Publications

The most updated list of my publications can be found on my Google Scholar profile

Long-distance photon-mediated and short-distance entangling gates in three-qubit quantum dot spin systems

(Editor's suggestion)

NM Estakhri, A Warren, Sophia E Economou, E Barnes

Physical Review Research 6, 043029 (2024)

Quantum thermalization and Floquet engineering in a spin ensemble with a clock transition

Mi Lei, Rikuto Fukumori, Chun-Ju Wu, Edwin Barnes, Sophia E Economou, Joonhee Choi, Andrei Faraon

arXiv:2408.00252

Adaptive Quantum Generative Training using an Unbounded Loss Function

Kyle Sherbert, Jim Furches, Karunya Shirali, Sophia E Economou, Carlos Ortiz Marrero

arXiv:2408.00218

Optimization complexity and resource minimization of emitter-based photonic graph state generation protocols

Evangelia Takou, Edwin Barnes, Sophi E Economou

arXiv:2407.15777

Minimal evolution times for fast, pulse-based state preparation in silicon spin qubits

Christopher K Long, Nicholas J Mayhall, Sophia E Economou, Edwin Barnes, Crispin HW Barnes, Frederico Martins, David RM Arvidsson-Shukur, Normann Mertig

arXiv:2406.10913

Parameterization and optimizability of pulse-level VQEs

Kyle M Sherbert, Hisham Amer, Sophia E Economou, Edwin Barnes, Nicholas J Mayhall

arXiv:2405.15166

High-throughput assessment of defect-nuclear spin register controllability for quantum memory applications

Filippos Dakis, Evangelia Takou, Edwin Barnes, Sophia E Economou

arXiv:2405.10778

Deterministic generation of qudit photonic graph states from quantum emitters

Zahra Raissi, Edwin Barnes, Sophia E Economou

PRX Quantum 5, 020346 (2024)

Generation of genuine all-way entanglement in defect-nuclear spin systems through dynamical decoupling sequences

Evangelia Takou, Edwin Barnes, Sophia E Economou

Quantum 8, 1304 (2024)

TETRIS-ADAPT-VQE: An adaptive algorithm that yields shallower, denser circuit Ansätze

Panagiotis G. Anastasiou, Yanzhu Chen, Nicholas J. Mayhall, Edwin Barnes, and Sophia E. Economou

Physical Review Research 6, 013254 (2024)

Scaling adaptive quantum simulation algorithms via operator pool tiling

John S Van Dyke, Karunya Shirali, GS Barron, Nicholas J Mayhall, Edwin Barnes, Sophia E Economou

Physical Review Research 6, L012030 (2024)

Reducing measurement costs by recycling the Hessian in adaptive variational quantum algorithms

Mafalda Ramôa, Luis Paulo Santos, Nicholas J Mayhall, Edwin Barnes, Sophia E Economou

arXiv:2401.05172

Linear optical logical Bell state measurements with optimal loss-tolerance threshold

P Hilaire, Y Castor, E Barnes, SE Economou, F Grosshans

PRX Quantum 4, 040322 (2023)

ADAPT-QAOA with a classically inspired initial state

Vishvesha K Sridhar, Y Chen, B Gard, E Barnes, Sophia E Economou

arXiv:2310.09694

Quantum repeaters: From quantum networks to the quantum internet

Koji Azuma, Sophia E Economou, David Elkouss, Paul Hilaire, Liang Jiang, Hoi-Kwong Lo, Ilan Tzitrin

Reviews of Modern Physics 95, 045006 (2023)

Randomized adaptive quantum state preparation

Alicia B Magann, Sophia E Economou, Christian Arenz

Physical Review Research 5, 033227 (2024)

Protocol for nearly deterministic parity projection on two photonic qubits

C Liu, R Frantzeskakis, Sophia E Economou, Edwin Barnes

arXiv:2308.09035

Time-crystalline behavior in central-spin models with Heisenberg interactions

R Frantzeskakis, J Van Dyke, L Zaporski, DA Gangloff, C Le Gall, Mete Atatüre, Sophia E. Economou, and Edwin Barnes

Physical Review B 108, 075302 (2023)

High-rate entanglement between a semiconductor spin and indistinguishable photons

N. Coste, D. A. Fioretto, N. Belabas, S. C. Wein, P. Hilaire, R. Frantzeskakis, M. Gundin, B. Goes, N. Somaschi, M. Morassi, A. Lemaître, I. Sagnes, A. Harouri, Sophia E. Economou, A. Auffeves, O. Krebs, L. Lanco, P. Senellart

Nature Photonics 17, 582 (2023)

Avoiding leakage and errors caused by unwanted transitions in lambda systems

A Vezvaee, E Takou, P Hilaire, MF Doty, Sophia E Economou

PRX Quantum 4, 030312 (2023)

Adaptive variational algorithms for quantum Gibbs state preparation

A Warren, L Zhu, NJ Mayhall, E Barnes, SE Economou

arXiv:2203.12757

Multipartite electron-nuclear gates in defect systems through dynamical decoupling sequences

E Takou, E Barnes, SE Economou

Phys. Rev. X 13, 011004 (2023)

Leakage Reduces Device Coherence Demands for Pulse-Level Molecular Simulations

A Asthana, C Liu, OR Meitei, SE Economou, E Barnes, NJ Mayhall

Phys. Rev. Applied 19, 064071 (2023)

Extracting perfect GHZ states from imperfect weighted graph states via entanglement concentration

R Frantzeskakis, C Liu, Z Raissi, E Barnes, Sophia E Economou

Phys. Rev. Research 5, 023124 (2023)

Solving Nuclear Structure Problems with the Adaptive Variational Quantum Algorithm

AM Romero, J Engel, HL Tang, Sophia E Economou

Phys. Rev. C 105, 064317 (2022)

Preparing exact eigenstates of the open XXZ chain on a quantum computer

John S Van Dyke, Edwin Barnes, Sophia E Economou, Rafael I Nepomechie

Journal of Physics A: Mathematical and Theoretical 55, 055301 (2022)

Avoiding symmetry roadblocks and minimizing the measurement overhead of adaptive variational quantum eigensolvers

VO Shkolnikov, Nicholas J Mayhall, Sophia E Economou, Edwin Barnes

Quantum 7, 1040 (2023)

Entangled photon factory: How to generate quantum resource states from a minimal number of quantum emitters

Bikun Li, Sophia E Economou, Edwin Barnes

npj Quantum Information 8, 1 (2022)

Robust photon-mediated entangling gates between quantum dot spin qubits

Ada Warren, Utkan Güngördü, JP Kestner, Edwin Barnes, Sophia E Economou

Phys. Rev. B 104, 115308 (2021) 

Preserving symmetries for variational quantum eigensolvers in the presence of noise

George S. Barron, Bryan T. Gard, Orien J. Altman, Nicholas J. Mayhall, Edwin Barnes, Sophia E. Economou

Phys. Rev. Applied 16, 034003 (2021)

Building a Quantum Engineering Undergraduate Program

Abraham Asfaw, Alexandre Blais, Kenneth R Brown, Jonathan Candelaria, Christopher Cantwell, Lincoln D Carr, Joshua Combes, Dripto M Debroy, John M Donohue, Sophia E Economou, et al.

IEEE Transactions on Education, doi: 10.1109/TE.2022.3144943

Protecting quantum information in quantum dot spin chains by driving exchange interactions periodically

John S Van Dyke, Yadav P Kandel, Haifeng Qiao, John M Nichol, Sophia E Economou, Edwin Barnes

Phys. Rev. B 103, 245303 (2021)

Driven dynamics of a quantum dot electron spin coupled to a bath of higher-spin nuclei

Arian Vezvaee, Girish Sharma, Sophia E Economou, Edwin Barnes

Phys. Rev. B 103, 235301 (2021)

Optical control protocols for high-fidelity spin rotations of single SiV and SnV centers in diamond

(Editor's suggestion)

Evangelia Takou and Sophia E. Economou

Phys. Rev. B 104, 115302 (2021)

Sensitive spin seeks single magnon

Paul Hilaire and Sophia E. Economou

Nature Physics 17, 551 (2021)

qubit-ADAPT-VQE: An adaptive algorithm for constructing hardware-efficient ansätze on a quantum processor

Ho Lun Tang, V. O. Shkolnikov, George S. Barron, Harper R. Grimsley, Nicholas J. Mayhall, Edwin Barnes, Sophia E. Economou

PRX Quantum 2, 020310 (2021)

Preparing Bethe Ansatz Eigenstates on a Quantum Computer

John S Van Dyke, George S Barron, Nicholas J Mayhall, Edwin Barnes, Sophia E. Economou

PRX Quantum 2, 040329 (2021)

A universal quantum gate set for transmon qubits with strong ZZ interactions

Junling Long, Tongyu Zhao, Mustafa Bal, Ruichen Zhao, George S Barron, Hsiang-sheng Ku, Joel A Howard, Xian Wu, Corey Rae H McRae, Xiu-Hao Deng, Guilhem J Ribeill, Meenakshi Singh, Thomas A Ohki, Edwin Barnes, Sophia E Economou, David P Pappas

arXiv:2103.12305

Doubly geometric quantum control

Wenzheng Dong, Fei Zhuang, Sophia E Economou, Edwin Barnes

PRX Quantum 2, 030333 (2021)

Noise-resistant Landau-Zener sweeps from geometrical curves

Fei Zhuang, Junkai Zeng, Sophia E Economou, Edwin Barnes

Quantum 6, 639 (2022)

Development of quantum interconnects (quics) for next-generation information technologies

David Awschalom, Karl K Berggren, Hannes Bernien, Sunil Bhave, Lincoln D Carr, Paul Davids, Sophia E Economou, Dirk Englund, Andrei Faraon, et al.

PRX Quantum 2, 017002 (2021)

Quantum simulators: Architectures and opportunities

Ehud Altman, Kenneth R Brown, Giuseppe Carleo, Lincoln D Carr, Eugene Demler, Cheng Chin, Brian DeMarco, Sophia E Economou, Mark A Eriksson, Kai-Mei C Fu, et al.

PRX Quantum 2, 017003 (2021)

Resource requirements for efficient quantum communication using all-photonic graph states generated from a few matter qubits

Paul Hilaire, Edwin Barnes, Sophia E Economou

Quantum 5, 397 (2021)

Fast high-fidelity single-qubit gates for flip-flop qubits in silicon

Fernando A Calderon-Vargas, Edwin Barnes, Sophia E Economou

arXiv:2101.11592

Error-correcting entanglement swapping using a practical logical photon encoding

Paul Hilaire, Edwin Barnes, Sophia E Economou, Frédéric Grosshans

Phys. Rev. A 104, 052623 (2021)

Multiconfigurational study of the negatively charged nitrogen-vacancy center in diamond

Churna Bhandari, Aleksander L Wysocki, Sophia E Economou, Pratibha Dev, Kyungwha Park

Phys. Rev. B 103, 014115 (2021)

Gate-free state preparation for fast variational quantum eigensolver simulations: ctrl-VQE

Oinam Romesh Meitei, Bryan T Gard, George S Barron, David P Pappas, Sophia E Economou, Edwin Barnes, Nicholas J Mayhall

npj Quantum Information 7, 155 (2021)

Precise high-fidelity electron–nuclear spin entangling gates in NV centers via hybrid dynamical decoupling sequences

Wenzheng Dong, FA Calderon-Vargas, Sophia E Economou

New Journal of Physics 22, 073059 (2020)

Adaptive quantum approximate optimization algorithm for solving combinatorial problems on a quantum computer

Linghua Zhu, Ho Lun Tang, George S Barron, FA Calderon-Vargas, Nicholas J Mayhall, Edwin Barnes, Sophia E Economou

Phys. Rev. Research 4, 033029 (2022)

Fast noise-resistant control of donor nuclear spin qubits in silicon

James Simon, FA Calderon-Vargas, Edwin Barnes, Sophia E Economou

Phys. Rev. B 101, 205307 (2020)

Teaching quantum information science to high-school and early undergraduate students

Sophia E Economou, Terry Rudolph, Edwin Barnes

arXiv:2005.07874

Discrete time crystal in the gradient-field Heisenberg model

Bikun Li, John S Van Dyke, Ada Warren, Sophia E Economou, Edwin Barnes

Phys. Rev. B 101, 115303 (2020)

Microwave-based arbitrary CPHASE gates for transmon qubits

George S Barron, Fernando A Calderon-Vargas, Junling Long, David P Pappas, Sophia E Economou

Phys. Rev. B 101, 054508 (2020)

Efficient symmetry-preserving state preparation circuits for the variational quantum eigensolver algorithm

Bryan T Gard, Linghua Zhu, George S Barron, Nicholas J Mayhall, Sophia E Economou, Edwin Barnes

npj Quantum Information 6, 1 (2020)

Is the trotterized uccsd ansatz chemically well-defined?

Harper R Grimsley, Daniel Claudino, Sophia E Economou, Edwin Barnes, Nicholas J Mayhall

J. Chem. Theory Comput. 16, 1 (2020)

Toward long-range entanglement between electrically driven single-molecule magnets

Khadijeh Najafi, Aleksander L Wysocki, Kyungwha Park, Sophia E Economou, Edwin Barnes

J. Phys. Chem. Lett. 10, 7347 (2019)

Long-distance entangling gates between quantum dot spins mediated by a superconducting resonator

Ada Warren, Edwin Barnes, Sophia E Economou

Phys. Rev. B 100, 161303(R) (2019)

Spin-dependent quantum optics in a quantum dot molecule

Bumsu Lee, Brennan C Pursley, Samuel G Carter, Sophia E Economou, Michael K Yakes, Joel Q Grim, Allan S Bracker, Daniel Gammon

Phys. Rev. B 100, 125438 (2019)

Deterministic generation of large-scale entangled photonic cluster state from interacting solid state emitters

Mercedes Gimeno-Segovia, Terry Rudolph, Sophia E Economou

Phys. Rev. Lett. 123, 070501 (2019)

Fast high-fidelity entangling gates for spin qubits in Si double quantum dots

FA Calderon-Vargas, George S Barron, Xiu-Hao Deng, AJ Sigillito, Edwin Barnes, Sophia E Economou

Phys. Rev. B 100, 035304 (2019)

An adaptive variational algorithm for exact molecular simulations on a quantum computer

Harper R Grimsley, Sophia E Economou, Edwin Barnes, Nicholas J Mayhall

Nature communications 10, 1 (2019)

Enhancement of nuclear spin coherence times by driving dynamic nuclear polarization at defect centers in solids

Girish Sharma, Torsten Gaebel, Ewa Rej, David J Reilly, Sophia E Economou, Edwin Barnes

Phys. Rev. B 99, 205423 (2019)

Generation of arbitrary all-photonic graph states from quantum emitters

Antonio Russo, Edwin Barnes, Sophia E Economou

New Journal of Physics 21, 055002 (2019)

Spin polarization through intersystem crossing in the silicon vacancy of silicon carbide

Wenzheng Dong, MW Doherty, Sophia E Economou

Phys. Rev. B 99, 184102 (2019)

Solvable quantum model of dynamic nuclear polarization in optically driven quantum dots

Thomas Nutz, Edwin Barnes, Sophia E Economou

Phys. Rev. B 99, 035439 (2019)

Stabilization and manipulation of multispin states in quantum-dot time crystals with Heisenberg interactions

Edwin Barnes, John M Nichol, Sophia E Economou

Phys. Rev. B 99, 035311 (2019)

Adiabatically preparing quantum dot spin states in the Voigt geometry

Emmanuel Paspalakis, Sophia E Economou, Fernando Carreño

Journal of Applied Physics 125, 024305 (2019)

Dynamic nuclear polarization from topological insulator helical edge states

Antonio Russo, Edwin Barnes, Sophia E Economou

Phys. Rev. B 98, 235412 (2018)

Photonic graph state generation from quantum dots and color centers for quantum communications

Antonio Russo, Edwin Barnes, Sophia E Economou

Phys. Rev. B 98, 085303 (2018)

Topological insulator ring with magnetic impurities

Arian Vezvaee, Antonio Russo, Sophia E Economou, Edwin Barnes

Phys. Rev. B 98, 035301 (2018)

Quantum properties of dichroic silicon vacancies in silicon carbide

Roland Nagy, Matthias Widmann, Matthias Niethammer, Durga BR Dasari, Ilja Gerhardt, Öney O Soykal, Marina Radulaski, Takeshi Ohshima, Jelena Vučković, Nguyen Tien Son, Ivan G Ivanov, Sophia E Economou, Cristian Bonato, Sang-Yun Lee, Jörg Wrachtrup

Phys. Rev. Applied 9, 034022 (2018)

Single qubit operations using microwave hyperbolic secant pulses

Hsiang S Ku, JL Long, Xian Wu, Mustafa Bal, RE Lake, Edwin Barnes, Sophia E Economou, David P Pappas

Phys. Rev. A 96, 042339 (2017)

Deterministic generation of all-photonic quantum repeaters from solid-state emitters

Donovan Buterakos, Edwin Barnes, Sophia E Economou

Phys. Rev. X 7, 041023 (2017)

Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides

Girish Sharma, Sophia E Economou, Edwin Barnes

Phys. Rev. B 96, 125201 (2017)

Robustness of error-suppressing entangling gates in cavity-coupled transmon qubits

Xiu-Hao Deng, Edwin Barnes, Sophia E Economou

Phys. Rev. B 96, 035441 (2017)

Fast microwave-driven three-qubit gates for cavity-coupled superconducting qubits

Edwin Barnes, Christian Arenz, Alexander Pitchford, Sophia E Economou

Phys. Rev. B 96, 024504 (2017)

Spin-photon entanglement interfaces in silicon carbide defect centers

Sophia E Economou and Pratibha Dev

Nanotechnology 27, 504001 (2016)

Silicon vacancy center in 4 H-SiC: Electronic structure and spin-photon interfaces

ÖO Soykal, Pratibha Dev, Sophia E Economou

Phys. Rev. B 93, 081207(R) (2016)

Spin coherence and echo modulation of the silicon vacancy in 4 H− SiC at room temperature

SG Carter, ÖO Soykal, Pratibha Dev, Sophia E Economou, ER Glaser

Phys. Rev. B 92, 161202(R) (2015)

Two-photon absorption by a quantum dot pair

Michael Scheibner, Sophia E Economou, Ilya V Ponomarev, Cameron Jennings, Allan S Bracker, Daniel Gammon

Phys. Rev. B 92, 081411(R) (2015)

Spin–cavity interactions between a quantum dot molecule and a photonic crystal cavity

Patrick M Vora, Allan S Bracker, Samuel G Carter, Timothy M Sweeney, Mijin Kim, Chul Soo Kim, Lily Yang, Peter G Brereton, Sophia E Economou, Daniel Gammon

Nature Communications 6, 1 (2015)

Analytical approach to swift nonleaky entangling gates in superconducting qubits

Sophia E. Economou and Edwin Barnes

Phys. Rev. B 91, 161405(R) (2015)

Excitation spectrum as a resource for efficient two-qubit entangling gates

Dmitry Solenov, Sophia E Economou, Thomas L Reinecke

Phys. Rev. B 89, 155404 (2014)

Theory of dynamic nuclear polarization and feedback in quantum dots

Sophia E Economou and Edwin Barnes

Phys. Rev. B 89, 165301 (2014)

All-optical tomography of electron spins in (In, Ga) As quantum dots

S Varwig, A René, Sophia E Economou, A Greilich, DR Yakovlev, D Reuter, AD Wieck, TL Reinecke, M Bayer

Phys. Rev. B 89, 081310(R) (2014)

Strong hyperfine-induced modulation of an optically driven hole spin in an InAs quantum dot

Samuel G Carter, Sophia E Economou, Alex Greilich, Edwin Barnes, T Sweeney, Allan S Bracker, Daniel Gammon

Phys. Rev. B 89, 075316 (2014)

Two-qubit quantum gates for defect qubits in diamond and similar systems

Dmitry Solenov, Sophia E Economou, Thomas L Reinecke

Phys. Rev. B 88, 161403(R) (2013)

Quantum control of a spin qubit coupled to a photonic crystal cavity

Samuel G Carter, Timothy M Sweeney, Mijin Kim, Chul Soo Kim, Dmitry Solenov, Sophia E Economou, Thomas L Reinecke, Lily Yang, Allan S Bracker, Daniel Gammon

Nature Photonics 7, 329 (2013)

Fast two-qubit gates for quantum computing in semiconductor quantum dots using a photonic microcavity

Dmitry Solenov, Sophia E Economou, TL Reinecke

Phys. Rev. B 87, 035308 (2013)

Putting a spin on photon entanglement

Sophia E. Economou

Nature 491, 343 (2012)

Scalable qubit architecture based on holes in quantum dot molecules

Sophia E Economou, Juan I Climente, Antonio Badolato, Allan S Bracker, Daniel Gammon, Matthew F Doty

Phys. Rev. B 86, 085319 (2012)

High-fidelity quantum gates via analytically solvable pulses

Sophia E Economou

Phys. Rev. B 85, 241401(R) (2012)

Entangled photon pair generation with quantum dot molecules

Michael Scheibner, Sophia E Economou, Allan S Bracker, Daniel Gammon, Ilya V Ponomarev

J. Opt. Soc. Am. B 29, A82 (2012)

Optical control of coherent interactions between electron spins in InGaAs quantum dots

S Spatzek, A Greilich, Sophia E Economou, S Varwig, A Schwan, DR Yakovlev, D Reuter, AD Wieck, TL Reinecke, M Bayer

Phys. Rev. Lett. 107, 137402 (2011)

Electron-nuclear dynamics in a quantum dot under nonunitary electron control

Edwin Barnes and Sophia E Economou

Phys. Rev. Lett. 107, 047601 (2011)

Controlling the nuclear polarization in quantum dots using optical pulse shape with a modest bandwidth

SG Carter, Sophia E Economou, A Shabaev, AS Bracker

Phys. Rev. B 83, 115325 (2011)

Optically generated 2-dimensional photonic cluster state from coupled quantum dots

Sophia E Economou, Netanel Lindner, Terry Rudolph

Phys. Rev. Lett. 105, 093601 (2010)

Directing nuclear spin flips in InAs quantum dots using detuned optical pulse trains

SG Carter, A Shabaev, Sophia E Economou, TA Kennedy, AS Bracker, TL Reinecke

Phys. Rev. Lett. 102, 167403 (2009)

Ultrafast optical rotations of electron spins in quantum dots

A Greilich, Sophia E Economou, S Spatzek, DR Yakovlev, D Reuter, AD Wieck, TL Reinecke, M Bayer

Nature Physics 5, 262 (2009)

Optical spin initialization and nondestructive measurement in a quantum dot molecule

Danny Kim, Sophia E Economou, Ştefan C Bădescu, Michael Scheibner, Allan S Bracker, Mark Bashkansky, Thomas L Reinecke, Daniel Gammon

Phys. Rev. Lett. 101, 236804 (2008)

Optically induced spin gates in coupled quantum dots using the electron-hole exchange interaction

Sophia E Economou and TL Reinecke

Phys. Rev. B 78, 115306 (2008)

Theory of fast optical spin rotation in a quantum dot based on geometric phases and trapped states

Sophia E Economou and TL Reinecke

Phys. Rev. Lett. 99, 217401 (2007)

Selective Optical Control of Electron Spin Coherence in Singly Charged GaAs− Al 0.3 Ga 0.7 As Quantum Dots

Yanwen Wu, Erik D Kim, Xiaodong Xu, Jun Cheng, DG Steel, AS Bracker, D Gammon, Sophia E Economou, LJ Sham

Phys. Rev. Lett. 99, 097402 (2007)

Theory of nonlinear optical spectroscopy of electron spin coherence in quantum dots

Ren-Bao Liu, SE Economou, LJ Sham, DG Steel

Phys. Rev. B 75, 085322 (2007)

Proposal for optical U (1) rotations of electron spin trapped in a quantum dot

Sophia E Economou, LJ Sham, Yanwen Wu, DG Steel

Phys. Rev. B 74, 205415 (2006)

Ultrafast optical control of electron spin coherence in charged GaAs quantum dots

MV Gurudev Dutt, Jun Cheng, Yanwen Wu, Xiaodong Xu, DG Steel, AS Bracker, D Gammon, Sophia E Economou, Ren-Bao Liu, LJ Sham

Phys. Rev. B 74, 125306 (2006)

Stimulated and spontaneous optical generation of electron spin coherence in charged GaAs quantum dots

MV Gurudev Dutt, Jun Cheng, Bo Li, Xiaodong Xu, Xiaoqin Li, PR Berman, DG Steel, AS Bracker, D Gammon, Sophia E Economou, Ren-Bao Liu, LJ Sham

Phys. Rev. Lett. 94, 227403 (2005)

Unified theory of consequences of spontaneous emission in a Λ system

Sophia E Economou, Ren-Bao Liu, LJ Sham, DG Steel

Phys. Rev. B 71, 195327 (2005)