Typical elements of quantum networks are made by identical systems, which are the basic particles constituting a resource for quantum information processing. Whether the indistinguishability due to particle identity is an exploitable quantum resource remains an open issue. Here we study independently prepared identical particles showing that, when they spatially overlap, an operational entanglement exists that can be made manifest by means of separated localized measurements. We prove this entanglement is physical in that it can be directly exploited to activate quantum information protocols, such as teleportation. These results establish that particle indistinguishability is a utilizable quantum feature and open the way to new quantum-enhanced applications.
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http://dx.doi.org/10.1103/PhysRevLett.120.240403 | DOI Listing |
Sci Adv
January 2025
Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, PR China.
Quantum simulators with hundreds of qubits and engineerable Hamiltonians have the potential to explore quantum many-body models that are intractable for classical computers. However, learning the simulated Hamiltonian, a prerequisite for any quantitative applications of a quantum simulator, remains an outstanding challenge due to the fast increasing time cost with the qubit number and the lack of high-fidelity universal gate operations in the noisy intermediate-scale quantum era. Here, we demonstrate the Hamiltonian learning of a two-dimensional ion trap quantum simulator with 300 qubits.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Ens de Lyon, Université Lyon, CNRS, Laboratoire de Physique, F-69342 Lyon, France.
We introduce a new paradigm for the preparation of deeply entangled states useful for quantum metrology. We show that, when the quantum state is an eigenstate of an operator A, observables G which are completely off diagonal with respect to A have purely quantum fluctuations, as quantified by the quantum Fisher information, namely, F_{Q}(G)=4⟨G^{2}⟩. This property holds regardless of the purity of the quantum state, and it implies that off-diagonal fluctuations represent a metrological resource for phase estimation.
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December 2024
Universidade Federal de Pernambuco, Departamento de Física, Centro de Ciências Exatas e da Natureza, Recife, Pernambuco 50670-901 Brazil.
We introduce and explore the notion of texture of an arbitrary quantum state, in a selected basis. In the first part of this Letter we develop a resource theory and show that state texture is adequately described by an easily computable monotone, which is also directly measurable. It is shown that textures are useful in the characterization of unknown quantum gates in universal circuit layers.
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December 2024
Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Cité, CNRS UMR 7162, 75013 Paris, France.
We present a method to systematically identify and classify quantum optical nonclassical states as classical or nonclassical based on the resources they create on a bosonic quantum computer. This is achieved by converting arbitrary bosonic states into multiple modes, each occupied by a single photon, thereby defining qubits of a bosonic quantum computer. Starting from a bosonic classical-like state in a representation that explicitly respects particle number superselection rules, we apply universal gates to create arbitrary superpositions of states with the same total particle number.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Tel Aviv University, School of Physics and Astronomy, Tel Aviv 6997801, Israel.
Measurement-based quantum computation (MBQC) is a universal platform to realize unitary gates, only using measurements that act on a preprepared entangled resource state. By deforming the measurement bases, as well as the geometry of the resource state, we show that MBQC circuits always transmit and act on the input state but generally realize nonunitary logical gates. In contrast to the stabilizer formalism that is often used for unitary gates, we find that ZX-calculus is an ideal computation method for these nonunitary gates.
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