Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0801.2184 · Physical Review Letters

Bell Inequality Violation with Two Remote Atomic Qubits

Dzmitry Matsukevich, Peter Maunz, David L. Moehring, Steven Olmschenk, Christopher R. Monroe

Published Apr 18, 2008• 392 citations
arXivHTMLPDF

Abstract

We observe violation of a Bell inequality between the quantum states of two remote Yb+ ions separated by a distance of about 1 m with the detection loophole closed. The heralded entanglement of two ions is established via interference and joint detection of two emitted photons, whose polarization is entangled with each ion. The entanglement of remote qubits is also characterized by full quantum state tomography.

DOI
10.1103/physrevlett.100.150404

Related papers

Robust Long-Distance Entanglement and a Loophole-Free Bell Test with Ions and Photons

Christoph Simon, William T. M. Irvine

Two trapped ions that are kilometers apart can be entangled by the joint detection of two photons, each coming from one of the ions, in a basis of entangled states. Such a detection is possible with linear optical elements. The use of two-photon interference allows entanglement distribution free of interferometric sensitivity to the path length of the photons. The present method of creating entangled ions also opens up the possibility of a loophole-free test of Bell's inequalities.

arXiv:quant-ph/0303023•Physical Review Letters•Sep 12, 2003•357 citations

Ion–photon entanglement and Bell inequality violation with ^138Ba^+

Carolyn Auchter, Chen-Kuan Chou, Thomas W. Noel +1 more

We report on the demonstration of ion–photon entanglement and Bell inequality violation in a system of trapped Ba138+ ions. Entanglement between the Zeeman sublevels of the ground state of a single Ba138+ ion and the polarization state of a single 493 nm photon emitted by the ion with a fidelity of 0.84±0.01 was achieved, along with a Bell signal of 2.3, exceeding the classical limit of 2 by more than eight standard deviations. This system is a promising candidate for a loophole-free Bell inequality violation test using long-range ion–ion entanglement as the wavelengths of the transitions of Ba138+ are in the visible region and thus suitable for long-range transmission over fiber optic cable.

arXiv:1310.0028•Journal of the Optical Society of America B•Jun 12, 2014•17 citations

From loophole-free violation of Bell's inequality toward device-independent quantum communication protocols

Kai Redeker, Daniel Burchardt, Robert Garthoff +2 more

Summary form only given. Here we present our experiment using heralded entanglement between two 87Rb-atoms separated by 400 m violating Bell's inequality [1]. First each atom is entangled with a photon, which is coupled into single-mode fiber. The interference of the two photons at a beam splitter enables one to project the state onto a Bell state, which leaves the atoms in an entangled state [2]. For space-like separation, the state measurements on the two atoms together with the random choice of the measurement basis, have to be performed in a time shorter than 1.33μs. The atomic state readout itself is based on a highly efficient state-selective ionization and subsequent detection of the ionization fragments by channel-electron-multipliers (CEM) [3]. Altogether the time for the state readout is below 1μs and the locality condition is fulfilled. Evaluation of 5000 events for each of two entangled atom-atom states shows a significant violation of Bell's inequality with S-parameters of 2.240 ± 0.047 and 2.204 ± 0.047.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2017•0 citations

Towards a Loophole-Free Test of Bell's Inequality with Entangled Pairs of Neutral Atoms

Wenjamin Rosenfeld, Markus Weber, Jürgen Volz +5 more

Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of atoms). In order to constitute conclusive evidence, two conditions have to be satisfied. First, strict separation of the measurement events in the sense of special relativity is required ("locality loophole"). Second, almost all entangled pairs have to be detected (for particles in a maximally entangled state the required detector efficiency is 82.8%), which is hard to achieve experimentally ("detection loophole"). By using the recently demonstrated entanglement between single trapped atoms and single photons it becomes possible to entangle two atoms at a large distance via entanglement swapping. Combining the high detection efficiency achieved with atoms with the space-like separation of the atomic state detection events, both loopholes can be closed within the same experiment. In this paper we present estimations based on current experimental achievements which show that such an experiment is feasible in future.

arXiv:0906.0703•Advanced Science Letters•Dec 1, 2009•38 citations

Towards a Loophole-Free Test of Bell's Inequality with Entangled Pairs of Neutral Atoms

Rosenfeld, W., Weber, M., Jürgen Volz +5 more

Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of atoms). In order to constitute conclusive evidence, two conditions have to be satisfied. First, strict separation of the measurement events in the sense of special relativity is required ("locality loophole"). Second, almost all entangled pairs have to be detected (for particles in a maximally entangled state the required detector efficiency is 82.8%), which is hard to achieve experimentally ("detection loophole"). By using the recently demonstrated entanglement between single trapped atoms and single photons it becomes possible to entangle two atoms at a large distance via entanglement swapping. Combining the high detection efficiency achieved with atoms with the space-like separation of the atomic state detection events, both loopholes can be closed within the same experiment. In this paper we present estimations based on current experimental achievements which show that such an experiment is feasible in future.

•Dec 1, 2009•29 citations

Entanglement of Trapped-Ion Qubits Separated by 230 Meters

Victor L. Krutyanskiy, Maria Galli, Vojtech Krcmarsky +13 more

We report on an elementary quantum network of two atomic ions separated by 230 m. The ions are trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion is entangled with the polarization state of a single cavity photon; subsequent to interference of the photons at a beam splitter, photon detection heralds entanglement between the two ions. Fidelities of up to (88.0+2.2-4.7)% are achieved with respect to a maximally entangled Bell state, with a success probability of 4×10^{-5}. We analyze the routes to improve these metrics, paving the way for long-distance networks of entangled quantum processors.

arXiv:2208.14907•Physical Review Letters•Feb 2, 2023•217 citations
We observe violation of a Bell inequality between the quantum states of two remote Yb+ ions separated by a distance of about 1 m with the detection loophole closed. The heralded entanglement of two ions is established via interference and joint detection of two emitted photons, whose polarization is entangled with each ion. The entanglement of remote qubits is also characterized by full quantum state tomography.
We report on the demonstration of ion–photon entanglement and Bell inequality violation in a system of trapped Ba138+ ions. Entanglement between the Zeeman sublevels of the ground state of a single Ba138+ ion and the polarization state of a single 493 nm photon emitted by the ion with a fidelity of 0.84±0.01 was achieved, along with a Bell signal of 2.3, exceeding the classical limit of 2 by more than eight standard deviations. This system is a promising candidate for a loophole-free Bell inequality violation test using long-range ion–ion entanglement as the wavelengths of the transitions of Ba138+ are in the visible region and thus suitable for long-range transmission over fiber optic cable.
Summary form only given. Here we present our experiment using heralded entanglement between two 87Rb-atoms separated by 400 m violating Bell's inequality [1]. First each atom is entangled with a photon, which is coupled into single-mode fiber. The interference of the two photons at a beam splitter enables one to project the state onto a Bell state, which leaves the atoms in an entangled state [2]. For space-like separation, the state measurements on the two atoms together with the random choice of the measurement basis, have to be performed in a time shorter than 1.33μs. The atomic state readout itself is based on a highly efficient state-selective ionization and subsequent detection of the ionization fragments by channel-electron-multipliers (CEM) [3]. Altogether the time for the state readout is below 1μs and the locality condition is fulfilled. Evaluation of 5000 events for each of two entangled atom-atom states shows a significant violation of Bell's inequality with S-parameters of 2.240 ± 0.047 and 2.204 ± 0.047.
Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of atoms). In order to constitute conclusive evidence, two conditions have to be satisfied. First, strict separation of the measurement events in the sense of special relativity is required ("locality loophole"). Second, almost all entangled pairs have to be detected (for particles in a maximally entangled state the required detector efficiency is 82.8%), which is hard to achieve experimentally ("detection loophole"). By using the recently demonstrated entanglement between single trapped atoms and single photons it becomes possible to entangle two atoms at a large distance via entanglement swapping. Combining the high detection efficiency achieved with atoms with the space-like separation of the atomic state detection events, both loopholes can be closed within the same experiment. In this paper we present estimations based on current experimental achievements which show that such an experiment is feasible in future.
Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of atoms). In order to constitute conclusive evidence, two conditions have to be satisfied. First, strict separation of the measurement events in the sense of special relativity is required ("locality loophole"). Second, almost all entangled pairs have to be detected (for particles in a maximally entangled state the required detector efficiency is 82.8%), which is hard to achieve experimentally ("detection loophole"). By using the recently demonstrated entanglement between single trapped atoms and single photons it becomes possible to entangle two atoms at a large distance via entanglement swapping. Combining the high detection efficiency achieved with atoms with the space-like separation of the atomic state detection events, both loopholes can be closed within the same experiment. In this paper we present estimations based on current experimental achievements which show that such an experiment is feasible in future.
We report on an elementary quantum network of two atomic ions separated by 230 m. The ions are trapped in different buildings and connected with 520(2) m of optical fiber. At each network node, the electronic state of an ion is entangled with the polarization state of a single cavity photon; subsequent to interference of the photons at a beam splitter, photon detection heralds entanglement between the two ions. Fidelities of up to (88.0+2.2-4.7)% are achieved with respect to a maximally entangled Bell state, with a success probability of 4×10^{-5}. We analyze the routes to improve these metrics, paving the way for long-distance networks of entangled quantum processors.