Article records
https://feeds.library.caltech.edu/people/Cao-ChunJun/article.rss
A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenTue, 16 Apr 2024 13:25:53 +0000Consistency conditions for an AdS multiscale entanglement renormalization ansatz correspondence
https://resolver.caltech.edu/CaltechAUTHORS:20150601-131525807
Authors: {'items': [{'id': 'Bao-Ning', 'name': {'family': 'Bao', 'given': 'Ning'}, 'orcid': '0000-0002-3296-1039'}, {'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Carroll-S-M', 'name': {'family': 'Carroll', 'given': 'Sean M.'}, 'orcid': '0000-0002-4226-5758'}, {'id': 'Chatwin-Davies-A', 'name': {'family': 'Chatwin-Davies', 'given': 'Aidan'}, 'orcid': '0000-0003-1406-9271'}, {'id': 'Hunter-Jones-N', 'name': {'family': 'Hunter-Jones', 'given': 'Nicholas'}}, {'id': 'Pollack-J-A', 'name': {'family': 'Pollack', 'given': 'Jason'}, 'orcid': '0000-0003-4754-4905'}, {'id': 'Remmen-G-N', 'name': {'family': 'Remmen', 'given': 'Grant N.'}, 'orcid': '0000-0001-6569-8866'}]}
Year: 2015
DOI: 10.1103/PhysRevD.91.125036
The multiscale entanglement renormalization ansatz (MERA) is a tensor network that provides an efficient way of variationally estimating the ground state of a critical quantum system. The network geometry resembles a discretization of spatial slices of an anti–de Sitter (AdS) spacetime and "geodesics" in the MERA reproduce the Ryu-Takayanagi formula for the entanglement entropy of a boundary region in terms of bulk properties. It has therefore been suggested that there could be an AdS/MERA correspondence, relating states in the Hilbert space of the boundary quantum system to ones defined on the bulk lattice. Here we investigate this proposal and derive necessary conditions for it to apply, using geometric features and entropy inequalities that we expect to hold in the bulk. We show that, perhaps unsurprisingly, the MERA lattice can only describe physics on length scales larger than the AdS radius. Further, using the covariant entropy bound in the bulk, we show that there are no conventional MERA parameters that completely reproduce bulk physics even on super-AdS scales. We suggest modifications or generalizations of this kind of tensor network that may be able to provide a more robust correspondence.https://authors.library.caltech.edu/records/c0qbf-wrx40Holographic entropy inequalities and gapped phases of matter
https://resolver.caltech.edu/CaltechAUTHORS:20150812-144213214
Authors: {'items': [{'id': 'Bao-Ning', 'name': {'family': 'Bao', 'given': 'Ning'}, 'orcid': '0000-0002-3296-1039'}, {'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Walter-M', 'name': {'family': 'Walter', 'given': 'Michael'}}, {'id': 'Wang-Zitao', 'name': {'family': 'Wang', 'given': 'Zitao'}, 'orcid': '0000-0002-2326-2674'}]}
Year: 2015
DOI: 10.1007/JHEP09(2015)203
We extend our studies of holographic entropy inequalities to gapped phases of matter. For any number of regions, we determine the linear entropy inequalities satisfied by systems in which the entanglement entropy satisfies an exact area law. In particular, we find that all holographic entropy inequalities are valid in such systems. In gapped systems with topological order, the "cyclic inequalities" derived recently for the holo-graphic entanglement entropy generalize the Kitaev-Preskill formula for the topological entanglement entropy. Finally, we propose a candidate linear inequality for general 4-party quantum states.https://authors.library.caltech.edu/records/m2vmw-r4x37Aharonov-Bohm phases in a quantum LC circuit
https://resolver.caltech.edu/CaltechAUTHORS:20160426-103346757
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Yao-Yuan', 'name': {'family': 'Yao', 'given': 'Yuan'}}, {'id': 'Zhitnitsky-A-R', 'name': {'family': 'Zhitnitsky', 'given': 'Ariel R.'}}]}
Year: 2016
DOI: 10.1103/PhysRevD.93.065049
We study novel types of contributions to the partition function of the Maxwell system defined on a small compact manifold. These contributions, often not addressed in the perturbative treatment with physical photons, emerge as a result of tunneling transitions between topologically distinct but physically identical vacuum winding states. These new terms give an extra contribution to the Casimir pressure, yet to be measured. We argue that this effect is highly sensitive to a small external electric field, which should be contrasted with the conventional Casimir effect, where the vacuum photons are essentially unaffected by any external field. Furthermore, photons will be emitted from the vacuum in response to a time-dependent electric field, similar to the dynamical Casimir effect in which real particles are radiated from the vacuum due to the time-dependent boundary conditions. We also propose an experimental setup using a quantum LC circuit to detect this novel effect. We expect physical electric charges to appear on the capacitor plates when the system dimension is such that coherent Aharonov-Bohm phases can be maintained over macroscopically large distances.https://authors.library.caltech.edu/records/h21bb-s9q51Space from Hilbert Space: Recovering Geometry from Bulk Entanglement
https://resolver.caltech.edu/CaltechAUTHORS:20160704-200753575
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Carroll-S-M', 'name': {'family': 'Carroll', 'given': 'Sean M.'}, 'orcid': '0000-0002-4226-5758'}, {'id': 'Michalakis-S', 'name': {'family': 'Michalakis', 'given': 'Spyridon'}, 'orcid': '0000-0003-4963-1156'}]}
Year: 2017
DOI: 10.1103/PhysRevD.95.024031
We examine how to construct a spatial manifold and its geometry from the entanglement structure of an abstract quantum state in Hilbert space. Given a decomposition of Hilbert space H into a tensor product of factors, we consider a class of "redundancy-constrained states" in H that generalize the area-law behavior for entanglement entropy usually found in condensed-matter systems with gapped local Hamiltonians. Using mutual information to define a distance measure on the graph, we employ classical multidimensional scaling to extract the best-fit spatial dimensionality of the emergent geometry. We then show that entanglement perturbations on such emergent geometries naturally give rise to local modifications of spatial curvature which obey a (spatial) analog of Einstein's equation. The Hilbert space corresponding to a region of flat space is finite-dimensional and scales as the volume, though the entropy (and the maximum change thereof) scales like the area of the boundary. A version of the ER=EPR conjecture is recovered, in that perturbations that entangle distant parts of the emergent geometry generate a configuration that may be considered as a highly quantum wormhole.https://authors.library.caltech.edu/records/957ax-76c67Axion detection via Topological Casimir Effect
https://resolver.caltech.edu/CaltechAUTHORS:20170209-150222935
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Zhitnitsky-A-R', 'name': {'family': 'Zhitnitsky', 'given': 'Ariel'}}]}
Year: 2017
DOI: 10.1103/PhysRevD.96.015013
We propose a new table-top experimental configuration for the direct detection of dark matter QCD axions in the traditional open mass window 10^(-6) eV ≲ m_a ≲ 10^(-2) eV using nonperturbative effects in a system with nontrivial spatial topology. Different from most experimental setups found in literature on direct dark matter axion detection, which relies on ˙θ or ⃗∇θ, we found that our system is in principle sensitive to a static θ ≥ 10^(-14) and can also be used to set limit on the fundamental constant θ_(QED) which becomes the fundamental observable parameter of the Maxwell system if some conditions are met. Furthermore, the proposed experiments can probe entire open mass window 10^(-6) eV ≲ m_a ≲10^(-2) eV with the same design, which should be contrasted with conventional cavity-type experiments being sensitive to a specific axion mass. Connection with Witten effect when the induced electric charge e′ is proportional to θ and the magnetic monopole becomes the dyon with nonvanishing e′ = -eθ/2π is also discussed.https://authors.library.caltech.edu/records/85wjh-qxt55de Sitter space as a tensor network: Cosmic no-hair, complementarity, and complexity
https://resolver.caltech.edu/CaltechAUTHORS:20180105-090200316
Authors: {'items': [{'id': 'Bao-Ning', 'name': {'family': 'Bao', 'given': 'Ning'}, 'orcid': '0000-0002-3296-1039'}, {'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Carroll-S-M', 'name': {'family': 'Carroll', 'given': 'Sean M.'}, 'orcid': '0000-0002-4226-5758'}, {'id': 'Chatwin-Davies-A', 'name': {'family': 'Chatwin-Davies', 'given': 'Aidan'}, 'orcid': '0000-0003-1406-9271'}]}
Year: 2017
DOI: 10.1103/PhysRevD.96.123536
We investigate the proposed connection between de Sitter spacetime and the multiscale entanglement renormalization ansatz (MERA) tensor network, and ask what can be learned via such a construction. We show that the quantum state obeys a cosmic no-hair theorem: the reduced density operator describing a causal patch of the MERA asymptotes to a fixed point of a quantum channel, just as spacetimes with a positive cosmological constant asymptote to de Sitter space. The MERA is potentially compatible with a weak form of complementarity (local physics only describes single patches at a time, but the overall Hilbert space is infinite dimensional) or, with certain specific modifications to the tensor structure, a strong form (the entire theory describes only a single patch plus its horizon, in a finite-dimensional Hilbert space). We also suggest that de Sitter evolution has an interpretation in terms of circuit complexity, as has been conjectured for anti–de Sitter space.https://authors.library.caltech.edu/records/15h82-hak05Bulk Entanglement Gravity without a Boundary: Towards Finding Einstein's Equation in Hilbert Space
https://resolver.caltech.edu/CaltechAUTHORS:20171214-111114409
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Carroll-S-M', 'name': {'family': 'Carroll', 'given': 'Sean M.'}, 'orcid': '0000-0002-4226-5758'}]}
Year: 2018
DOI: 10.1103/PhysRevD.97.086003
We consider the emergence from quantum entanglement of spacetime geometry in a bulk region. For certain classes of quantum states in an appropriately factorized Hilbert space, a spatial geometry can be defined by associating areas along codimension-one surfaces with the entanglement entropy between either side. We show how radon transforms can be used to convert these data into a spatial metric. Under a particular set of assumptions, the time evolution of such a state traces out a four-dimensional spacetime geometry, and we argue using a modified version of Jacobson's "entanglement equilibrium" that the geometry should obey Einstein's equation in the weak-field limit. We also discuss how entanglement equilibrium is related to a generalization of the Ryu-Takayanagi formula in more general settings, and how quantum error correction can help specify the emergence map between the full quantum-gravity Hilbert space and the semiclassical limit of quantum fields propagating on a classical spacetime.https://authors.library.caltech.edu/records/2m2vx-01829Towards bulk metric reconstruction from extremal area variations
https://resolver.caltech.edu/CaltechAUTHORS:20190820-131613485
Authors: {'items': [{'id': 'Bao-Ning', 'name': {'family': 'Bao', 'given': 'Ning'}, 'orcid': '0000-0002-3296-1039'}, {'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Fischetti-S', 'name': {'family': 'Fischetti', 'given': 'Sebastian'}, 'orcid': '0000-0002-2783-211X'}, {'id': 'Keeler-C', 'name': {'family': 'Keeler', 'given': 'Cynthia'}, 'orcid': '0000-0002-4248-3704'}]}
Year: 2019
DOI: 10.1088/1361-6382/ab377f
The Ryu–Takayanagi and Hubeny–Rangamani–Takayanagi formulae suggest that bulk geometry emerges from the entanglement structure of the boundary theory. Using these formulae, we build on a result of Alexakis, Balehowsky, and Nachman to show that in four bulk dimensions, the entanglement entropies of boundary regions of disk topology uniquely fix the bulk metric in any region foliated by the corresponding HRT surfaces. More generally, for a bulk of any dimension d ⩾ 4, knowledge of the (variations of the) areas of two-dimensional boundary-anchored extremal surfaces of disk topology uniquely fixes the bulk metric wherever these surfaces reach. This result is covariant and not reliant on any symmetry assumptions; its applicability thus includes regions of strong dynamical gravity such as the early-time interior of black holes formed from collapse. While we only show uniqueness of the metric, the approach we present provides a clear path towards an explicitspacetime metric reconstruction.https://authors.library.caltech.edu/records/rr3er-x6z29How Low Can Vacuum Energy Go When Your Fields Are Finite-Dimensional?
https://resolver.caltech.edu/CaltechAUTHORS:20190709-152651012
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Chatwin-Davies-A', 'name': {'family': 'Chatwin-Davies', 'given': 'Aidan'}, 'orcid': '0000-0003-1406-9271'}, {'id': 'Singh-Ashmeet', 'name': {'family': 'Singh', 'given': 'Ashmeet'}, 'orcid': '0000-0002-4404-1416'}]}
Year: 2019
DOI: 10.1142/S0218271819440061
According to the holographic bound, there is only a finite density of degrees of freedom in space when gravity is taken into account. Conventional quantum field theory does not conform to this bound, since in this framework, infinitely many degrees of freedom may be localized to any given region of space. In this paper, we explore the viewpoint that quantum field theory may emerge from an underlying theory that is locally finite-dimensional, and we construct a locally finite-dimensional version of a Klein–Gordon scalar field using generalized Clifford algebras. Demanding that the finite-dimensional field operators obey a suitable version of the canonical commutation relations makes this construction essentially unique. We then find that enforcing local finite dimensionality in a holographically consistent way leads to a huge suppression of the quantum contribution to vacuum energy, to the point that the theoretical prediction becomes plausibly consistent with observations.https://authors.library.caltech.edu/records/htz2k-4gv03Building bulk geometry from the tensor Radon transform
https://resolver.caltech.edu/CaltechAUTHORS:20201216-103316521
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Qi-Xiao-Liang', 'name': {'family': 'Qi', 'given': 'Xiao-Liang'}}, {'id': 'Swingle-Brian', 'name': {'family': 'Swingle', 'given': 'Brian'}, 'orcid': '0000-0003-0334-3108'}, {'id': 'Tang-Eugene', 'name': {'family': 'Tang', 'given': 'Eugene'}}]}
Year: 2020
DOI: 10.1007/JHEP12(2020)033
Using the tensor Radon transform and related numerical methods, we study how bulk geometries can be explicitly reconstructed from boundary entanglement entropies in the specific case of AdS₃/CFT₂. We find that, given the boundary entanglement entropies of a 2d CFT, this framework provides a quantitative measure that detects whether the bulk dual is geometric in the perturbative (near AdS) limit. In the case where a well-defined bulk geometry exists, we explicitly reconstruct the unique bulk metric tensor once a gauge choice is made. We then examine the emergent bulk geometries for static and dynamical scenarios in holography and in many-body systems. Apart from the physics results, our work demonstrates that numerical methods are feasible and effective in the study of bulk reconstruction in AdS/CFT.https://authors.library.caltech.edu/records/3abrh-f1240Large N matrix quantum mechanics as a quantum memory
https://authors.library.caltech.edu/records/ry5h5-d6y89
Authors: {'items': [{'id': 'Cao-ChunJun', 'name': {'family': 'Cao', 'given': 'ChunJun'}, 'orcid': '0000-0002-5761-5474'}, {'id': 'Cheng-Gong', 'name': {'family': 'Cheng', 'given': 'Gong'}, 'orcid': '0009-0008-9158-7404'}, {'id': 'Swingle-Brian', 'name': {'family': 'Swingle', 'given': 'Brian'}, 'orcid': '0000-0003-0334-3108'}]}
Year: 2023
DOI: 10.1103/physrevd.108.086008
<p>In this paper, we explore the possibility of building a quantum memory that is robust to thermal noise using large N matrix quantum mechanics models. First, we investigate the gauged SU(<i>N</i>) matrix harmonic oscillator and different ways to encode quantum information in it. By calculating the mutual information between the system and a reference which purifies the encoded information, we identify a transition temperature, T_c, below which the encoded quantum information is protected from thermal noise for a memory time scaling as <i>N</i>². Conversely, for temperatures higher than T_c, the information is quickly destroyed by thermal noise. Second, we relax the requirement of gauge invariance and study a matrix harmonic oscillator model with only global symmetry. Finally, we further relax even the symmetry requirement and propose a model that consists of a large number <i>N</i>² of qubits, with interactions derived from an approximate SU(<i>N</i>) symmetry. In both ungauged models, we find that the effects of gauging can be mimicked using an energy penalty to give a similar result for the memory time. The final qubit model also has the potential to be realized in the laboratory.</p>https://authors.library.caltech.edu/records/ry5h5-d6y89