1
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Fedorov A, Kumar NP, Le DT, Navarathna R, Pakkiam P, Stace TM. Nonreciprocity and Circulation in a Passive Josephson-Junction Ring. Phys Rev Lett 2024; 132:097001. [PMID: 38489656 DOI: 10.1103/physrevlett.132.097001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 01/30/2024] [Accepted: 02/02/2024] [Indexed: 03/17/2024]
Abstract
Building large-scale superconducting quantum circuits will require miniaturization and integration of supporting devices including microwave circulators, which are currently bulky, stand-alone components. Here, we report the measurement of microwave scattering from a ring of Josephson junctions, with dc-only control fields. We detect the effect of quasiparticle tunneling, and dynamically classify the system at its operating design point into different quasiparticle sectors. We optimize the device within one of the quasiparticle sectors, where we observe an unambiguous signature of nonreciprocal 3-port scattering within that sector. This enables operation as a circulator, and at the optimal circulation point, we observe on-resonance insertion loss of 2 dB, isolation of 14 dB, power reflectance of -11 dB, and a bandwidth of 200 MHz, averaged over the 3 input ports.
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Affiliation(s)
- Arkady Fedorov
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - N Pradeep Kumar
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Dat Thanh Le
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Rohit Navarathna
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Prasanna Pakkiam
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
| | - Thomas M Stace
- Analog Quantum Circuits Pty. Ltd., Brisbane, Australia and School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia
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2
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Navarathna R, Le DT, Hamann AR, Nguyen HD, Stace TM, Fedorov A. Passive Superconducting Circulator on a Chip. Phys Rev Lett 2023; 130:037001. [PMID: 36763376 DOI: 10.1103/physrevlett.130.037001] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 01/03/2023] [Indexed: 06/18/2023]
Abstract
An on-chip microwave circulator that is compatible with superconducting devices is a key element for scale up of superconducting circuits. Previous approaches to integrating circulators on chip involve either external driving that requires extra microwave lines or a strong magnetic field that would compromise superconductivity. Here we report the first proof-of-principle realization of a passive on-chip circulator that is made from a superconducting loop interrupted by three notionally identical Josephson junctions and is tuned with only dc control fields. Our experimental results show evidence for nonreciprocal scattering, and excellent agreement with theoretical simulations. We also present a detailed analysis of quasiparticle tunneling in our device using a hidden Markov model. By reducing the junction asymmetry and utilizing the known methods of protection from quasiparticles, we anticipate that Josephson-loop circulator will become ubiquitous in superconducting circuits.
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Affiliation(s)
- Rohit Navarathna
- ARC Centre for Engineered Quantum System, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
| | - Dat Thanh Le
- ARC Centre for Engineered Quantum System, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
| | - Andrés Rosario Hamann
- ARC Centre for Engineered Quantum System, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
| | - Hien Duy Nguyen
- School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
| | - Thomas M Stace
- ARC Centre for Engineered Quantum System, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
- Analog Quantum Circuits Pty. Ltd., Brisbane QLD 4072, Australia
| | - Arkady Fedorov
- ARC Centre for Engineered Quantum System, School of Mathematics and Physics, University of Queensland, Brisbane QLD 4072, Australia
- Analog Quantum Circuits Pty. Ltd., Brisbane QLD 4072, Australia
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3
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Abstract
We introduce tensor-network stabilizer codes which come with a natural tensor-network decoder. These codes can correspond to any geometry, but, as a special case, we generalize holographic codes beyond those constructed from perfect or block-perfect isometries, and we give an example that corresponds to neither. Using the tensor-network decoder, we find a threshold of 18.8% for this code under depolarizing noise. We show that, for holographic codes, the exact tensor-network decoder (with no bond-dimension truncation) has polynomial complexity in the number of physical qubits, even for locally correlated noise, making this the first efficient decoder for holographic codes against Pauli noise and, also, a rare example of a decoder that is both efficient and exact.
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Affiliation(s)
- Terry Farrelly
- ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Robert J Harris
- ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Nathan A McMahon
- ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
- Department of Physics, Friedrich-Alexander University Erlangen-Nürnberg (FAU), D-91058 Erlangen, Germany
| | - Thomas M Stace
- ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St. Lucia, Queensland 4072, Australia
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4
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Birchall PM, Allen EJ, Stace TM, O'Brien JL, Matthews JCF, Cable H. Quantum Optical Metrology of Correlated Phase and Loss. Phys Rev Lett 2020; 124:140501. [PMID: 32338951 DOI: 10.1103/physrevlett.124.140501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 03/16/2020] [Indexed: 06/11/2023]
Abstract
Optical absorption measurements characterize a wide variety of systems from atomic gases to in vivo diagnostics of living organisms. Here we study the potential of nonclassical techniques to reduce statistical noise below the shot-noise limit in absorption measurements with concomitant phase shifts imparted by a sample. We consider both cases where there is a known relationship between absorption and a phase shift, and where this relationship is unknown. For each case we derive the fundamental limit and provide a practical strategy to reduce statistical noise. Furthermore, we find an intuitive correspondence between measurements of absorption and of lossy phase shifts, which both show the same analytical form for precision enhancement for bright states. Our results demonstrate that nonclassical techniques can aid real-world tasks with present-day laboratory techniques.
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Affiliation(s)
- Patrick M Birchall
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol BS8 1FD, United Kingdom
| | - Euan J Allen
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol BS8 1FD, United Kingdom
- Quantum Engineering Centre for Doctoral Training, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Tyndall Avenue, Bristol BS8 1FD, United Kingdom
| | - Thomas M Stace
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - Jeremy L O'Brien
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol BS8 1FD, United Kingdom
- School of Physics, University of Western Australia, Perth, 6009, Australia
| | - Jonathan C F Matthews
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol BS8 1FD, United Kingdom
| | - Hugo Cable
- Quantum Engineering Technology Labs, H. H. Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol BS8 1FD, United Kingdom
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5
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Abstract
Spontaneous wave-function collapse models, like continuous spontaneous localization, are designed to suppress macroscopic superpositions while preserving microscopic quantum phenomena. An observable consequence of collapse models is spontaneous heating of massive objects. We calculate the collapse-induced heating rate of astrophysical objects, and the corresponding equilibrium temperature. We apply these results to neutron stars, the densest phase of baryonic matter in the Universe. Stronger collapse model parameters imply greater heating, allowing us to derive competitive bounds on model parameters using neutron star observational data, and to propose speculative bounds based on the capabilities of current and future astronomical surveys.
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Affiliation(s)
- Antoine Tilloy
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany
| | - Thomas M Stace
- ARC Centre for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
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6
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Rosario Hamann A, Müller C, Jerger M, Zanner M, Combes J, Pletyukhov M, Weides M, Stace TM, Fedorov A. Nonreciprocity Realized with Quantum Nonlinearity. Phys Rev Lett 2018; 121:123601. [PMID: 30296135 DOI: 10.1103/physrevlett.121.123601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Indexed: 06/08/2023]
Abstract
Nonreciprocal devices are a key element for signal routing and noise isolation. Rapid development of quantum technologies has boosted the demand for a new generation of miniaturized and low-loss nonreciprocal components. Here, we use a pair of tunable superconducting artificial atoms in a 1D waveguide to experimentally realize a minimal passive nonreciprocal device. Taking advantage of the quantum nonlinear behavior of artificial atoms, we achieve nonreciprocal transmission through the waveguide in a wide range of powers. Our results are consistent with theoretical modeling showing that nonreciprocity is associated with the population of the two-qubit nonlocal entangled quasidark state, which responds asymmetrically to incident fields from opposing directions. Our experiment highlights the role of quantum correlations in enabling nonreciprocal behavior and opens a path to building passive quantum nonreciprocal devices without magnetic fields.
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Affiliation(s)
- Andrés Rosario Hamann
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - Clemens Müller
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Markus Jerger
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - Maximilian Zanner
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - Joshua Combes
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - Mikhail Pletyukhov
- Institute for Theory of Statistical Physics, RWTH Aachen University, 52056 Aachen, Germany
| | - Martin Weides
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
- School of Engineering, Electronics & Nanoscale Engineering Division, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Thomas M Stace
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - Arkady Fedorov
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Saint Lucia, Queensland 4072, Australia
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7
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Müller C, Guan S, Vogt N, Cole JH, Stace TM. Passive On-Chip Superconducting Circulator Using a Ring of Tunnel Junctions. Phys Rev Lett 2018; 120:213602. [PMID: 29883153 DOI: 10.1103/physrevlett.120.213602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Indexed: 06/08/2023]
Abstract
We present the design of a passive, on-chip microwave circulator based on a ring of superconducting tunnel junctions. We investigate two distinct physical realizations, based on Josephson junctions (JJs) or quantum phase slip elements (QPS), with microwave ports coupled either capacitively (JJ) or inductively (QPS) to the ring structure. A constant bias applied to the center of the ring provides an effective symmetry breaking field, and no microwave or rf bias is required. We show that this design offers high isolation, robustness against fabrication imperfections and bias fluctuations, and a bandwidth in excess of 500 MHz for realistic device parameters.
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Affiliation(s)
- Clemens Müller
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
- Institute for Theoretical Physics, ETH Zürich, 8093 Zürich, Switzerland
| | - Shengwei Guan
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Nicolas Vogt
- Chemical and Quantum Physics, School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | - Jared H Cole
- Chemical and Quantum Physics, School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | - Thomas M Stace
- ARC Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4072, Australia
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8
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Brennen GK, Pupillo G, Rico E, Stace TM, Vodola D. Loops and Strings in a Superconducting Lattice Gauge Simulator. Phys Rev Lett 2016; 117:240504. [PMID: 28009201 DOI: 10.1103/physrevlett.117.240504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Indexed: 06/06/2023]
Abstract
We propose an architecture for an analog quantum simulator of electromagnetism in 2+1 dimensions, based on an array of superconducting fluxonium devices. The encoding is in the integer (spin-1) representation of the quantum link model formulation of compact U(1) lattice gauge theory. We show how to engineer Gauss' law via an ancilla mediated gadget construction, and how to tune between the strongly coupled and intermediately coupled regimes. The witnesses to the existence of the predicted confining phase of the model are provided by nonlocal order parameters from Wilson loops and disorder parameters from 't Hooft strings. We show how to construct such operators in this model and how to measure them nondestructively via dispersive coupling of the fluxonium islands to a microwave cavity mode. Numerical evidence is found for the existence of the confined phase in the ground state of the simulation Hamiltonian on a ladder geometry.
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Affiliation(s)
- G K Brennen
- Centre for Engineered Quantum Systems, Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia
| | - G Pupillo
- icFRC, IPCMS (UMR 7504) and ISIS (UMR 7006), Universite de Strasbourg and CNRS,67000 Strasbourg, France
| | - E Rico
- Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, E-48080 Bilbao, Spain
- IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, E-48013 Bilbao, Spain
| | - T M Stace
- Center for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - D Vodola
- icFRC, IPCMS (UMR 7504) and ISIS (UMR 7006), Universite de Strasbourg and CNRS,67000 Strasbourg, France
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9
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Abstract
We show how to construct a large class of quantum error-correcting codes, known as Calderbank-Steane-Shor codes, from highly entangled cluster states. This becomes a primitive in a protocol that foliates a series of such cluster states into a much larger cluster state, implementing foliated quantum error correction. We exemplify this construction with several familiar quantum error-correction codes and propose a generic method for decoding foliated codes. We numerically evaluate the error-correction performance of a family of finite-rate Calderbank-Steane-Shor codes known as turbo codes, finding that they perform well over moderate depth foliations. Foliated codes have applications for quantum repeaters and fault-tolerant measurement-based quantum computation.
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Affiliation(s)
- A Bolt
- ARC Centre for Engineered Quantum System, Department of Physics, University of Queensland, Brisbane, Queensland 4072, Australia
| | - G Duclos-Cianci
- Département de Physique, Université de Sherbrooke, Québec J1K 2R1, Canada
| | - D Poulin
- Département de Physique, Université de Sherbrooke, Québec J1K 2R1, Canada
| | - T M Stace
- ARC Centre for Engineered Quantum System, Department of Physics, University of Queensland, Brisbane, Queensland 4072, Australia
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10
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Sia PI, Luiten AN, Stace TM, Wood JPM, Casson RJ. Quantum biology of the retina. Clin Exp Ophthalmol 2014; 42:582-9. [DOI: 10.1111/ceo.12373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 06/10/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Paul Ikgan Sia
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
| | - André N Luiten
- Institute for Photonics and Advanced Sensing (IPAS); School of Chemistry and Physics; University of Adelaide; Adelaide South Australia Australia
| | - Thomas M Stace
- School of Mathematics and Physics; University of Queensland; Brisbane Queensland Australia
| | - John PM Wood
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
| | - Robert J Casson
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
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11
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Weng W, Anstie JD, Stace TM, Campbell G, Baynes FN, Luiten AN. Nano-Kelvin thermometry and temperature control: beyond the thermal noise limit. Phys Rev Lett 2014; 112:160801. [PMID: 24815630 DOI: 10.1103/physrevlett.112.160801] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Indexed: 06/03/2023]
Abstract
We demonstrate thermometry with a resolution of 80 nK/Hz using an isotropic crystalline whispering-gallery mode resonator based on a dichroic dual-mode technique. We simultaneously excite two modes that have a mode frequency ratio that is very close to two (±0.3 ppm). The wavelength and temperature dependence of the refractive index means that the frequency difference between these modes is an ultrasensitive proxy of the resonator temperature. This approach to temperature sensing automatically suppresses sensitivity to thermal expansion and vibrationally induced changes of the resonator. We also demonstrate active suppression of temperature fluctuations in the resonator by controlling the intensity of the driving laser. The residual temperature fluctuations are shown to be below the limits set by fundamental thermodynamic fluctuations of the resonator material.
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Affiliation(s)
- Wenle Weng
- School of Physics, University of Western Australia, Western Australia 6009, Australia and Institute for Photonics and Advanced Sensing and School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia
| | - James D Anstie
- School of Physics, University of Western Australia, Western Australia 6009, Australia and Institute for Photonics and Advanced Sensing and School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia
| | - Thomas M Stace
- School of Mathematics and Physics, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Geoff Campbell
- Department of Quantum Science, Australian National University, Australian Capital Territory 0200, Australia
| | - Fred N Baynes
- School of Physics, University of Western Australia, Western Australia 6009, Australia
| | - Andre N Luiten
- School of Physics, University of Western Australia, Western Australia 6009, Australia and Institute for Photonics and Advanced Sensing and School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia
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12
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Sathyamoorthy SR, Tornberg L, Kockum AF, Baragiola BQ, Combes J, Wilson CM, Stace TM, Johansson G. Quantum nondemolition detection of a propagating microwave photon. Phys Rev Lett 2014; 112:093601. [PMID: 24655250 DOI: 10.1103/physrevlett.112.093601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Indexed: 05/27/2023]
Abstract
The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realizing such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon interactions in a waveguide have recently been demonstrated. Here we show how this type of interaction can be used to realize a quantum nondemolition measurement of a single propagating microwave photon. The scheme we propose uses a chain of solid-state three-level systems (transmons) cascaded through circulators which suppress photon backscattering. Our theoretical analysis shows that microwave-photon detection with fidelity around 90% can be realized with existing technologies.
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Affiliation(s)
- Sankar R Sathyamoorthy
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-41296 Gothenburg, Sweden
| | - L Tornberg
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-41296 Gothenburg, Sweden
| | - Anton F Kockum
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-41296 Gothenburg, Sweden
| | - Ben Q Baragiola
- Center for Quantum Information and Control, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
| | - Joshua Combes
- Center for Quantum Information and Control, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
| | - C M Wilson
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-41296 Gothenburg, Sweden and Institute for Quantum Computing and Electrical and Computer Engineering Department, University of Waterloo, Waterloo N2 L 3G1, Canada
| | - Thomas M Stace
- Centre for Engineered Quantum Systems, School of Physical Sciences, University of Queensland, Saint Lucia, Queensland 4072, Australia
| | - G Johansson
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, S-41296 Gothenburg, Sweden
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13
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Abstract
We derive dynamical equations for a driven, dissipative quantum system in which the environment-induced relaxation rate is comparable to the Rabi frequency, avoiding assumptions on the frequency dependence of the environmental coupling. When the environmental coupling varies significantly on the scale of the Rabi frequency, secular or rotating wave approximations break down. We avoid these approximations, yielding dynamical steady states which account for the interaction between driven quantum dots and their phonon environment. The theory, which is motivated by recent experimental observations, qualitatively and quantitatively describes the transition from asymmetric unsaturated resonances at weak driving to population inversion at strong driving.
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Affiliation(s)
- T M Stace
- ARC Centre for Engineered Quantum Systems, University of Queensland, Brisbane 4072, Australia
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14
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Harris GI, McAuslan DL, Stace TM, Doherty AC, Bowen WP. Minimum requirements for feedback enhanced force sensing. Phys Rev Lett 2013; 111:103603. [PMID: 25166666 DOI: 10.1103/physrevlett.111.103603] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Indexed: 06/03/2023]
Abstract
The problem of estimating an unknown force driving a linear oscillator is revisited. When using linear measurement, feedback is often cited as a mechanism to enhance bandwidth, sensitivity or resolution. We show that as long as the oscillator dynamics are known, there exists a real-time estimation strategy that reproduces the same measurement record as any arbitrary feedback protocol. Consequently some form of nonlinearity is required to gain any advantage beyond estimation alone. This result holds true in both quantum and classical systems, with nonstationary forces and feedback, and in the general case of non-Gaussian and correlated noise. Recently, feedback enhanced incoherent force resolution has been demonstrated [E. Gavartin, P. Verlot, and T. J. Kippenberg, Nat. Nano. 7, 509 (2012)], with the enhancement attributed to a feedback induced modification of the mechanical susceptibility. As a proof-of-principle, we experimentally reproduce this result through straightforward filtering.
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Affiliation(s)
- Glen I Harris
- Centre for Engineered Quantum Systems, University of Queensland, St. Lucia, Queensland 4072, Australia
| | - David L McAuslan
- Centre for Engineered Quantum Systems, University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Thomas M Stace
- Centre for Engineered Quantum Systems, University of Queensland, St. Lucia, Queensland 4072, Australia
| | - Andrew C Doherty
- Centre for Engineered Quantum Systems, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Warwick P Bowen
- Centre for Engineered Quantum Systems, University of Queensland, St. Lucia, Queensland 4072, Australia
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15
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Hoi IC, Kockum AF, Palomaki T, Stace TM, Fan B, Tornberg L, Sathyamoorthy SR, Johansson G, Delsing P, Wilson CM. Giant cross-Kerr effect for propagating microwaves induced by an artificial atom. Phys Rev Lett 2013; 111:053601. [PMID: 23952397 DOI: 10.1103/physrevlett.111.053601] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 03/21/2013] [Indexed: 06/02/2023]
Abstract
We investigate the effective interaction between two microwave fields, mediated by a transmon-type superconducting artificial atom which is strongly coupled to a coplanar transmission line. The interaction between the fields and atom produces an effective cross-Kerr coupling. We demonstrate average cross-Kerr phase shifts of up to 20 degrees per photon with both coherent microwave fields at the single-photon level. Our results provide an important step toward quantum applications with propagating microwave photons.
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Affiliation(s)
- Io-Chun Hoi
- Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
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16
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Fan B, Kockum AF, Combes J, Johansson G, Hoi IC, Wilson CM, Delsing P, Milburn GJ, Stace TM. Breakdown of the cross-Kerr scheme for photon counting. Phys Rev Lett 2013; 110:053601. [PMID: 23414018 DOI: 10.1103/physrevlett.110.053601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Indexed: 06/01/2023]
Abstract
We show, in the context of single-photon detection, that an atomic three-level model for a transmon in a transmission line does not support the predictions of the nonlinear polarizability model known as the cross-Kerr effect. We show that the induced displacement of a probe in the presence or absence of a single photon in the signal field, cannot be resolved above the quantum noise in the probe. This strongly suggests that cross-Kerr media are not suitable for photon counting or related single-photon applications. Our results are presented in the context of a transmon in a one-dimensional microwave waveguide, but the conclusions also apply to optical systems.
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Affiliation(s)
- Bixuan Fan
- Center for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
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17
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Lurie A, Light PS, Anstie J, Stace TM, Abbott PC, Benabid F, Luiten AN. Saturation spectroscopy of iodine in hollow-core optical fiber. Opt Express 2012; 20:11906-11917. [PMID: 22714176 DOI: 10.1364/oe.20.011906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present high-resolution spectroscopy of I(2) vapor that is loaded and trapped within the core of a hollow-core photonic crystal fiber (HC-PCF). We compare the observed spectroscopic features to those observed in a conventional iodine cell and show that the saturation characteristics differ significantly. Despite the confined geometry it was still possible to obtain sub-Doppler features with a spectral width of ~6 MHz with very high contrast. We provide a simple theory which closely reproduces all the key observations of the experiment.
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Affiliation(s)
- Anna Lurie
- School of Physics, The University of Western Australia, Crawley, Western Australia 6009, Australia
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18
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Lurie A, Baynes FN, Anstie JD, Light PS, Benabid F, Stace TM, Luiten AN. High-performance iodine fiber frequency standard. Opt Lett 2011; 36:4776-4778. [PMID: 22179880 DOI: 10.1364/ol.36.004776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have constructed a compact and robust optical frequency standard based around iodine vapor loaded into the core of a hollow-core photonic crystal fiber (HC-PCF). A 532 nm laser was frequency locked to one hyperfine component of the R(56) 32-0 (127)I(2) transition using modulation transfer spectroscopy. The stabilized laser demonstrated a frequency stability of 2.3×10(-12) at 1 s, almost an order of magnitude better than previously reported for a laser stabilized to a gas-filled HC-PCF. This limit is set by the shot noise in the detection system. We present a discussion of the current limitations to the performance and a route to improve the performance by more than an order of magnitude.
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Affiliation(s)
- Anna Lurie
- Frequency Standards and Metrology Group, School of Physics, The University of Western Australia, Perth, Western Australia.
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19
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Abstract
Many applications in optical quantum information processing benefit from careful spectral shaping of single-photon wave-packets. In this paper we tailor the joint spectral wave-function of photons created in parametric downconversion by engineering the nonlinearity profile of a poled crystal. We designed a crystal with an approximately Gaussian nonlinearity profile and confirmed successful wave-packet shaping by two-photon interference experiments. We numerically show how our method can be applied for attaining one of the currently most important goals of single-photon quantum optics, the creation of pure single photons without spectral correlations.
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Affiliation(s)
- Agata M Brańczyk
- Center for Quantum Computer Technology, Department of Physics, The University of Queensland, QLD, Australia
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20
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Li Y, Barrett SD, Stace TM, Benjamin SC. Fault tolerant quantum computation with nondeterministic gates. Phys Rev Lett 2010; 105:250502. [PMID: 21231569 DOI: 10.1103/physrevlett.105.250502] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Indexed: 05/30/2023]
Abstract
In certain approaches to quantum computing the operations between qubits are nondeterministic and likely to fail. For example, a distributed quantum processor would achieve scalability by networking together many small components; operations between components should be assumed to be failure prone. In the ultimate limit of this architecture each component contains only one qubit. Here we derive thresholds for fault-tolerant quantum computation under this extreme paradigm. We find that computation is supported for remarkably high failure rates (exceeding 90%) providing that failures are heralded; meanwhile the rate of unknown errors should not exceed 2 in 10(4) operations.
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Affiliation(s)
- Ying Li
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore
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21
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Abstract
Many proposals for fault tolerant quantum computation (FTQC) suffer detectable loss processes. Here we show that topological FTQC schemes, which are known to have high error thresholds, are also extremely robust against losses. We demonstrate that these schemes tolerate loss rates up to 24.9%, determined by bond percolation on a cubic lattice. Our numerical results show that these schemes retain good performance when loss and computational errors are simultaneously present.
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Affiliation(s)
- Sean D Barrett
- Centre for Quantum Science and Technology, Macquarie University, New South Wales 2109, Australia.
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22
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Abstract
Many proposals for quantum information processing are subject to detectable loss errors. In this Letter, we show that topological error correcting codes, which protect against computational errors, are also extremely robust against losses. We present analytical results showing that the maximum tolerable loss rate is 50%, which is determined by the square-lattice bond percolation threshold. This saturates the bound set by the no-cloning theorem. Our numerical results support this and show a graceful trade-off between tolerable thresholds for computational and loss errors.
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Affiliation(s)
- Thomas M Stace
- School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia.
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23
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Kolli A, Lovett BW, Benjamin SC, Stace TM. All-optical measurement-based quantum-information processing in quantum dots. Phys Rev Lett 2006; 97:250504. [PMID: 17280337 DOI: 10.1103/physrevlett.97.250504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Indexed: 05/13/2023]
Abstract
Parity measurements on qubits can generate the entanglement resource necessary for scalable quantum computation. Here we describe a method for fast optical parity measurements on electron spin qubits within coupled quantum dots. The measurement scheme, which can be realized with existing technology, consists of the optical excitation of excitonic states followed by monitored relaxation. Conditional on the observation of a photon, the system is projected into the odd/even-parity subspaces. Our model incorporates all the primary sources of error, including detector inefficiency, effects of spatial separation and nonresonance of the dots, and also unwanted excitations. Through an analytical treatment we establish that the scheme is robust to such effects. Two applications are presented: a realization of a controlled-NOT gate, and a technique for growing large scale graph states.
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Affiliation(s)
- Avinash Kolli
- Department of Materials, Oxford University, Oxford OX1 3PH, United Kingdom.
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24
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Abstract
We analyze the dynamics of a continuously observed, damped, microwave-driven solid state charge qubit, consisting of a single electron in a double well potential. The microwave field induces transitions between the qubit eigenstates, which have a profound effect on the detector output current. Useful information about the qubit dynamics, such as dephasing and relaxation rates, and the Rabi frequency, can be extracted from the detector conductance and output noise power spectrum. We also propose a technique for single-shot electron spin readout, for spin based quantum information processing, which has a number of practical advantages over existing schemes.
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Affiliation(s)
- S D Barrett
- Hewlett-Packard Laboratories, Filton Road, Stoke Gifford, Bristol BS34 8QZ, United Kingdom.
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Stace TM, Doherty AC, Barrett SD. Population inversion of a driven two-level system in a structureless bath. Phys Rev Lett 2005; 95:106801. [PMID: 16196950 DOI: 10.1103/physrevlett.95.106801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Indexed: 05/04/2023]
Abstract
We derive a master equation for a driven double quantum dot damped by an unstructured phonon bath, and calculate the spectral density. We find that bath-mediated photon absorption is important at relatively strong driving, and may even dominate the dynamics, inducing population inversion of the double-dot system. This phenomenon is consistent with recent experimental observations.
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Stace TM, Barnes CHW, Milburn GJ. Mesoscopic one-way channels for quantum state transfer via the quantum Hall effect. Phys Rev Lett 2004; 93:126804. [PMID: 15447298 DOI: 10.1103/physrevlett.93.126804] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Indexed: 05/24/2023]
Abstract
We show that the one-way channel formalism of quantum optics has a physical realization in electronic systems. In particular, we show that magnetic edge states form unidirectional quantum channels capable of coherently transporting electronic quantum information. Using the equivalence between one-way photonic channels and magnetic edge states, we adapt a proposal for quantum state transfer to mesoscopic systems using edge states as a quantum channel, and show that it is feasible with reasonable experimental parameters. We discuss how this protocol may be used to transfer information encoded in number, charge, or spin states of quantum dots, so it may prove useful for transferring quantum information between parts of a solid-state quantum computer.
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Affiliation(s)
- T M Stace
- Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom.
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Stace TM, Barrett SD. Continuous quantum measurement: inelastic tunneling and lack of current oscillations. Phys Rev Lett 2004; 92:136802. [PMID: 15089636 DOI: 10.1103/physrevlett.92.136802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Indexed: 05/24/2023]
Abstract
We study the dynamics of a charge qubit, consisting of a single electron in a double well potential coupled to a point-contact (PC) electrometer, using the quantum trajectories formalism. Contrary to previous predictions, we show formally that, in the sub-Zeno limit, coherent oscillations in the detector output are suppressed, and the dynamics is dominated by inelastic processes in the PC. Furthermore, these reduce the detector efficiency and induce relaxation even when the source-drain bias is zero. This is of practical significance since it means the detector will act as a source of decoherence. Finally, we show that the sub-Zeno dynamics is divided into two regimes: low and high bias in which the PC current power spectra show markedly different behavior.
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Affiliation(s)
- T M Stace
- Cavendish Laboratory and DAMTP, University of Cambridge, Cambridge, United Kingdom.
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Abstract
A mechano-electrochemical theory of the surface glycocalyx on capillary endothelial cells is presented that models the structure as a mixture of electrostatically charged macromolecules hydrated in an electrolytic fluid. Disturbances arising from mechanical deformation are introduced as perturbations away from a nearly electroneutral equilibrium environment. Under mechanical compression of the layer, such as might occur on the passing of stiff leukocytes through capillaries, the model predicts that gradients in the electrochemical potential of the compressed layer cause a redistribution of mobile ions within the glycocalyx and a rehydration and restoration of the layer to its equilibrium dimensions. Because of the large deformations of the glycocalyx arising from passing leukocytes, nonlinear kinematics associated with finite deformations of the layer are accounted for in the theory. A pseudo-equilibrium approximation is invoked for the transport of the mobile ions that reduces the system of coupled nonlinear integro-differential equations to a single nonlinear partial differential equation that is solved numerically for the compression and recovery of the glycocalyx using a finite difference method on a fixed grid. A linearized model for small strains is also obtained as verification of the finite difference solution. Results of the asymptotic analysis agree well with the nonlinear solution in the limit of small deformations of the layer. Using existing experimental and theoretical estimates of glycocalyx properties, the glycocalyx fixed-charge density is estimated from the analysis to be approximately 1 mEq/l, i.e., we estimate that there exists approximately one fixed charge on the glycocalyx for every 100 ions in blood. Such a charge density would result in a voltage differential between the undeformed glycocalyx and the capillary lumen of approximately 0.1 mV. In addition to providing insight into the mechano-electrochemical dynamics of the layer under deformation, the model suggests several methods for obtaining improved estimates of the glycocalyx fixed-charge density and permeability in vivo.
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Affiliation(s)
- Edward R Damiano
- Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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Abstract
An electrochemical theory of the glycocalyx surface layer on capillary endothelial cells is developed as a model to study the electrochemical dynamics of anionic molecular transport within capillaries. Combining a constitutive relationship for electrochemical transport, derived from Fick's and Ohm's laws, with the conservation of mass and Gauss's law from electrostatics, a system of three nonlinear, coupled, second-order, partial, integro-differential equations is obtained for the concentrations of the diffusing anionic molecules and the cations and anions in the blood. With the exception of small departures from electroneutrality that arise locally near the apical region of the glycocalyx, the model assumes that cations in the blood counterbalance the fixed negative charges bound to the macromolecular matrix of the glycocalyx in equilibrium. In the presence of anionic molecular tracers injected into the capillary lumen, the model predicts the size- and charge-dependent electrophoretic mobility of ions and tracers within the layer. In particular, the model predicts that anionic molecules are excluded from the glycocalyx at equilibrium and that the extent of this exclusion, which increases with increasing tracer and/or glycocalyx electronegativity, is a fundamental determinant of anionic molecular transport through the layer. The model equations were integrated numerically using a Crank-Nicolson finite-difference scheme and Newton-Raphson iteration. When the concentration of the anionic molecular tracer is small compared with the concentration of ions in the blood, a linearized version of the model can be obtained and solved as an eigenvalue problem. The results of the linear and nonlinear models were found to be in good agreement for this physiologically important case. Furthermore, if the fixed-charge density of the glycocalyx is of the order of the concentration of ions in the blood, or larger, or if the magnitude of the anionic molecular valence is large, a closed-form asymptotic solution for the diffusion time can be obtained from the eigenvalue problem that compares favorably with the numerical solution. In either case, if leakage of anionic molecules out of the capillary occurs, diffusion time is seen to vary exponentially with anionic valence and in inverse proportion to the steady-state anionic tracer concentration in the layer relative to the lumen. These findings suggest several methods for obtaining an estimate of the glycocalyx fixed-charge density in vivo.
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Affiliation(s)
- T M Stace
- Department of Physics, University of Western Australia, Perth, Australia
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