Search results for "Entanglement"
showing 10 items of 371 documents
The physical origin of a photon-number parity effect in cavity quantum electrodynamics
2021
Abstract The rapidly increasing capability to modulate the physicochemical properties of atomic groups and molecules by means of their coupling to radiation, as well as the revolutionary potential of quantum computing for materials simulation and prediction, fuel the interest for non-classical phenomena produced by atom-radiation interaction in confined space. One of such phenomena is a “parity effect” that arises in the dynamics of an atom coupled to two degenerate cavity field modes by two-photon processes and manifests itself as a strong dependence of the field dynamics on the parity of the initial number of photons. Here we identify the physical origin of this effect in the quantum corr…
Diffusion and transfer of entanglement in an array of inductively coupled flux qubits
2007
A theoretical scheme to generate multipartite entangled states in a Josephson planar-designed architecture is reported. This scheme improves the one published in [Phys. Rev. B 74, 104503 (2006)] since it speeds up the generation of W entangled states in an MxN array of inductively coupled Josephson flux qubits by reducing the number of necessary steps. In addition, the same protocol is shown to be able to transfer the W state from one row to the other.
High-dimensional one-way quantum processing implemented on d-level cluster states
2019
Taking advantage of quantum mechanics for executing computational tasks faster than classical computers1 or performing measurements with precision exceeding the classical limit2,3 requires the generation of specific large and complex quantum states. In this context, cluster states4 are particularly interesting because they can enable the realization of universal quantum computers by means of a ‘one-way’ scheme5, where processing is performed through measurements6. The generation of cluster states based on sub-systems that have more than two dimensions, d-level cluster states, provides increased quantum resources while keeping the number of parties constant7, and also enables novel algorithm…
Holographic encoding of universality in corner spectra
2017
In numerical simulations of classical and quantum lattice systems, 2d corner transfer matrices (CTMs) and 3d corner tensors (CTs) are a useful tool to compute approximate contractions of infinite-size tensor networks. In this paper we show how the numerical CTMs and CTs can be used, {\it additionally\/}, to extract universal information from their spectra. We provide examples of this for classical and quantum systems, in 1d, 2d and 3d. Our results provide, in particular, practical evidence for a wide variety of models of the correspondence between $d$-dimensional quantum and $(d+1)$-dimensional classical spin systems. We show also how corner properties can be used to pinpoint quantum phase …
Feel the force
2014
An approach based on quantum sensing, in which controlled quantum systems serve as precision sensors, has enabled measurement of the weak magnetic interaction between two electrons bound to two separate ions. See Letter p.376 Every electron carries an intrinsic magnetic dipole moment, so any two electrons should therefore exert magnetic forces on one another. The forces involved are very small, and at atomic scale Coulomb interaction is dominant, so it is extremely difficult to observe the magnetic interaction. However, Shlomi Kotler et al. have now done just that, measuring the interaction between two electrons, in separate trapped strontium-88 ions. The two electrons exhibit spin entangle…
Discrete symmetries with neutral mesons
2018
Symmetries, and Symmetry Breakings, in the Laws of Physics play a crucial role in Fundamental Science. Parity and Charge Conjugation Violations prompted the consideration of Chiral Fields in the construction of the Standard Model, whereas CP-Violation needed at least three families of Quarks leading to Flavour Physics. In this Lecture I discuss the Conceptual Basis and the present experimental results for a Direct Evidence of Separate Reversal-in-Time T, CP and CPT Genuine Asymmetries in Decaying Particles like Neutral Meson Transitions, using Quantum Entanglement and the Decay as a Filtering Measurement. The eight transitions associated to the Flavour-CP eigenstate decay products of entang…
Dynamical quantum repeater using cavity-QED and optical coherent states
2013
In the framework of cavity QED, we propose a quantum repeater scheme that uses coherent light and atoms coupled to optical cavities. In contrast to conventional schemes, we exploit solely the cavity QED evolution for the entire quantum repeater scheme and, thus, avoid any explicit execution of quantum logical gates. The entanglement distribution between the repeater nodes is realized with the help of pulses of coherent light interacting with the atom-cavity system in each repeater node. In our previous paper [D. Gonta and P. van Loock, Phys. Rev. A 86, 052312 (2012)], we already proposed a dynamical protocol to purify a bipartite entangled state using the evolution of atomic chains coupled …
Hybrid quantum repeater for qudits
2017
We present a "hybrid quantum repeater" protocol for the long-distance distribution of atomic entangled states beyond qubits. In our scheme, imperfect noisy entangled pairs of two qudits, i.e., two discrete-variable $d$-level systems, each of, in principle, arbitrary dimension $d$, are initially shared between the intermediate stations of the channel. This is achieved via local, sufficiently strong light-matter interactions, involving optical coherent states and their transmission after these interactions, and optical measurements on the transmitted field modes, especially (but not restricted to) efficient continuous-variable homodyne detections ("hybrid" here refers to the simultaneous expl…
Long-Time Preservation of Nonlocal Entanglement
2009
We investigate how nonlocal entanglement, as identified by violations of a Bell inequality, may be preserved during the evolution. Our system consists of two qubits each embedded in a zero-temperature bosonic reservoir evolving independently and initially in an entangled mixed state. We show that the violation of the Bell inequality can be related to the single-qubit population of excited state in such a way that, by appropriately choosing structured environments that give rise to sufficiently high values of population trapping, long-time preservation of nonlocal entanglement can be correspondingly achieved.
Intraenvironmental correlations in the ground state of a nonisolated two-state particle
1996
The existence of entanglement in the ground state of a two-level particle coupled to a bosonic environment is proved. The quantum covariances of pairs of simple dynamical variables relative to different subsystems are explicitly shown to be bounded. Physically interpretable conditions for the occurrence of weak intraenvironmental correlations are reported and discussed. The potentialities of our treatment are briefly put into evidence.