Observation of energy-resolved many-body localization

Guo, Qiujiang; Cheng, Chen; Sun, Zheng‐Hang; Song, Zixuan; Li, Hekang; Wang, Zhen; Ren, Wenhui; Dong, Hang; Zheng, Dewen; Zhang, Yu-Ran; Mondaini, Rubem; Fan, Heng; Wang, H.

doi:10.1038/s41567-020-1035-1

Cited by 116 publications

(77 citation statements)

References 40 publications

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“…Qubit design and performance. Qubit characterization was performed on transmon qubits, which are widely used for quantum computing and quantum simulation applications 1,10,11,[24][25][26][27][28] . Transmons consist of a Josephson junction-implemented with a thin aluminum oxide barrier between superconducting wiresshunted by a large capacitor (Fig.…”

Section: Resultsmentioning

confidence: 99%

Microscopic relaxation channels in materials for superconducting qubits

et al. 2021

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Despite mounting evidence that materials imperfections are a major obstacle to practical applications of superconducting qubits, connections between microscopic material properties and qubit coherence are poorly understood. Here, we combine measurements of transmon qubit relaxation times (T1) with spectroscopy and microscopy of the polycrystalline niobium films used in qubit fabrication. By comparing films deposited using three different techniques, we reveal correlations between T1 and intrinsic film properties such as grain size, enhanced oxygen diffusion along grain boundaries, and the concentration of suboxides near the surface. Qubit and resonator measurements show signatures of two-level system defects, which we propose to be hosted in the grain boundaries and surface oxides. We also show that the residual resistance ratio of the polycrystalline niobium films can be used as a figure of merit for qubit lifetime. This comprehensive approach to understanding qubit decoherence charts a pathway for materials-driven improvements of superconducting qubit performance.

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Section: Resultsmentioning

confidence: 99%

Microscopic relaxation channels in materials for superconducting qubits

et al. 2021

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“…Hence, a high amount of disorder is not only beneficial for the initial state under consideration; it also reduces the mixing of the redundant records in the presence of intra-environment interactions. At last, we sincerely hope our findings shed new light on how classical objectivity emerges from a quantum world and we look forward to the possibility of implementing our ideas on some of the experimental platforms recently used in the study of the MBL transition [47].…”

Section: Discussionmentioning

confidence: 89%

“…Despite that in this first part we have shown a close relationship between the entanglement of the initial state of the environment and its capability of enabling redundancy, it is important to notice that until now we have restricted entirely to the middle of the spectrum by considering the eigenstate with energy closest to = 0.5 in all simulations. However, the value of the critical disorder h c depends on the energy under consideration, which determines what is called a many-body mobility edge [40][41][42][43][44][45][46][47]50,51]. For this reason, it is worthy to study how our Darwinistic measure LR behaves when considering different eigenstates of ĤE as initial states.…”

Section: Localization In the Initial Statementioning

confidence: 99%

“…To do so, we use as an environmental model a disordered spin chain widely studied in the context of many-body localization (MBL) [38][39][40][41][42][43][44]. This system exhibits an ergodic or a localized behaviour, depending on its energy and disorder strength, which sets a many-body mobility edge that has been estimated both theoretically and experimentally [45][46][47]. Thereby, by coupling a two-level quantum system to this disordered environment, we study the proliferation of redundant information both in the ergodic and localized phase.…”

Section: Introductionmentioning

confidence: 99%

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Many-Body Localization and the Emergence of Quantum Darwinism

Mirkin

Wisniacki

2021

Entropy

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Quantum Darwinism (QD) is the process responsible for the proliferation of redundant information in the environment of a quantum system that is being decohered. This enables independent observers to access separate environmental fragments and reach consensus about the system’s state. In this work, we study the effect of disorder in the emergence of QD and find that a highly disordered environment is greatly beneficial for it. By introducing the notion of lack of redundancy to quantify objectivity, we show that it behaves analogously to the entanglement entropy (EE) of the environmental eigenstate taken as an initial state. This allows us to estimate the many-body mobility edge by means of our Darwinistic measure, implicating the existence of a critical degree of disorder beyond which the degree of objectivity rises the larger the environment is. The latter hints the key role that disorder may play when the environment is of a thermodynamic size. At last, we show that a highly disordered evolution may reduce the spoiling of redundancy in the presence of intra-environment interactions.

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“…Superconducting transmonic devices are the leading platforms for quantum simulations [33,36,54,64]. In this section, we show that our protocol can indeed be realized in such set-ups.…”

Section: Experimental Proposalmentioning

confidence: 82%

Parallel entangling gate operations and two-way quantum communication in spin chains

Yousefjani

Bayat

2021

Quantum

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The power of a quantum circuit is determined through the number of two-qubit entangling gates that can be performed within the coherence time of the system. In the absence of parallel quantum gate operations, this would make the quantum simulators limited to shallow circuits. Here, we propose a protocol to parallelize the implementation of two-qubit entangling gates between multiple users which are spatially separated, and use a commonly shared spin chain data-bus. Our protocol works through inducing effective interaction between each pair of qubits without disturbing the others, therefore, it increases the rate of gate operations without creating crosstalk. This is achieved by tuning the Hamiltonian parameters appropriately, described in the form of two different strategies. The tuning of the parameters makes different bilocalized eigenstates responsible for the realization of the entangling gates between different pairs of distant qubits. Remarkably, the performance of our protocol is robust against increasing the length of the data-bus and the number of users. Moreover, we show that this protocol can tolerate various types of disorders and is applicable in the context of superconductor-based systems. The proposed protocol can serve for realizing two-way quantum communication.

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Observation of energy-resolved many-body localization

Cited by 116 publications

References 40 publications

Microscopic relaxation channels in materials for superconducting qubits

Microscopic relaxation channels in materials for superconducting qubits

Many-Body Localization and the Emergence of Quantum Darwinism

Parallel entangling gate operations and two-way quantum communication in spin chains

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