M. Steffen, M. Ansmann, R. C. Bialczak, N. Katz, E. Lucero, R. McDermott, M. Neeley, E. M. Weig, A. N. Cleland, and J. M. Martinis, "Measurement of the entanglement of two superconducting qubits via state tomography," Science 313, 1423-1425 (2006).

[Crossref]
[PubMed]

A. Gilchrist, N. K. Langford, and M. A. Nielsen, "Distance measures to compare real and ideal quantum processes," Phys. Rev. A 71, 062310 (2005).

[Crossref]

N. K. Langford, T. J. Weinhold, R. Prevedel, A. Gilchrist, J. L. O'Brien, G. J. Pryde, and A. G. White, "Demonstration of a simple entangling optical gate and its use in Bell-state analysis," Phys. Rev. Lett. 95, 210504 (2005).

[Crossref]
[PubMed]

H. F. Hofmann, "Complementary classical fidelities as an efficient criterion for the evaluation of experimentally realized quantum operations," Phys. Rev. Lett. 94, 160504 (2005).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

G. M. D'Ariano and P. L. Presti, "Imprinting a complete information about a quantum channel on its output state," Phys. Rev. Lett. 91, 047902 (2003).

[Crossref]
[PubMed]

F. De Martini, A. Mazzei, M. Ricci, and G. M. D'Ariano, "Exploiting quantum parallelism of entanglement for a complete experimental quantum characterization of a single qubit device," Phys. Rev. A 67, 062307 (2003).

[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
[PubMed]

M. Barbieri, F. De Martini, G. Di Nepi, P. Mataloni, G. M. D'Ariano, and C. Macchiavello, "Detection of entanglement with polarized photons: experimental realization of an entanglement witness," Phys. Rev. Lett. 91, 227901 (2003).

[Crossref]
[PubMed]

O. Gühne, P. Hyllus, D. Bruß, A. Ekert, M. Lewenstein, C. Macchiavello, and A. Sanpera, "Detection of entanglement with few local measurements," Phys. Rev. A 66, 062305 (2002).

[Crossref]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

J. L. Dodd and M. A. Nielsen, "A simple operational interpretation of the fidelity," Phys. Rev. A 66, 044301 (2002).

[Crossref]

M. A. Nielsen, "A simple formula for the average gate fidelity of a quantum dynamical operation," Phys. Lett. A 303, 249-252 (2002).

[Crossref]

J. I. Cirac, W. Dür, B. Kraus, and M. Lewenstein, "Entangling operations and their implementation using a small amount of entanglement," Phys. Rev. Lett. 86, 544-547 (2001).

[Crossref]
[PubMed]

A. M. Childs, I. L. Chuang, and D. W. Leung, "Realization of quantum process tomography in NMR," Phys. Rev. A 64, 012314 (2001).

[Crossref]

W. J. Munro, K. Nemoto, and A. G. White, "The Bell inequality: a measure of entanglement?" J. Mod. Opt. 48, 1239-1246 (2001).

[Crossref]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

D. F. V. James, P. G. Kwiat, W. J. Munro, and A. G. White, "Measurement of qubits," Phys. Rev. A 64, 052312 (2001).

[Crossref]

A. G. White, D. F. V. James, W. J. Munro, and P. G. Kwiat, "Exploring Hilbert space: accurate characterization of quantum information," Phys. Rev. A 65, 012301 (2001).

[Crossref]

B. M. Terhal, "Bell inequalities and the separability criterion," Phys. Lett. A 271, 319-326 (2000).

[Crossref]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
[PubMed]

B. M. Terhal and P. Horodecki, "Schmidt number for density matrices," Phys. Rev. A 61, 040301(R) (2000).

[Crossref]

V. Coffman, J. Kundu, and W. K. Wootters, "Distributed entanglement," Phys. Rev. A 61, 052306 (2000).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "General teleportation channel, singlet fraction, and quasidistillation," Phys. Rev. A 60, 1888-1898 (1999).

[Crossref]

A. G. White, D. F. V. James, P. H. Eberhard, and P. G. Kwiat, "Nonmaximally entangled states: production, characterization, and utilization," Phys. Rev. Lett. 83, 3103-3107 (1999).

[Crossref]

W. K. Wootters, "Entanglement of formation of an arbitrary state of two qubits," Phys. Rev. Lett. 80, 2245-2248 (1998).

[Crossref]

M. A. Nielsen, E. Knill, and R. Laflamme, "Complete quantum teleportation using nuclear magnetic resonance," Nature 396, 52-55 (1998).

[Crossref]

I. L. Chuang and M. A. Nielsen, "Prescription for experimental determination of the dynamics of a quantum black box," J. Mod. Opt. 44, 732-744 (1997).

J. F. Poyatos, J. I. Cirac, and P. Zoller, "Complete characterization of a quantum process: the two-bit quantum gate," Phys. Rev. Lett. 78, 390-393 (1997).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "Separability of mixed states: necessary and sufficient conditions," Phys. Lett. A 223, 1-8 (1996).

[Crossref]

A. Jamiolkowski, "Linear transformations which preserve trace and positive semidefiniteness of operators," Rep. Math. Phys. 3, 275-278 (1972).

[Crossref]

J. F. Clauser, M. A. Horne, A. Shimony, and R. A. Holt, "Proposed experiment to test local hidden-variable theories," Phys. Rev. Lett. 23, 880-884 (1969).

[Crossref]

J. S. Bell, "On the Einstein-Podolsky-Rosen paradox," Physics (Long Island City, N.Y.) 1, 195-200 (1964).

[Crossref]

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N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

M. Steffen, M. Ansmann, R. C. Bialczak, N. Katz, E. Lucero, R. McDermott, M. Neeley, E. M. Weig, A. N. Cleland, and J. M. Martinis, "Measurement of the entanglement of two superconducting qubits via state tomography," Science 313, 1423-1425 (2006).

[Crossref]
[PubMed]

M. Barbieri, F. De Martini, G. Di Nepi, P. Mataloni, G. M. D'Ariano, and C. Macchiavello, "Detection of entanglement with polarized photons: experimental realization of an entanglement witness," Phys. Rev. Lett. 91, 227901 (2003).

[Crossref]
[PubMed]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

J. S. Bell, "On the Einstein-Podolsky-Rosen paradox," Physics (Long Island City, N.Y.) 1, 195-200 (1964).

[Crossref]

M. Steffen, M. Ansmann, R. C. Bialczak, N. Katz, E. Lucero, R. McDermott, M. Neeley, E. M. Weig, A. N. Cleland, and J. M. Martinis, "Measurement of the entanglement of two superconducting qubits via state tomography," Science 313, 1423-1425 (2006).

[Crossref]
[PubMed]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

R. Blume-Kohout and P. Hayden, "Accurate quantum state estimation via 'Keeping the experimentalist honest'," arXiv.org e-Print archive, quantum physics/0603116, 14 March 2006, http://www.arxiv.org/abs/quant-ph/0603116.

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
[PubMed]

N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

O. Gühne, P. Hyllus, D. Bruß, A. Ekert, M. Lewenstein, C. Macchiavello, and A. Sanpera, "Detection of entanglement with few local measurements," Phys. Rev. A 66, 062305 (2002).

[Crossref]

J. L. Brylinski and R. K. Brylinski, "Computational mathematics," in Mathematics of Quantum Computation, R.K.Brylinski and G.Chen, eds. (Chapman & Hall/CRC Press, 2002), Chap. 2.

J. L. Brylinski and R. K. Brylinski, "Computational mathematics," in Mathematics of Quantum Computation, R.K.Brylinski and G.Chen, eds. (Chapman & Hall/CRC Press, 2002), Chap. 2.

A. M. Childs, I. L. Chuang, and D. W. Leung, "Realization of quantum process tomography in NMR," Phys. Rev. A 64, 012314 (2001).

[Crossref]

A. M. Childs, I. L. Chuang, and D. W. Leung, "Realization of quantum process tomography in NMR," Phys. Rev. A 64, 012314 (2001).

[Crossref]

I. L. Chuang and M. A. Nielsen, "Prescription for experimental determination of the dynamics of a quantum black box," J. Mod. Opt. 44, 732-744 (1997).

M. A. Nielsen and I. L. Chuang, Quantum Computation and Quantum Information (Cambridge U. Press, 2000).

J. I. Cirac, W. Dür, B. Kraus, and M. Lewenstein, "Entangling operations and their implementation using a small amount of entanglement," Phys. Rev. Lett. 86, 544-547 (2001).

[Crossref]
[PubMed]

J. F. Poyatos, J. I. Cirac, and P. Zoller, "Complete characterization of a quantum process: the two-bit quantum gate," Phys. Rev. Lett. 78, 390-393 (1997).

[Crossref]

J. F. Clauser, M. A. Horne, A. Shimony, and R. A. Holt, "Proposed experiment to test local hidden-variable theories," Phys. Rev. Lett. 23, 880-884 (1969).

[Crossref]

M. Steffen, M. Ansmann, R. C. Bialczak, N. Katz, E. Lucero, R. McDermott, M. Neeley, E. M. Weig, A. N. Cleland, and J. M. Martinis, "Measurement of the entanglement of two superconducting qubits via state tomography," Science 313, 1423-1425 (2006).

[Crossref]
[PubMed]

V. Coffman, J. Kundu, and W. K. Wootters, "Distributed entanglement," Phys. Rev. A 61, 052306 (2000).

[Crossref]

F. De Martini, A. Mazzei, M. Ricci, and G. M. D'Ariano, "Exploiting quantum parallelism of entanglement for a complete experimental quantum characterization of a single qubit device," Phys. Rev. A 67, 062307 (2003).

[Crossref]

G. M. D'Ariano and P. L. Presti, "Imprinting a complete information about a quantum channel on its output state," Phys. Rev. Lett. 91, 047902 (2003).

[Crossref]
[PubMed]

M. Barbieri, F. De Martini, G. Di Nepi, P. Mataloni, G. M. D'Ariano, and C. Macchiavello, "Detection of entanglement with polarized photons: experimental realization of an entanglement witness," Phys. Rev. Lett. 91, 227901 (2003).

[Crossref]
[PubMed]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

M. Barbieri, F. De Martini, G. Di Nepi, P. Mataloni, G. M. D'Ariano, and C. Macchiavello, "Detection of entanglement with polarized photons: experimental realization of an entanglement witness," Phys. Rev. Lett. 91, 227901 (2003).

[Crossref]
[PubMed]

F. De Martini, A. Mazzei, M. Ricci, and G. M. D'Ariano, "Exploiting quantum parallelism of entanglement for a complete experimental quantum characterization of a single qubit device," Phys. Rev. A 67, 062307 (2003).

[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

M. Barbieri, F. De Martini, G. Di Nepi, P. Mataloni, G. M. D'Ariano, and C. Macchiavello, "Detection of entanglement with polarized photons: experimental realization of an entanglement witness," Phys. Rev. Lett. 91, 227901 (2003).

[Crossref]
[PubMed]

J. L. Dodd and M. A. Nielsen, "A simple operational interpretation of the fidelity," Phys. Rev. A 66, 044301 (2002).

[Crossref]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

A. Doherty and A. Gilchrist, Department of Physics, University of Queensland, Brisbane QLD 4072, Australia are preparing a manuscript to be called "Quantum tomography using convex optimisation."

J. I. Cirac, W. Dür, B. Kraus, and M. Lewenstein, "Entangling operations and their implementation using a small amount of entanglement," Phys. Rev. Lett. 86, 544-547 (2001).

[Crossref]
[PubMed]

A. G. White, D. F. V. James, P. H. Eberhard, and P. G. Kwiat, "Nonmaximally entangled states: production, characterization, and utilization," Phys. Rev. Lett. 83, 3103-3107 (1999).

[Crossref]

O. Gühne, P. Hyllus, D. Bruß, A. Ekert, M. Lewenstein, C. Macchiavello, and A. Sanpera, "Detection of entanglement with few local measurements," Phys. Rev. A 66, 062305 (2002).

[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

A. Gilchrist, N. K. Langford, and M. A. Nielsen, "Distance measures to compare real and ideal quantum processes," Phys. Rev. A 71, 062310 (2005).

[Crossref]

N. K. Langford, T. J. Weinhold, R. Prevedel, A. Gilchrist, J. L. O'Brien, G. J. Pryde, and A. G. White, "Demonstration of a simple entangling optical gate and its use in Bell-state analysis," Phys. Rev. Lett. 95, 210504 (2005).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

A. Doherty and A. Gilchrist, Department of Physics, University of Queensland, Brisbane QLD 4072, Australia are preparing a manuscript to be called "Quantum tomography using convex optimisation."

O. Gühne, P. Hyllus, D. Bruß, A. Ekert, M. Lewenstein, C. Macchiavello, and A. Sanpera, "Detection of entanglement with few local measurements," Phys. Rev. A 66, 062305 (2002).

[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

R. Blume-Kohout and P. Hayden, "Accurate quantum state estimation via 'Keeping the experimentalist honest'," arXiv.org e-Print archive, quantum physics/0603116, 14 March 2006, http://www.arxiv.org/abs/quant-ph/0603116.

H. F. Hofmann, "Complementary classical fidelities as an efficient criterion for the evaluation of experimentally realized quantum operations," Phys. Rev. Lett. 94, 160504 (2005).

[Crossref]
[PubMed]

H. F. Hofmann, R. Okamoto, and S. Takeuchi, "Analysis of an experimental quantum logic gate by complementary classical operations," arXiv.org e-Print archive, quantum physics/0608005, 1 August 2006, http://www.arxiv.org/abs/quant-ph/0608005.

J. F. Clauser, M. A. Horne, A. Shimony, and R. A. Holt, "Proposed experiment to test local hidden-variable theories," Phys. Rev. Lett. 23, 880-884 (1969).

[Crossref]

J. F. Clauser, M. A. Horne, A. Shimony, and R. A. Holt, "Proposed experiment to test local hidden-variable theories," Phys. Rev. Lett. 23, 880-884 (1969).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "General teleportation channel, singlet fraction, and quasidistillation," Phys. Rev. A 60, 1888-1898 (1999).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "Separability of mixed states: necessary and sufficient conditions," Phys. Lett. A 223, 1-8 (1996).

[Crossref]

B. M. Terhal and P. Horodecki, "Schmidt number for density matrices," Phys. Rev. A 61, 040301(R) (2000).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "General teleportation channel, singlet fraction, and quasidistillation," Phys. Rev. A 60, 1888-1898 (1999).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "Separability of mixed states: necessary and sufficient conditions," Phys. Lett. A 223, 1-8 (1996).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "General teleportation channel, singlet fraction, and quasidistillation," Phys. Rev. A 60, 1888-1898 (1999).

[Crossref]

M. Horodecki, P. Horodecki, and R. Horodecki, "Separability of mixed states: necessary and sufficient conditions," Phys. Lett. A 223, 1-8 (1996).

[Crossref]

O. Gühne, P. Hyllus, D. Bruß, A. Ekert, M. Lewenstein, C. Macchiavello, and A. Sanpera, "Detection of entanglement with few local measurements," Phys. Rev. A 66, 062305 (2002).

[Crossref]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

D. F. V. James, P. G. Kwiat, W. J. Munro, and A. G. White, "Measurement of qubits," Phys. Rev. A 64, 052312 (2001).

[Crossref]

A. G. White, D. F. V. James, W. J. Munro, and P. G. Kwiat, "Exploring Hilbert space: accurate characterization of quantum information," Phys. Rev. A 65, 012301 (2001).

[Crossref]

A. G. White, D. F. V. James, P. H. Eberhard, and P. G. Kwiat, "Nonmaximally entangled states: production, characterization, and utilization," Phys. Rev. Lett. 83, 3103-3107 (1999).

[Crossref]

A. Jamiolkowski, "Linear transformations which preserve trace and positive semidefiniteness of operators," Rep. Math. Phys. 3, 275-278 (1972).

[Crossref]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

M. Steffen, M. Ansmann, R. C. Bialczak, N. Katz, E. Lucero, R. McDermott, M. Neeley, E. M. Weig, A. N. Cleland, and J. M. Martinis, "Measurement of the entanglement of two superconducting qubits via state tomography," Science 313, 1423-1425 (2006).

[Crossref]
[PubMed]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
[PubMed]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
[PubMed]

M. A. Nielsen, E. Knill, and R. Laflamme, "Complete quantum teleportation using nuclear magnetic resonance," Nature 396, 52-55 (1998).

[Crossref]

J. I. Cirac, W. Dür, B. Kraus, and M. Lewenstein, "Entangling operations and their implementation using a small amount of entanglement," Phys. Rev. Lett. 86, 544-547 (2001).

[Crossref]
[PubMed]

V. Coffman, J. Kundu, and W. K. Wootters, "Distributed entanglement," Phys. Rev. A 61, 052306 (2000).

[Crossref]

N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

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[Crossref]

A. G. White, D. F. V. James, P. H. Eberhard, and P. G. Kwiat, "Nonmaximally entangled states: production, characterization, and utilization," Phys. Rev. Lett. 83, 3103-3107 (1999).

[Crossref]

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[Crossref]

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[Crossref]
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[Crossref]

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[Crossref]

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[Crossref]

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[Crossref]
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[Crossref]
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[Crossref]

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[Crossref]

W. J. Munro, K. Nemoto, and A. G. White, "The Bell inequality: a measure of entanglement?" J. Mod. Opt. 48, 1239-1246 (2001).

[Crossref]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

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[Crossref]
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[Crossref]
[PubMed]

W. J. Munro, K. Nemoto, and A. G. White, "The Bell inequality: a measure of entanglement?" J. Mod. Opt. 48, 1239-1246 (2001).

[Crossref]

A. Gilchrist, N. K. Langford, and M. A. Nielsen, "Distance measures to compare real and ideal quantum processes," Phys. Rev. A 71, 062310 (2005).

[Crossref]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

J. L. Dodd and M. A. Nielsen, "A simple operational interpretation of the fidelity," Phys. Rev. A 66, 044301 (2002).

[Crossref]

M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

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[Crossref]

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[Crossref]

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J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

N. K. Langford, T. J. Weinhold, R. Prevedel, A. Gilchrist, J. L. O'Brien, G. J. Pryde, and A. G. White, "Demonstration of a simple entangling optical gate and its use in Bell-state analysis," Phys. Rev. Lett. 95, 210504 (2005).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
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M. J. Bremner, C. M. Dawson, J. L. Dodd, A. Gilchrist, A. W. Harrow, D. Mortimer, M. A. Nielsen, and T. J. Osborne, "Practical scheme for quantum computation with any two-qubit entangling gate," Phys. Rev. Lett. 89, 247902 (2002).

[Crossref]
[PubMed]

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[Crossref]
[PubMed]

N. K. Langford, T. J. Weinhold, R. Prevedel, A. Gilchrist, J. L. O'Brien, G. J. Pryde, and A. G. White, "Demonstration of a simple entangling optical gate and its use in Bell-state analysis," Phys. Rev. Lett. 95, 210504 (2005).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

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J. L. O'Brien, G. J. Pryde, A. Gilchrist, D. F. V. James, N. K. Langford, T. C. Ralph, and A. G. White, "Quantum process tomography of a controlled-NOT gate," Phys. Rev. Lett. 93, 080502 (2004).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
[PubMed]

F. De Martini, A. Mazzei, M. Ricci, and G. M. D'Ariano, "Exploiting quantum parallelism of entanglement for a complete experimental quantum characterization of a single qubit device," Phys. Rev. A 67, 062307 (2003).

[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
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[Crossref]
[PubMed]

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[Crossref]

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

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[Crossref]
[PubMed]

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[Crossref]

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[Crossref]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
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J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

N. A. Peters, J. B. Altepeter, D. A. Branning, E. R. Jeffrey, T.-C. Wei, and P. G. Kwiat, "Maximally entangled mixed states: creation and concentration," Phys. Rev. Lett. 92, 133601 (2004).

[Crossref]
[PubMed]

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[Crossref]
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[Crossref]
[PubMed]

N. K. Langford, T. J. Weinhold, R. Prevedel, A. Gilchrist, J. L. O'Brien, G. J. Pryde, and A. G. White, "Demonstration of a simple entangling optical gate and its use in Bell-state analysis," Phys. Rev. Lett. 95, 210504 (2005).

[Crossref]
[PubMed]

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[Crossref]
[PubMed]

J. B. Altepeter, D. Branning, E. Jeffrey, T. C. Wei, P. G. Kwiat, R. T. Thew, J. L. OBrien, M. A. Nielsen, and A. G. White, "Ancilla-assisted quantum process tomography," Phys. Rev. Lett. 93, 193601 (2003).

[Crossref]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
[PubMed]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

W. J. Munro, K. Nemoto, and A. G. White, "The Bell inequality: a measure of entanglement?" J. Mod. Opt. 48, 1239-1246 (2001).

[Crossref]

D. F. V. James, P. G. Kwiat, W. J. Munro, and A. G. White, "Measurement of qubits," Phys. Rev. A 64, 052312 (2001).

[Crossref]

A. G. White, D. F. V. James, W. J. Munro, and P. G. Kwiat, "Exploring Hilbert space: accurate characterization of quantum information," Phys. Rev. A 65, 012301 (2001).

[Crossref]

A. G. White, D. F. V. James, P. H. Eberhard, and P. G. Kwiat, "Nonmaximally entangled states: production, characterization, and utilization," Phys. Rev. Lett. 83, 3103-3107 (1999).

[Crossref]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

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[Crossref]

W. J. Munro, K. Nemoto, and A. G. White, "The Bell inequality: a measure of entanglement?" J. Mod. Opt. 48, 1239-1246 (2001).

[Crossref]

I. L. Chuang and M. A. Nielsen, "Prescription for experimental determination of the dynamics of a quantum black box," J. Mod. Opt. 44, 732-744 (1997).

F. Schmidt-Kaler, H. Häffner, M. Riebe, S. Gulde, G. P. T. Lancaster, T. Deuschle, C. Becher, C. F. Roos, J. Eschner, and R. Blatt, "Realization of the Cirac-Zoller controlled-NOT quantum gate," Nature 422, 408-411 (2003).

[Crossref]
[PubMed]

J. L. O'Brien, G. J. Pryde, A. G. White, T. C. Ralph, and D. Branning, "Demonstration of an all-optical quantum controlled-NOT gate," Nature 426, 264-267 (2003).

[Crossref]
[PubMed]

C. A. Sackett, D. Kielpinski, B. E. King, C. Langer, V. Meyer, C. J. Myatt, M. Rowe, Q. A. Turchette, W. M. Itano, D. J. Wineland, and C. Monroe, "Experimental entanglement of four particles," Nature 404, 256-259 (2000).

[Crossref]
[PubMed]

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[Crossref]

M. A. Nielsen, "A simple formula for the average gate fidelity of a quantum dynamical operation," Phys. Lett. A 303, 249-252 (2002).

[Crossref]

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[Crossref]

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[Crossref]

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[Crossref]

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[Crossref]

A. Gilchrist, N. K. Langford, and M. A. Nielsen, "Distance measures to compare real and ideal quantum processes," Phys. Rev. A 71, 062310 (2005).

[Crossref]

J. L. Dodd and M. A. Nielsen, "A simple operational interpretation of the fidelity," Phys. Rev. A 66, 044301 (2002).

[Crossref]

V. Coffman, J. Kundu, and W. K. Wootters, "Distributed entanglement," Phys. Rev. A 61, 052306 (2000).

[Crossref]

W. J. Munro, D. F. V. James, A. G. White, and P. G. Kwiat, "Maximizing the entanglement of two mixed qubits," Phys. Rev. A 64, 030302 (2001).

[Crossref]

D. F. V. James, P. G. Kwiat, W. J. Munro, and A. G. White, "Measurement of qubits," Phys. Rev. A 64, 052312 (2001).

[Crossref]

A. G. White, D. F. V. James, W. J. Munro, and P. G. Kwiat, "Exploring Hilbert space: accurate characterization of quantum information," Phys. Rev. A 65, 012301 (2001).

[Crossref]

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[Crossref]

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[Crossref]
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[Crossref]
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On the qubit characteristic sphere the equal-weight superpositions form a great circle midway between the logical states. For example, on the Bloch sphere they lie on the equator, which can be accessed with π/2 pulses; on the Poincaré sphere they lie on the great circle containing the diagonally and circularly polarized states.

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Note that an operator sum representation is not unique and that there is unitary freedom in its choice.

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