Minimal orthonormal bases for pure quantum state estimation

2024-03-27T14:34:45+01:00Tags: , |

Authors: Zambrano, Leonardo; Pereira, Luciano; Delgado, Aldo Journal: QUANTUM Publication date: 2024/02/08 DOI: Abstract: We present an analytical method to estimate pure quantum states using a minimum of three measurement bases in any finite -dimensional Hilbert space. This is optimal as two bases are insufficient to construct an informationally complete positive operator -valued measurement (ICPOVM) [...]

Parallel tomography of quantum non-demolition measurements in multi-qubit devices

2024-03-27T13:58:19+01:00Tags: , , , , |

Authors: Pereira, L.; Garcia-Ripoll, J. J.; Ramos, T. Journal: NPJ QUANTUM INFORMATION Publication date: 2023/03/04 DOI: 10.1038/s41534-023-00688-7 Abstract: An efficient characterization of QND measurements is an important ingredient toward certifying and improving the performance and scalability of quantum processors. In this work, we introduce a parallel tomography of QND measurements that addresses single- and two-qubit [...]

Improving quantum state transfer: correcting non-Markovian and distortion effects

2024-03-27T13:58:18+01:00Tags: , |

Authors: Peñas, Guillermo F.; Puebla, Ricardo; Garcia-Ripoll, Juan Jose Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2023/10/01 DOI: 10.1088/2058-9565/acf60a Abstract: Quantum state transfer is a key operation for quantum information processing. The original pitch-and-catch protocols rely on flying qubits or single photons with engineered wavepacket shapes to achieve a deterministic, fast and high-fidelity transfer. Yet, [...]

Driven-dissipative topological phases in parametric resonator arrays

2024-03-27T13:57:45+01:00Tags: , |

Authors: Gomez-Leon, Alvaro; Ramos, Tomas; Gonzalez-Tudela, Alejandro; Porras, Diego Journal: QUANTUM Publication date: 2023/05/23 DOI: Abstract: We study the phenomena of topological amplification in arrays of parametric oscillators. We find two phases of topological amplification, both with directional transport and exponential gain with the number of sites, and one of them featuring squeezing. We also [...]

Quantum control of tunable-coupling transmons using dynamical invariants of motion

2024-03-27T13:57:38+01:00Tags: , |

Authors: Espinos, H.; Panadero, I; Garcia-Ripoll, J. J.; Torrontegui, E. Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2023/04/01 DOI: 10.1088/2058-9565/acbed7 Abstract: We analyze the implementation of a fast nonadiabatic CZ gate between two transmon qubits with tunable coupling. The gate control method is based on a theory of dynamical invariants which leads to reduced leakage [...]

Multiobjective variational quantum optimization for constrained problems: an application to cash handling

2024-03-27T13:57:34+01:00Tags: , |

Authors: Diez-Valle, Pablo; Luis-Hita, Jorge; Hernandez-Santana, Senaida; Martinez-Garcia, Fernando; Diaz-Fernandez, Alvaro; Andres, Eva; Garcia-Ripoll, Juan Jose; Sanchez-Martinez, Escolastico; Porras, Diego Journal: QUANTUM SCIENCE AND TECHNOLOGY Publication date: 2023/10/01 DOI: 10.1088/2058-9565/ace474 Abstract: Combinatorial optimization problems are ubiquitous in industry. In addition to finding a solution with minimum cost, problems of high relevance involve a number of [...]

Detecting entanglement of unknown states by violating the Clauser-Horne-Shimony-Holt inequality

2024-03-27T13:57:25+01:00Tags: , , |

Authors: Cortes-Vega, J.; Barra, J. F.; Pereira, L.; Delgado, A. Journal: QUANTUM INFORMATION PROCESSING Publication date: 2023/05/09 DOI: 10.1007/s11128-023-03953-y Abstract: Entangled states play a fundamental role in quantum mechanics and are at the core of many contemporary applications, such as quantum communication and quantum computing. Therefore, determining whether a state is entangled or not is [...]

Waveguide QED with Quadratic Light-Matter Interactions

2024-03-27T13:57:03+01:00Tags: , , |

Authors: Alushi, Uesli; Ramos, Tomas; Garcia-Ripoll, Juan Jose; Di Candia, Roberto; Felicetti, Simone Journal: PRX QUANTUM Publication date: 2023/08/25 DOI: 10.1103/PRXQuantum.4.030326 Abstract: Quadratic light-matter interactions are nonlinear couplings such that quantum emitters interact with photonic or phononic modes exclusively via the exchange of excitation pairs. Implementable with atomic and solid-state systems, these couplings lead to [...]

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

2023-02-21T13:37:09+01:00Tags: , , |

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 [...]

Scalable estimation of pure multi-qubit states

2023-02-21T13:36:54+01:00Tags: , , , , |

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 [...]

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