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21 p, 1.4 MB |
Probabilistic metrology or how some measurement outcomes render ultra-precise estimates
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Calsamiglia Costa, John (Universitat Autònoma de Barcelona. Departament de Física) ;
Gendra Casalí, Bernat (Universitat Autònoma de Barcelona. Departament de Física) ;
Muñoz Tapia, Ramon (Universitat Autònoma de Barcelona. Departament de Física) ;
Bagán Capella, Emili (Universitat Autònoma de Barcelona. Departament de Física)
We show on theoretical grounds that, even in the presence of noise, probabilistic measurement strategies (which have a certain probability of failure or abstention) can provide, upon a heralded successful outcome, estimates with a precision that exceeds the deterministic bounds for the average precision. [...]
2016 - 10.1088/1367-2630/18/10/103049
New journal of physics, Vol. 18 (October 2016) , art. 103049
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22 p, 562.0 KB |
Unsupervised classification of quantum data
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Sentís Herrera, Gael (Universität Siegen. Naturwissenschaftlich-Technische Fakultät) ;
Monras Blasi, Àlex (Universitat Autònoma de Barcelona. Departament de Física) ;
Muñoz Tapia, Ramon (Universitat Autònoma de Barcelona. Departament de Física) ;
Calsamiglia Costa, John (Universitat Autònoma de Barcelona. Departament de Física) ;
Bagán Capella, Emili (Universitat Autònoma de Barcelona. Departament de Física)
We introduce the problem of unsupervised classification of quantum data, namely, of systems whose quantum states are unknown. We derive the optimal single-shot protocol for the binary case, where the states in a disordered input array are of two types. [...]
2019 - 10.1103/PhysRevX.9.041029
Physical Review, Vol. 9 Núm. art. 041029 (2019)
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17 p, 934.7 KB |
Beating noise with abstention in state estimation
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Gendra Casalí, Bernat (Universitat Autònoma de Barcelona. Departament de Física) ;
Ronco Bonvehi, Elio (Universitat Autònoma de Barcelona. Departament de Física) ;
Calsamiglia Costa, John (Universitat Autònoma de Barcelona. Departament de Física) ;
Muñoz Tapia, Ramon (Universitat Autònoma de Barcelona. Departament de Física) ;
Bagán Capella, Emili (Universitat Autònoma de Barcelona. Departament de Física)
We address the problem of estimating pure qubit states with nonideal (noisy) measurements in the multiple-copy scenario, where the data consist of a number N of identically prepared qubits. We show that the average fidelity of the estimates can increase significantly if the estimation protocol allows for inconclusive answers, or abstentions. [...]
2012 - 10.1088/1367-2630/14/10/105015
New journal of physics, Vol. 14 (October 2012) , art. 105015
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12 p, 253.3 KB |
Estimation of quantum finite mixtures
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de Vicente Majúa, Julio Íñigo (Universitat Autònoma de Barcelona. Departament de Física) ;
Calsamiglia Costa, John (Universitat Autònoma de Barcelona. Departament de Física) ;
Muñoz Tapia, Ramon (Universitat Autònoma de Barcelona. Departament de Física) ;
Bagán Capella, Emili (Universitat Autònoma de Barcelona. Departament de Física) ;
American Physical Society
We consider the problem of determining the weights of a quantum ensemble. That is to say, given a quantum system that is in a set of possible known states according to an unknown probability law, we give strategies to estimate the individual probabilities, weights, or mixing proportions. [...]
2010 - 10.1103/PhysRevA.81.012332
Physical review. A, Vol. 81, Issue 1 (January 2010) , p. 012332-1-012332-12
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