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Correlation is magic in electronic structure Hamiltonians
Authors:
Basie Seibert,
Sam Alterman,
Qingfeng Wang,
Feng Qian,
Akimasa Miyake,
Peter J. Love
Abstract:
The gate and qubit requirements of quantum computations of electronic structure have been extensively studied. However, the quantum resources present in electronic ground states, as measured by entanglement and magic, remain less well understood. We study the relationship between correlation in electronic structure Hamiltonians and magic as measured by the 2-stabilizer Renyi entropy (2-SRE). Pertu…
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The gate and qubit requirements of quantum computations of electronic structure have been extensively studied. However, the quantum resources present in electronic ground states, as measured by entanglement and magic, remain less well understood. We study the relationship between correlation in electronic structure Hamiltonians and magic as measured by the 2-stabilizer Renyi entropy (2-SRE). Perturbative calculations show that the 2-SRE of a given state is proportional to its overlap with a reference stabilizer state. In the context of quantum chemistry, this links the magic of electronic structure ground states to their Hartree-Fock weight, an established measure of electronic correlation. We then show that the 2-SRE of post-Hartree-Fock ground states is proportional to the correlation energy they recover. We explore this connection through the contextual subspace (CS) method. We present a theoretical framework showing that the CS method can be used to monotonically vary the magic of approximate CS ground states, and we prove that the correlation energy recovered by the CS ground states is proportional to the magic present in the approximate ground state. We present simulation results using 190 molecular species under Jordan-Wigner encoding at a range of bond lengths. The linear relationships between magic and correlation are robust across the Hamiltonians in our dataset, but break down at bond lengths beyond the Coulson-Fischer point, where Hartree-Fock fails to capture key physical features of the true ground state wavefunction. By establishing linear relationships for both correlation energy and Hartree-Fock reference weight with the 2-SRE, we conclude that for weakly- and moderately-correlated electronic structure Hamiltonians, the correlation is directly represented by 2-SRE, and thus by the magic.
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Submitted 30 June, 2026;
originally announced June 2026.
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Simultaneous thermoosmotic and thermoelectric responses in nanoconfined electrolyte solutions: Effects of nanopore structures and membrane properties
Authors:
Wenyao Zhang,
Muhammad Farhan,
Kai Jiao,
Fang Qian,
Panpan Guo,
Qiuwang Wang,
Charles Chun Yang,
and Cunlu Zhao
Abstract:
Hypothesis: Nanofluidic systems provide an emerging and efficient platform for thermoelectric conversion and fluid pumping with low-grade heat energy. As a basis of their performance enhancement, the effects of the structures and properties of the nanofluidic systems on the thermoelectric response (TER) and the thermoosmotic response (TOR) are yet to be explored. Methods: The simultaneous TER and…
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Hypothesis: Nanofluidic systems provide an emerging and efficient platform for thermoelectric conversion and fluid pumping with low-grade heat energy. As a basis of their performance enhancement, the effects of the structures and properties of the nanofluidic systems on the thermoelectric response (TER) and the thermoosmotic response (TOR) are yet to be explored. Methods: The simultaneous TER and TOR of electrolyte solutions in nanofluidic membrane pores on which an axial temperature gradient is exerted are investigated numerically and semi-analytically. A semi-analytical model is developed with the consideration of finite membrane thermal conductivity and the reservoir/entrance effect. Findings: The increase in the access resistance due to the nanopore-reservoir interfaces accounts for the decrease of short circuit current at the low concentration regime. The decrease in the thermal conductivity ratio can enhance the TER and TOR. The maximum power density occurring at the nanopore radius twice the Debye length ranges from several to dozens of mW K$^{-2}$ m$^{-2}$ and is an order of magnitude higher than typical thermo-supercapacitors. The surface charge polarity can heavily affect the sign and magnitude of the short-circuit current, the Seebeck coefficient, and the open-circuit thermoosmotic coefficient, but has less effect on the short-circuit thermoosmotic coefficient. Furthermore, the membrane thickness makes different impacts on TER and TOR for zero and finite membrane thermal conductivity.
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Submitted 12 September, 2023;
originally announced September 2023.
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Swift progress for robots over complex terrain
Authors:
Chen Li,
Feifei Qian
Abstract:
A four-legged robot has learned to run on sand at faster pace than humans jog on solid ground. With low energy use and few failures, this rapid robot shows the value of combining data-driven learning with accurate yet simple models.
A four-legged robot has learned to run on sand at faster pace than humans jog on solid ground. With low energy use and few failures, this rapid robot shows the value of combining data-driven learning with accurate yet simple models.
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Submitted 4 August, 2023;
originally announced August 2023.
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Graphene-assisted preparation of large-scale single crystal Ag(111) nanoparticle arrays
Authors:
Yibo Dong,
Yiyang Xie,
Liangchen Hu,
Chen Xu,
Weiling Guo,
Guanzhong Pan,
Qiuhua Wang,
Fengsong Qian,
Jie Sun
Abstract:
Surface plasmon resonance of metal nanostructures has broad application prospects in the fields of photocatalysis, optical sensing, biomarkers and surface-enhanced Raman scattering. This paper reports a graphene-assisted method for preparing large-scale single crystal Ag(111) nanoparticle arrays based on ion implantation technique. By surface periodic treatment and annealing of the implanted sampl…
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Surface plasmon resonance of metal nanostructures has broad application prospects in the fields of photocatalysis, optical sensing, biomarkers and surface-enhanced Raman scattering. This paper reports a graphene-assisted method for preparing large-scale single crystal Ag(111) nanoparticle arrays based on ion implantation technique. By surface periodic treatment and annealing of the implanted sample, regularly arranged Ag nanoparticles can be prepared on the sample surface. A new application for graphene is proposed, that is, as a perfect barrier layer to prevent metal atoms from evaporating or diffusing. All the Ag NPs show (111) crystal orientation. Besides, the Ag atoms are covered by graphene immediately when they precipitate from the substrate, which can prevent them from being oxidized. On the basis of this structure, as one of the applications of metal SPR, we measured the Raman enhancement effect, and found that the G peak of the Raman spectrum of graphene achieved about 20 times enhancement.
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Submitted 4 December, 2019;
originally announced December 2019.
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The dynamics of scattering in undulatory active collisions
Authors:
Jennifer M. Rieser,
Perrin E. Schiebel,
Arman Pazouki,
Feifei Qian,
Zachary Goddard,
Andrew Zangwill,
Dan Negrut,
Daniel I. Goldman
Abstract:
Natural and artificial self-propelled systems must manage environmental interactions during movement. Such interactions, which we refer to as active collisions, are fundamentally different from momentum-conserving interactions studied in classical physics, largely because the internal driving of the locomotor can lead to persistent contact with heterogeneities. Here, we experimentally and numerica…
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Natural and artificial self-propelled systems must manage environmental interactions during movement. Such interactions, which we refer to as active collisions, are fundamentally different from momentum-conserving interactions studied in classical physics, largely because the internal driving of the locomotor can lead to persistent contact with heterogeneities. Here, we experimentally and numerically study the effects of active collisions on a laterally-undulating sensory-deprived robophysical model, whose dynamics are applicable to self-propelled systems across length scales and environments. The robot moves via spatial undulation of body segments, with a nearly-linear center-of-geometry trajectory. Interactions with a single rigid post scatter the robot, and these deflections are proportional to the head-post contact duration. The distribution of scattering angles is smooth and strongly-peaked directly behind the post. Interactions with a single row of evenly-spaced posts (with inter-post spacing $d$) produce distributions reminiscent of far-field diffraction patterns: as $d$ decreases, distinct secondary peaks emerge as large deflections become more likely. Surprisingly, we find that the presence of multiple posts does not change the nature of individual collisions; instead, multi-modal scattering patterns arise from multiple posts altering the likelihood of individual collisions to occur. As $d$ decreases, collisions near the leading edges of the posts become more probable, and we find that these interactions are associated with larger deflections. Our results, which highlight the surprising dynamics that can occur during active collisions of self-propelled systems, can inform control principles for locomotors in complex terrain and facilitate design of task-capable active matter.
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Submitted 11 June, 2018; v1 submitted 30 November, 2017;
originally announced December 2017.
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A review on locomotion robophysics: the study of movement at the intersection of robotics, soft matter and dynamical systems
Authors:
Jeffrey Aguilar,
Tingnan Zhang,
Feifei Qian,
Mark Kingsbury,
Benjamin McInroe,
Nicole Mazouchova,
Chen Li,
Ryan Maladen,
Chaohui Gong,
Matt Travers,
Ross L. Hatton,
Howie Choset,
Paul B. Umbanhowar,
Daniel I. Goldman
Abstract:
In this review we argue for the creation of a physics of moving systems -- a locomotion "robophysics" -- which we define as the pursuit of the discovery of principles of self generated motion. Robophysics can provide an important intellectual complement to the discipline of robotics, largely the domain of researchers from engineering and computer science. The essential idea is that we must complem…
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In this review we argue for the creation of a physics of moving systems -- a locomotion "robophysics" -- which we define as the pursuit of the discovery of principles of self generated motion. Robophysics can provide an important intellectual complement to the discipline of robotics, largely the domain of researchers from engineering and computer science. The essential idea is that we must complement study of complex robots in complex situations with systematic study of simplified robophysical devices in controlled laboratory settings and simplified theoretical models. We must thus use the methods of physics to examine successful and failed locomotion in simplified (abstracted) devices using parameter space exploration, systematic control, and techniques from dynamical systems. Using examples from our and other's research, we will discuss how such robophysical studies have begun to aid engineers in the creation of devices that begin to achieve life-like locomotor abilities on and within complex environments, have inspired interesting physics questions in low dimensional dynamical systems, geometric mechanics and soft matter physics, and have been useful to develop models for biological locomotion in complex terrain. The rapidly decreasing cost of constructing sophisticated robot models with easy access to significant computational power bodes well for scientists and engineers to engage in a discipline which can readily integrate experiment, theory and computation.
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Submitted 12 February, 2016;
originally announced February 2016.
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Violation of Bell's Inequalities with Classical Shimony-Wolf States: Theory and Experiment
Authors:
X. F. Qian,
B. Little,
J. C. Howell,
J. H. Eberly
Abstract:
For many decades the word "entanglement" has been firmly attached to the world of quantum mechanics, as is the phrase "Bell violation". Here we introduce Shimony-Wolf fields, entirely classical non-deterministic states, as a basis for entanglement and Bell analyses. Such fields are well known in coherence optics and are open to test. We present experimental results showing that Shimony-Wolf states…
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For many decades the word "entanglement" has been firmly attached to the world of quantum mechanics, as is the phrase "Bell violation". Here we introduce Shimony-Wolf fields, entirely classical non-deterministic states, as a basis for entanglement and Bell analyses. Such fields are well known in coherence optics and are open to test. We present experimental results showing that Shimony-Wolf states exhibit strong classical Bell violation, in effect opening a way of examining a new sector of the boundary between quantum and classical physics.
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Submitted 12 June, 2014;
originally announced June 2014.
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Entangled states of light in classical polarization theory
Authors:
X. F. Qian,
J. H. Eberly
Abstract:
We formulate the classical polarization theory for light by using entanglement analysis. We demonstrate a route to a systematic and consistent measure of ordinary light polarization that extends automatically to a new understanding of the degree of polarization at a point, when a distinct beam direction is absent. We have drawn on recent work [Qian and Eberly, arXiv 1009.5622] dealing with the con…
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We formulate the classical polarization theory for light by using entanglement analysis. We demonstrate a route to a systematic and consistent measure of ordinary light polarization that extends automatically to a new understanding of the degree of polarization at a point, when a distinct beam direction is absent. We have drawn on recent work [Qian and Eberly, arXiv 1009.5622] dealing with the conservation of quantum information.
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Submitted 31 October, 2011; v1 submitted 2 November, 2010;
originally announced November 2010.