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We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas, such that the fidelity of all copies may be different. We show that the optimal asymmetric Gaussian cloning can be performed…

Quantum Physics · Physics 2009-11-13 Jaromir Fiurasek , Nicolas J. Cerf

We investigate several classes of state-dependent quantum cloners for three-level systems. These cloners optimally duplicate some of the four maximally-conjugate bases with an equal fidelity, thereby extending the phase-covariant qubit…

Quantum Physics · Physics 2009-11-07 Nicolas J. Cerf , Thomas Durt , Nicolas Gisin

We theoretically and experimentally investigate conditional enhancement of overall coherence of quantum states by probabilistic quantum operations that apply to the input state a quantum filter diagonal in the basis of incoherent states. We…

Quantum Physics · Physics 2021-08-03 Robert Stárek , Michal Mičuda , Michal Kolář , Radim Filip , Jaromír Fiurášek

The fundamental question of how to best simulate quantum systems using conventional computational resources lies at the forefront of condensed matter and quantum computation. It impacts both our understanding of quantum materials and our…

Strongly Correlated Electrons · Physics 2021-09-29 Juan Carrasquilla , Di Luo , Felipe Pérez , Ashley Milsted , Bryan K. Clark , Maksims Volkovs , Leandro Aolita

We propose a scalable and robust architecture for one-way quantum computation using coupled networks of superconducting transmission line resonators. In our protocol, quantum information is encoded into the long-lived photon states of the…

Quantum Physics · Physics 2015-06-03 Chun-Wang Wu , Ming Gao , Hong-Yi Li , Zhi-Jiao Deng , Hong-Yi Dai , Ping-Xing Chen , Cheng-Zu Li

The characterization of a quantum device is a crucial step in the development of quantum experiments. This is accomplished via Quantum Process Tomography, which combines the outcomes of different projective measurements to deliver a…

Quantum Physics · Physics 2025-06-26 Francesco Di Colandrea , Nazanin Dehghan , Alessio D'Errico , Ebrahim Karimi

Modelling of photonic devices traditionally involves solving the equations of light-matter interaction and light propagation, and it is restrained by their applicability. Here we demonstrate an alternative modelling methodology by creating…

Quantum Physics · Physics 2024-11-21 Anton N. Vetlugin , Cesare Soci , Nikolay I. Zheludev

Compilation optimizes quantum algorithms performances on real-world quantum computers. To date, it is performed via classical optimization strategies. We introduce a class of quantum algorithms to perform compilation via quantum computers,…

Quantum Physics · Physics 2025-09-25 Davide Rattacaso , Daniel Jaschke , Marco Ballarin , Ilaria Siloi , Simone Montangero

The information encoded in the polarization of a single photon can be transferred to a remote location by two-channel continuous-variable quantum teleportation. However, the finite entanglement used in the teleportation causes random…

Quantum Physics · Physics 2009-11-13 Toshiki Ide , Holger F. Hofmann

Quantum tomography is an essential method of the photonic technology toolbox and is routinely used for evaluation of experimentally prepared states of light and characterization of devices transforming such states. The tomography procedure…

Quantum Physics · Physics 2018-12-18 Radim Hošák , Robert Stárek , Miroslav Ježek

We investigate the problem of copying pure two-qubit states of a given degree of entanglement in an optimal way. Completely positive covariant quantum operations are constructed which maximize the fidelity of the output states with respect…

Quantum Physics · Physics 2009-11-10 J. Novotny , G. Alber , I. Jex

Four-qubit cluster states of two photons entangled in polarization and linear momentum have been used to realize a complete set of single qubit rotations and the C-NOT gate for equatorial qubits with high values of fidelity. By the…

Quantum Physics · Physics 2015-05-13 Giuseppe Vallone , Enrico Pomarico , Francesco De Martini , Paolo Mataloni

Partial tomography, which focuses on reconstructing reduced density matrices (RDMs), has emerged as a promising approach for characterizing complex quantum systems, particularly when full state tomography is impractical. Recently,…

Quantum Physics · Physics 2024-10-18 Chao Wei , Tao Xin

Quantum information systems are on a path to vastly exceed the complexity of any classical device. The number of entangled qubits in quantum devices is rapidly increasing and the information required to fully describe these systems scales…

All quantum information processes inevitably requires the explicit state preparation of an entangled state. Here we present the construction of a quantum switchboard which can act both as an optimal quantum cloning machine and a quantum…

Quantum Physics · Physics 2007-05-23 D. Kaszlikowski , L. C. Kwek , C. H. Lai , V. Vedral

Multiphoton state in quantum cryptography decreases its security. Key disclosing with universal quantum cloning machine (UQCM) is considered in explicit manner. Although UQCM cannot make perfect clones, there is some invariant quantity…

Quantum Physics · Physics 2007-05-23 Tsuyoshi Nishioka , Toshio Hasegawa , Hirokazu Ishizuka

We consider quantum-information division, which is characterized by a channel whose outputs have no correlation and are not completely randomized. We show that the quantum-information division is possible in a probabilistic manner by…

Quantum Physics · Physics 2014-04-02 Yuji Sekino , Satoshi Ishizaka

The performance of quantum algorithms for ground-state energy estimation is directly impacted by the quality of the initial state, where quality is traditionally defined in terms of the overlap of the input state with the target state. An…

It is shown that any quantum operation that perfectly clones the entanglement of all maximally-entangled qubit pairs cannot preserve separability. This ``entanglement no-cloning'' principle naturally suggests that some approximate cloning…

Quantum Physics · Physics 2009-11-10 Louis-Philippe Lamoureux , Patrick Navez , Jaromir Fiurasek , Nicolas J. Cerf

Quantum mechanics put restriction on performing some task which we can do classically. One such restriction is that we cannot copy an arbitrary quantum state. This is known as No-cloning theorem. Although quantum mechanics forbid us to…

Quantum Physics · Physics 2009-02-11 Satyabrata Adhikari