
extra space space space 
Our work is in quantum information, specifically `Models of quantum computation' and quantum faulttolerance. For more information click here.
Featured publication: Wigner Function Negativity and Contextuality in Quantum Computation on Rebits. [Posted May 4, 2015] We describe a universal scheme of quantum computation by state injection on rebits (states with real density matrices). For this scheme, we establish contextuality and Wigner function negativity as computational resources, extending results of M. Howard et al. [Nature (London) 510, 351 (2014)] to twolevel systems. For this purpose, we define a Wigner function suited to systems of multiple rebits and prove a corresponding discrete Hudson's theorem. We introduce contextuality witnesses for rebit states and discuss the compatibility of our result with stateindependent contextuality.
sp 
Negativity and contextuality for rebits. Left: Rebit Wigner function of a threequbit graph state. This state is local unitary equivalent to a GreenbergerHorneZeilinger (GHZ) state. Negativity of the Wigner function for the threequbit graph state indicates nonclassicality. Contrary to qudits in odd prime dimension, for rebits negativity is not synonymous wit contextuality. Nevertheless, the negativity in the Wigner function for the threequbit graph state is strong enough to witness contextuality. Right: From the perspective of contextuality in quantum computation with magic states, Mermin's square and star, and all their cousins, are ``little monsters''. For explanation, see below. 
Stateindependent contextuality, as exhibited by Mermin's square and star, provides beautifully simple proofs for the KochenSpecker theorem in dimension 4 and higher. However, for establishing contextuality as a resource only posessed by magic states, stateindependent contextuality poses a problem: If ``cheap'' Pauli measurements already have contextuality, then how can one say that contextuality is a key resource provided by the magic states? For qudits, the problem doesn't exist because there is no stateindependent contextuality w.r.t. Pauli measurements. For rebits, the problem is overcome by the operational restriction to CSSness preserving gates and measurements.
Click here for previous posts.
extra space  
extra space  
extra space 
Robert Raussendorf 

extra space  
extra space 
Andrew Elias 

extra space  
extra space 
Poya Haghnegahdar 

extra space  
extra space 
Oleg Kabernik 

extra space  
extra space 
David Stephen 

extra space  
extra space 
Emily Tyhurst 

extra space  
extra space 
Dong Sheng Wang 

extra space  
extra space 
Arman Zaribafiyan 
TzuChieh Wei, faculty at Stony Brook, NY, USA
Pradeep Sarvepalli, faculty at IIT Madras, Chennai, India
Leon Loveridge, University of Oxford, UK
Raouf Dridi, 1Qbit, Vancouver
Vijay Singh, Indian Institute of Technology, Bombay
Angela Ruthven (UBC Enginerring Physics)
Len Goff (UBC Economics)
Matthew Scholte
Cedric Lin (MIT),
Matthew Low (University of Chicago),
Philip Ketterer (Ludwig Maximilians University Munich, Germany),
Philip Allen Mar (University of Toronto),
Cihan Okay (University of Western Ontario),
Philippe Alard Guerin (University of Vienna, PhD)
Navid Siami
David T. Stephen, DongSheng Wang, Abhishodh Prakash, TzuChieh Wei, Robert Raussendorf, Determining the computational power of symmetry protected topological phases, arXiv:1611.08053v1
Juan BermejoVega, Nicolas Delfosse, Dan E. Browne, Cihan Okay, Robert Raussendorf, Contextuality as a resource for qubit quantum computation, arXiv:1610.08529v2
Nicolas Delfosse, Cihan Okay, Juan BermejoVega, Dan E. Browne, Robert Raussendorf , Equivalence between contextuality and negativity of the Wigner function for qudits, arXiv:1610.07093v1
Robert Raussendorf, Dongsheng Wang, Abhishodh Prakash, TzuChieh Wei, David Stephen, Symmetryprotected topological phases with uniform computational power in one dimension , arXiv:1609.07549v1
DongSheng Wang, David T. Stephen, Robert Raussendorf, Qudit quantum computation on matrix product states with global symmetry, arXiv:1609.07174v1
Robert Raussendorf, Cohomological framework for contextual quantum computations, arXiv:1602.04155v2
Raussendorf, R.; Sarvepalli, P.; Wei, T. C., Haghnegahdar, P., Symmetry constraints on temporal order in measurementbased quantum computation , Information and Computation 250, 115138 (2016).
TzuChieh Wei and Robert Raussendorf, Universal measurementbased quantum com putation with spin2 AffleckKennedyLiebTasaki states, Phys. Rev. A 92, 012310 (2015).
Nicolas Delfosse, J. Bian, P. Allard Guerin, R. Raussendorf, Contextuality and Wigner negativity in quantum computation on rebits, Phys Rev X 5, 021003 (2015).
Loveridge L, Dridi R, Raussendorf R., Topos logic in measurementbased quantum computation, Proc. R. Soc. A 471: 20140716 (2015).
T.C. Wei, P. Haghnegahdar and R. Raussendorf, Hybrid valencebond states for universal quantum computation, Phys. Rev. A 90, 042333 (2014).
M.J. Hoban, J.J. Wallman, H. Anwar, N. Usher, R. Raussendorf, D.E. Browne, Measurementbased classical computation, Phys. Rev. Lett 112, 140505 (2014). [Editors pick].
C. Monroe, R. Raussendorf, A. Ruthven, K. Brown, P. Maunz, L.M. Duan and J. Kim, Large Scale Modular Quantum Computer Architecture with Atomic Memory and Photonic Interconnects, Phys Rev A 89, 22317 (2014) [selected for Physics spotlight].
R. Raussendorf, Contextuality in measurementbased quantum computation, Phys. Rev. A 88, 022322 (2013).
Leonard Goff and Robert Raussendorf, Classical simulation of measurementbased quantum computation with highergenus surface code states, Phys. Rev. A 86, 042301 (2012).
R. Raussendorf, P. Sarvepalli, T.C. Wei, P. Haghnegahdar, Symmetry constraints on tem poral order in measurementbased quantum computation, Electronic Proceedings in Theoretical Computer Science (EPTCS) 95, pp. 219250 (2012).
TzuChieh Wei, Ian Affleck, Robert Raussendorf, The 2D AKLT state on the honeycomb lattice is a universal resource for quantum computation, Phys. Rev. A 86, 032328 (2012).
R. Raussendorf, Key concepts in faulttolerant quantum computation, Philosophical transactions. Series A, Mathematical, physical, and engineering sciences 370, 454 (2012).
Robert Raussendorf and TzuChieh Wei, Quantum Computation by Local Measurement, Annu. Rev. Condens. Matter Phys 3, 239 (2012).
XingCan Yao, TianXiong Wang, HaoZe Chen, WeiBo Gao, Austin G. Fowler, Robert Raussendorf, ZengBing Chen, NaiLe Liu, ChaoYang Lu, YouJin Deng, YuAo Chen, and JianWei Pan, Experimental demonstration of topological error correction, Nature 482, 489 (2012).
P. Sarvepalli and R. Raussendorf, Efficient decoding of topological color codes, Phys. Rev. A 85, 022317 (2012).
Roman Orus and TzuChieh Wei, Geometric entanglement of onedimensional systems: bounds and scalings in the thermodynamic limit, Quantum Information and Computation Vol. 11, No. 7, 563 (2011).
Jingfu Zhang, TzuChieh Wei, and Raymond Laflamme, Experimental Quantum Simulation of Entanglement in Manybody Systems, Phys. Rev. Lett. 107, 010501 (2011).
Ying Li, Daniel E. Browne, Leong Chuan Kwek, Robert Raussendorf, and TzuChieh Wei, Thermal States as Universal Resources for Quantum Computation with Alwayson Interactions, Phys. Rev. Lett. 107, 060501 (2011).
P. Sarvepalli, Topological Color Codes over Higher Alphabet. In Proc. of IEEE Information Theory Workshop, Dublin, Ireland Aug 30Sep 3, 2010.
P. Sarvepalli, R. Raussendorf. Local equivalence of surface code states. TQC'10 Proceedings of the 5th conference on Theory of quantum computation, communication, and cryptography. Lecture Notes in Computer Science, 2011, Volume 6519/2011, 4762.
Pradeep Sarvepalli, Entropic Inequalities for a Class of Quantum Secret Sharing States, Phys. Rev. A 83, 042303 (2011).
Pradeep Sarvepalli, Bounds on the Information Rate of Quantum Secret Sharing Schemes, Phys. Rev. A 83, 042324 (2011).
TzuChieh Wei, Johnathan Lavoie, and Rainer Kaltenbaek, Creating multiphoton polarization boundentangled states, Phys. Rev. A 83, 033839 (2011).
Lin Chen, Huangjun Zhu, and TzuChieh Wei, Connections of geometric measure of entanglement of pure symmetric states to quantum state estimation Phys. Rev. A 83, 012305 (2011).
TzuChieh Wei, Smitha Vishveshwara and Paul M. Goldbart, Global geometric entanglement in transversefield XY spin chains: finite and infinite systems, Quantum Inf. Comput. 11, 03260354 (2011)
TzuChieh Wei, Ian Affleck, Robert Raussendorf, The 2D AKLT state is a universal quantum computational resource, Physical Review Letters 106, 070501 (2011).
P. Sarvepalli, Topological Color Codes over Higher Alphabet. In Proc. of IEEE Information Theory Workshop, Dublin, Ireland Aug 30Sep 3, 2010.
R. Raussendorf, Shaking up ground states Nature Physics 6, 840 (2010); News and Views on J. Lavoie et al., Optical oneway quantum computing with a simulated valencebond solid , Nature Physics 6, 850 (2010).
Roman Orus and TzuChieh Wei, Visualizing elusive phase transitions with geometric entanglement, Phys. Rev. B 82, 155120 (2010).
Wade DeGottardi, TzuChieh Wei, Victoria Fernandez, and Smitha Vishveshwara, Accessing nanotube bands via crossed electric and magnetic fields, Phys. Rev. B 82, 155411 (2010).
Pradeep Sarvepalli and Robert Raussendorf, On Local Equivalence, Surface Code States and Matroids, Phys. Rev. A 82, 022304 (2010).
Matthew Killi, TzuChieh Wei, Ian Affleck, Arun Paramekanti, TomonagaLuttinger liquid physics in gated bilayer graphene , Phys. Rev. Lett. 104, 216406 (2010).
TzuChieh Wei, Entanglement under the renormalizationgroup transformations on quantum states and in quantum phase transitions , Phys. Rev. A 81, 062313 (2010).
TzuChieh Wei, Exchange symmetry and global entanglement and full separability , Phys. Rev. A 81, 054102 (2010).
Pradeep Sarvepalli and Robert Raussendorf, Matroids and Quantum Secret Sharing Schemes, Phys. Rev. A 81, 052333 (2010).
Pradeep Sarvepalli and Andreas Klappenecker, Degenerate quantum codes and the quantum Hamming bound, Phys. Rev. A 81, 032318 (2010).
TzuChieh Wei, Michele Mosca, and Ashwin Nayak, Interacting boson problems can be QMAhard, Phys. Rev. Lett. 104, 040501 (2010).
M. Van den Nest, W. Duer, R. Raussendorf, H. J. Briegel, Quantum algorithms for spin models and simulable gate sets for quantum computation, Phys. Rev. A 80, 052334 (2009).
Robert Raussendorf, Measurementbased quantum computation with cluster states ( PhD thesis, LudwigMaximiliansUniversitaet Munich, 2003), Int. J. of Quantum Information 7, 1053  1203 (2009).
Sayatnova Tamaryan, TzuChieh Wei, and DaeKil Park, Maximally entangled threequbit states via geometric measure of entanglement, Phys. Rev. A 80, 052315 (2009).
Pradeep Kiran Sarvepalli and Andreas Klappenecker, Sharing classical secrets with CalderbankShorSteane codes, Phys. Rev. A 80, 022321 (2009).
H. J. Briegel, D. E. Browne, W. Duer, R. Raussendorf and M. Van den Nest, Measurementbased quantum computation, Nature Physics 5, 19 (2009).