Scalable estimation of pure multi-qubit states

2022-09-19T15:57:15+02:00Tags: , , , , |

Authors: Pereira, Luciano; Zambrano, Leonardo; Delgado, Aldo Journal: NPJ QUANTUM INFORMATION Publication date: 2022/05/13 DOI: 10.1038/s41534-022-00565-9 Abstract: We introduce an inductive n-qubit pure-state estimation method based on projective measurements on mn + 1 separable bases or m entangled bases plus the computational basis, with m >= 2. The method exhibits a favorable scaling in the [...]

Critical quantum metrology with fully-connected models: from Heisenberg to Kibble-Zurek scaling

2022-09-19T15:57:11+02:00Tags: , |

Authors: Garbe, Louis; Abah, Obinna; Felicetti, Simone; Puebla, Ricardo Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2022/06/15 DOI: 10.1088/2058-9565/ac6ca5 Abstract: Phase transitions represent a compelling tool for classical and quantum sensing applications. It has been demonstrated that quantum sensors can in principle saturate the Heisenberg scaling, the ultimate precision bound allowed by quantum mechanics, in [...]

Spin Many-Body Phases in Standard- and Topological-Waveguide QED Simulators

2022-09-19T15:57:06+02:00Tags: , , |

Authors: Bello, M.; Platero, G.; Gonzalez-Tudela, A. Journal: PRX QUANTUM Publication date: 2022/03/07 DOI: 10.1103/PRXQuantum.3.010336 Abstract: Waveguide QED has emerged as a powerful analog quantum simulator due to the possibility of mediating versatile spin-spin interactions with tunable sign, range, and even dimerization. Yet, despite their potential, the many-body phases emerging from these systems have only [...]

Visualizing the emission of a single photon with frequency and time resolved spectroscopy

2022-04-05T17:41:04+02:00Tags: , |

Authors: Sharafiev, Aleksei; Juan, Mathieu L.; Gargiulo, Oscar; Zanner, Maximilian; Woegerer, Stephanie; Garcia-Ripoll, Juan Jose; Kirchmair, Gerhard Journal: QUANTUM Publication date: 2021/06/10 DOI: 10.22331/q-2021-06-10-474 Abstract: At the dawn of Quantum Physics, Wigner and Weisskopf obtained a full analytical description (a photon portrait) of the emission of a single photon by a twolevel system, using the [...]

Frequency-resolved photon correlations in cavity optomechanics

2022-04-05T17:41:03+02:00Tags: , |

Authors: Schmidt, M. K.; Esteban, R.; Giedke, G.; Aizpurua, J.; Gonzalez-Tudela, A. Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2021/07/01 DOI: 10.1088/2058-9565/abe569 Abstract: Frequency-resolved photon correlations have proven to be a useful resource to unveil nonlinearities hidden in standard observables such as the spectrum or the standard (color-blind) photon correlations. In this manuscript, we analyze [...]

Hybrid quantum-classical optimization with cardinality constraints and applications to finance

2022-04-05T17:41:01+02:00Tags: , |

Authors: Fernandez-Lorenzo, Samuel; Porras, Diego; Garcia-Ripoll, Juan Jose Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2021/07/01 DOI: 10.1088/2058-9565/abf9af Abstract: In this work we develop tools to address combinatorial optimization problems with a cardinality constraint, in which only a subset of variables end up having nonzero values. Firstly, we introduce a new heuristic pruning method that [...]

Non-equilibrium coupling of a quartz resonator to ions for Penning-trap fast resonant detection

2022-04-05T17:40:55+02:00Tags: , |

Authors: Berrocal, Joaquin; Lohse, Steffen; Dominguez, Francisco; Gutierrez, Manuel J.; Fernandez, Francisco J.; Block, Michael; Garcia-Ripoll, Juan J.; Rodriguez, Daniel Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2021/10/01 DOI: 10.1088/2058-9565/ac01bc Abstract: The coherent coupling between a quartz electro-mechanical resonator at room temperature and trapped ions in a 7 T Penning trap has been demonstrated for [...]

Automatic design of quantum feature maps

2022-04-05T17:40:55+02:00Tags: , |

Authors: Altares-Lopez, Sergio; Ribeiro, Angela; Garcia-Ripoll, Juan Jose Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2021/10/01 DOI: 10.1088/2058-9565/ac1ab1 Abstract: We propose a new technique for the automatic generation of optimal ad-hoc ansatze for classification by using quantum support vector machine. This efficient method is based on non-sorted genetic algorithm II multiobjective genetic algorithms which allow [...]

Frequency-resolved photon correlations in cavity optomechanics

2021-10-28T11:16:34+02:00Tags: , |

Authors: Schmidt, M. K.; Esteban, R.; Giedke, G.; Aizpurua, J.; Gonzalez-Tudela, A. Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2021/06/11 DOI: 10.1088/2058-9565/abe569 Abstract: Frequency-resolved photon correlations have proven to be a useful resource to unveil nonlinearities hidden in standard observables such as the spectrum or the standard (color-blind) photon correlations. In this manuscript, we analyze [...]

Multimode Fock states with large photon number: effective descriptions and applications in quantum metrology

2021-02-12T10:08:13+01:00Tags: , |

Authors: Perarnau-Llobet, M.; Gonzalez-Tudela, A.; Cirac, J., I Contribution: Article Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2020/03/01 DOI: 10.1088/2058-9565/ab6ce5 Abstract: We develop general tools to characterise and efficiently compute relevant observables of multimode N-photon states generated in nonlinear decays in one-dimensional waveguides. We then consider optical interferometry in a Mach-Zender interferometer where a d-mode photonic [...]

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