ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 17 Aug 2022 09:52:03 GMT2022-08-17T09:52:03Z50111- Coherent superposition of current flows in an atomtronic quantum interference devicehttps://scholarbank.nus.edu.sg/handle/10635/175289Title: Coherent superposition of current flows in an atomtronic quantum interference device
Authors: Aghamalyan, D; Cominotti, M; Rizzi, M; Rossini, D; Hekking, F; Minguzzi, A; Kwek, L.-C; Amico, L
Abstract: We consider a correlated Bose gas tightly confined into a ring shaped lattice, in the presence of an artificial gauge potential inducing a persistent current through it. A weak link painted on the ring acts as a source of coherent back-scattering for the propagating gas, interfering with the forward scattered current. This system defines an atomic counterpart of the rf-SQUID: the atomtronics quantum interference device. The goal of the present study is to corroborate the emergence of an effective two-level system in such a setup and to assess its quality, in terms of its inner resolution and its separation from the rest of the many-body spectrum, across the different physical regimes. In order to achieve this aim, we examine the dependence of the qubit energy gap on the bosonic density, the interaction strength, and the barrier depth, and we show how the superposition between current states appears in the momentum distribution (time-of-flight) images. A mesoscopic ring lattice with intermediate-to-strong interactions and weak barrier depth is found to be a favorable candidate for setting up, manipulating and probing a qubit in the next generation of atomic experiments. © 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Thu, 01 Jan 2015 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1752892015-01-01T00:00:00Z
- Local reversibility and entanglement structure of many-body ground stateshttps://scholarbank.nus.edu.sg/handle/10635/178695Title: Local reversibility and entanglement structure of many-body ground states
Authors: Kuwahara, T; Arad, I; Amico, L; Vedral, V
Abstract: The low-temperature physics of quantum many-body systems is largely governed by the structure of their ground states. Minimizing the energy of local interactions, ground states often reflect strong properties of locality such as the area law for entanglement entropy and the exponential decay of correlations between spatially separated observables. Here, we present a novel characterization of quantum states, which we call 'local reversibility'. It characterizes the type of operations that are needed to reverse the action of a general disturbance on the state. We prove that unique ground states of gapped local Hamiltonian are locally reversible. This way, we identify new universal features of many-body ground states, which cannot be derived from the aforementioned properties. We use local reversibility to distinguish between states enjoying microscopic and macroscopic quantum phenomena. To demonstrate the potential of our approach, we prove specific properties of ground states, which are relevant both to critical and non-critical theories. © 2017 IOP Publishing Ltd.
Sun, 01 Jan 2017 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1786952017-01-01T00:00:00Z
- Corrigendum: Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybridhttps://scholarbank.nus.edu.sg/handle/10635/178283Title: Corrigendum: Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybrid
Authors: Yu, D.; Valado, M.M.; Hufnagel, C.; Kwek, L.C.; Amico, L.; Dumke, R.
Abstract: This corrects the article DOI: 10.1038/srep38356.
Sun, 01 Jan 2017 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1782832017-01-01T00:00:00Z
- Local convertibility and the quantum simulation of edge states in many-body systemshttps://scholarbank.nus.edu.sg/handle/10635/183698Title: Local convertibility and the quantum simulation of edge states in many-body systems
Authors: Franchini, F; Cui, J; Amico, L; Fan, H; Gu, M; Korepin, V; Kwek, L.C; Vedral, V
Abstract: In some many-body systems, certain ground-state entanglement (Rényi) entropies increase even as the correlation length decreases. This entanglement nonmonotonicity is a potential indicator of nonclassicality. In this work, we demonstrate that such a phenomenon, known as lack of local convertibility, is due to the edge-state (de)construction occurring in the system. To this end, we employ the example of the Ising chain, displaying an order-disorder quantum phase transition. Employing both analytical and numerical methods, we compute entanglement entropies for various system bipartitions (A|B) and consider ground states with and without Majorana edge states. We find that the thermal ground states, enjoying the Hamiltonian symmetries, show lack of local convertibility if either A or B is smaller than, or of the order of, the correlation length. In contrast, the ordered (symmetry-breaking) ground state is always locally convertible. The edge-state behavior explains all these results and could disclose a paradigm to understand local convertibility in other quantum phases of matter. The connection we establish between convertibility and nonlocal, quantum correlations provides a clear criterion of which features a universal quantum simulator should possess to outperform a classical machine.
Wed, 01 Jan 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1836982014-01-01T00:00:00Z
- Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybridhttps://scholarbank.nus.edu.sg/handle/10635/179779Title: Quantum State Transmission in a Superconducting Charge Qubit-Atom Hybrid
Authors: Yu, D; Valado, M.M; Hufnagel, C; Kwek, L.C; Amico, L; Dumke, R
Abstract: Hybrids consisting of macroscopic superconducting circuits and microscopic components, such as atoms and spins, have the potential of transmitting an arbitrary state between different quantum species, leading to the prospective of high-speed operation and long-time storage of quantum information. Here we propose a novel hybrid structure, where a neutral-atom qubit directly interfaces with a superconducting charge qubit, to implement the qubit-state transmission. The highly-excited Rydberg atom located inside the gate capacitor strongly affects the behavior of Cooper pairs in the box while the atom in the ground state hardly interferes with the superconducting device. In addition, the DC Stark shift of the atomic states significantly depends on the charge-qubit states. By means of the standard spectroscopic techniques and sweeping the gate voltage bias, we show how to transfer an arbitrary quantum state from the superconducting device to the atom and vice versa. © 2016 The Author(s).
Fri, 01 Jan 2016 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1797792016-01-01T00:00:00Z
- Anisotropic Rabi modelhttps://scholarbank.nus.edu.sg/handle/10635/183713Title: Anisotropic Rabi model
Authors: Xie, Q.-T; Cui, S; Cao, J.-P; Amico, L; Fan, H
Abstract: We define the anisotropic Rabi model as the generalization of the spin-boson Rabi model: The Hamiltonian system breaks the parity symmetry; the rotating and counterrotating interactions are governed by two different coupling constants; a further parameter introduces a phase factor in the counterrotating terms. The exact energy spectrum and eigenstates of the generalized model are worked out. The solution is obtained as an elaboration of a recently proposed method for the isotropic limit of the model. In this way, we provide a long-sought solution of a cascade of models with immediate relevance in different physical fields, including (i) quantum optics, a two-level atom in single-mode cross-electric and magnetic fields; (ii) solid-state physics, electrons in semiconductors with Rashba and Dresselhaus spin-orbit coupling; and (iii) mesoscopic physics, Josephson-junction flux-qubit quantum circuits.
Wed, 01 Jan 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1837132014-01-01T00:00:00Z
- Focus on atomtronics-enabled quantum technologieshttps://scholarbank.nus.edu.sg/handle/10635/179233Title: Focus on atomtronics-enabled quantum technologies
Authors: Amico, L; Birkl, G; Boshier, M; Kwek, L.-C
Abstract: Atomtronics is an emerging field in quantum technology that promises to realize 'atomic circuit' architectures exploiting ultra-cold atoms manipulated in versatile micro-optical circuits generated by laser fields of different shapes and intensities or micro-magnetic circuits known as atom chips. Although devising new applications for computation and information transfer is a defining goal of the field, atomtronics wants to enlarge the scope of quantum simulators and to access new physical regimes with novel fundamental science. With this focus issue we want to survey the state of the art of atomtronics-enabled quantum technology. We collect articles on both conceptual and applicative aspects of the field for diverse exploitations, both to extend the scope of the existing atom-based quantum devices and to devise platforms for new routes to quantum technology. © 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Sun, 01 Jan 2017 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1792332017-01-01T00:00:00Z
- Stabilizing Rabi oscillation of a charge qubit via the atomic clock techniquehttps://scholarbank.nus.edu.sg/handle/10635/175127Title: Stabilizing Rabi oscillation of a charge qubit via the atomic clock technique
Authors: Yu, D; Landra, A; Kwek, L.C; Amico, L; Dumke, R
Abstract: We propose a superconducting circuit-atom hybrid, where the Rabi oscillation of single excess Cooper pair in the island is stabilized via the common atomic clock technique. The noise in the superconducting circuit is mapped onto the voltage source which biases the Cooper-pair box via an inductor and a gate capacitor. The fast fluctuations of the gate charge are significantly suppressed by an inductor-capacitor resonator, leading to a long-relaxation-time Rabi oscillation. More importantly, the residual low-frequency fluctuations are further reduced by using the general feedback-control method, in which the voltage bias is stabilized via continuously measuring the dc-Stark-shift-induced atomic Ramsey signal. The stability and coherence time of the resulting charge-qubit Rabi oscillation are both enhanced. The principal structure of this Cooper-pair-box oscillator is studied in detail. © 2018 The Author(s). Published by IOP Publishing Ltd on behalf of Deutsche Physikalische Gesellschaft.
Mon, 01 Jan 2018 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1751272018-01-01T00:00:00Z
- Entanglement convertibility by sweeping through the quantum phases of the alternating bonds XXZ chainhttps://scholarbank.nus.edu.sg/handle/10635/178904Title: Entanglement convertibility by sweeping through the quantum phases of the alternating bonds XXZ chain
Authors: Tzeng, Y.-C; Dai, L; Chung, M.-C; Amico, L; Kwek, L.-C
Abstract: We study the entanglement structure and the topological edge states of the ground state of the spin-1/2 XXZ model with bond alternation. We employ parity-density matrix renormalization group with periodic boundary conditions. The finite-size scaling of Rényi entropies S2 and S? are used to construct the phase diagram of the system. The phase diagram displays three possible phases: Haldane type (an example of symmetry protected topological ordered phases), Classical Dimer and Néel phases, the latter bounded by two continuous quantum phase transitions. The entanglement and non-locality in the ground state are studied and quantified by the entanglement convertibility. We found that, at small spatial scales, the ground state is not convertible within the topological Haldane dimer phase. The phenomenology we observe can be described in terms of correlations between edge states. We found that the entanglement spectrum also exhibits a distinctive response in the topological phase: the effective rank of the reduced density matrix displays a specifically large "susceptibility" in the topological phase. These findings support the idea that although the topological order in the ground state cannot be detected by local inspection, the ground state response at local scale can tell the topological phases apart from the non-topological phases.
Fri, 01 Jan 2016 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1789042016-01-01T00:00:00Z
- An atomtronic flux qubit: A ring lattice of Bose-Einstein condensates interrupted by three weak linkshttps://scholarbank.nus.edu.sg/handle/10635/175252Title: An atomtronic flux qubit: A ring lattice of Bose-Einstein condensates interrupted by three weak links
Authors: Aghamalyan D.; Nguyen N.T.; Auksztol F.; Gan K.S.; Valado M.M.; Condylis P.C.; Kwek L.-C.; Dumke R.; Amico L.
Abstract: We study a physical system consisting of a Bose-Einstein condensate confined to a ring shaped lattice potential interrupted by three weak links. The system is assumed to be driven by an effective flux piercing the ring lattice. By employing path integral techniques, we explore the effective quantum dynamics of the system in a pure quantum phase dynamics regime. Moreover, the effects of the density's quantum fluctuations are studied through exact diagonalization analysis of the spectroscopy of the Bose-Hubbard model. We demonstrate that a clear two-level system emerges by tuning the magnetic flux at degeneracy. The lattice confinement, platform for the condensate, is realized experimentally employing a spatial light modulator. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Fri, 01 Jan 2016 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1752522016-01-01T00:00:00Z
- Topological pumping in Aharonov–Bohm ringshttps://scholarbank.nus.edu.sg/handle/10635/212239Title: Topological pumping in Aharonov–Bohm rings
Authors: Haug, T.; Dumke, R.; Kwek, L.-C.; Amico, L.
Abstract: Topological Thouless pumping and Aharonov–Bohm effect are both fundamental effects enabled by the topological properties of the system. Here, we study both effects together: topological pumping of interacting particles through Aharonov–Bohm rings. This system can prepare highly entangled many-particle states, transport them via topological pumping and interfere with them, revealing a fractional flux quantum. The type of the generated state is revealed by non-trivial Aharonov–Bohm interference patterns that could be used for quantum sensing. The reflections induced by the interference result from transitions between topological bands. Specific bands allow transport with a band gap scaling as the square-root of the particle number. Our system paves a new way for a combined system of state preparation and topological protected transport. © 2019, The Author(s).
Tue, 01 Jan 2019 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/2122392019-01-01T00:00:00Z