka, Masaki

    Physical review letters

    2021  Volume 126, Issue 10, Page(s) 109102

    Language English
    Publishing date 2021-03-30
    Publishing country United States
    Document type Journal Article ; Comment
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.126.109102
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  7. Book ; Online: Many-Body Localization in a finite-range Sachdev-Ye-Kitaev model

    García-García, Antonio M. / Tezuka, Masaki

    2018  

    Abstract: We study the level statistics of a generalized Sachdev-Ye-Kitaev (SYK) model with two-body and one-body random interactions of finite range by exact diagonalization. Tuning the range of the one-body term, while keeping the two-body interaction ... ...

    Abstract We study the level statistics of a generalized Sachdev-Ye-Kitaev (SYK) model with two-body and one-body random interactions of finite range by exact diagonalization. Tuning the range of the one-body term, while keeping the two-body interaction sufficiently long-ranged, does not alter substantially the spectral correlations, which are still given by the random matrix prediction typical of a quantum chaotic system. However a transition to an insulating state, characterized by Poisson statistics, is observed by reducing the range of the two-body interaction. Close to the many-body metal-insulator transition, we show that spectral correlations share all features previously found in systems at the Anderson transition and in the proximity of the many-body localization transition. Our results suggest the potential relevance of SYK models in the context of many-body localization and also offer a starting point for the exploration of a gravity-dual of this phenomenon.

    Comment: 6 pages, 2 figures
    Keywords High Energy Physics - Theory ; Condensed Matter - Disordered Systems and Neural Networks ; Condensed Matter - Strongly Correlated Electrons
    Subject code 612
    Publishing date 2018-01-09
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article: Semiclassical theory of the Anderson transition.

    García-García, Antonio M

    Physical review letters

    2008  Volume 100, Issue 7, Page(s) 76404

    Abstract: We study analytically the metal-insulator transition in a disordered conductor by combining the self-consistent theory of localization with the one parameter scaling theory. We provide explicit expressions of the critical exponents and the critical ... ...

    Abstract We study analytically the metal-insulator transition in a disordered conductor by combining the self-consistent theory of localization with the one parameter scaling theory. We provide explicit expressions of the critical exponents and the critical disorder as a function of the spatial dimensionality d. The critical exponent nu controlling the divergence of the localization length at the transition is found to be nu=1/2+1/d-2 thus confirming that the upper critical dimension is infinity. Level statistics are investigated in detail. We show that the two level correlation function decays exponentially and the number variance is linear with a slope which is an increasing function of the spatial dimensionality. Our analytical findings are in agreement with previous numerical results.
    Language English
    Publishing date 2008-02-22
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.100.076404
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Chaotic-Integrable Transition in the Sachdev-Ye-Kitaev Model.

    García-García, Antonio M / Loureiro, Bruno / Romero-Bermúdez, Aurelio / Tezuka, Masaki

    Physical review letters

    2018  Volume 120, Issue 24, Page(s) 241603

    Abstract: Quantum chaos is one of the distinctive features of the Sachdev-Ye-Kitaev (SYK) model, N Majorana fermions in 0+1 dimensions with infinite-range two-body interactions, which is attracting a lot of interest as a toy model for holography. Here we show ... ...

    Abstract Quantum chaos is one of the distinctive features of the Sachdev-Ye-Kitaev (SYK) model, N Majorana fermions in 0+1 dimensions with infinite-range two-body interactions, which is attracting a lot of interest as a toy model for holography. Here we show analytically and numerically that a generalized SYK model with an additional one-body infinite-range random interaction, which is a relevant perturbation in the infrared, is still quantum chaotic and retains most of its holographic features for a fixed value of the perturbation and sufficiently high temperature. However, a chaotic-integrable transition, characterized by the vanishing of the Lyapunov exponent and spectral correlations given by Poisson statistics, occurs at a temperature that depends on the strength of the perturbation. We speculate about the gravity dual of this transition.
    Language English
    Publishing date 2018-06-28
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.120.241603
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Dissipation in a simple model of a topological Josephson junction.

    Matthews, Paul / Ribeiro, Pedro / García-García, Antonio M

    Physical review letters

    2014  Volume 112, Issue 24, Page(s) 247001

    Abstract: The topological features of low-dimensional superconductors have created a lot of excitement recently because of their broad range of applications in quantum information and their potential to reveal novel phases of quantum matter. A potential problem ... ...

    Abstract The topological features of low-dimensional superconductors have created a lot of excitement recently because of their broad range of applications in quantum information and their potential to reveal novel phases of quantum matter. A potential problem for practical applications is the presence of phase slips that break phase coherence. Dissipation in nontopological superconductors suppresses phase slips and can restore long-range order. Here, we investigate the role of dissipation in a topological Josephson junction. We show that the combined effects of topology and dissipation keep phase and antiphase slips strongly correlated so that the device is superconducting even under conditions where a nontopological device would be resistive. The resistive transition occurs at a critical value of the dissipation that is 4 times smaller than that expected for a conventional Josephson junction. We propose that this difference could be employed as a robust experimental signature of topological superconductivity.
    Language English
    Publishing date 2014-06-20
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.112.247001
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