Abstract. Two observers (Alice and Bob) independently prepare two sets of singlets. They test one particle of each singlet along an arbitrarily chosen direction and send the other particle to a third observer, Eve. At a later time, Eve performs joint tests on pairs of particles (one from Alice and one from Bob). According to Eve’s choice of test and to her results, Alice and Bob can sort into subsets the samples that they have already tested, and they can verify that each subset behaves as if it consisted of entangled pairs of distant particles, that have never communicated in the past, even indirectly via other particles. To appear in a special issue of Journal of Modern Optics. 1 1. Introduction and
Abstract. Two observers (Alice and Bob) independently prepare two sets of singlets. They test one particle of each singlet along an arbitrarily chosen direction and send the other particle to a third observer, Eve. At a later time, Eve performs joint tests on pairs of particles (one from Alice and one from Bob). According to Eve’s choice of test and to her results, Alice and Bob can sort into subsets the samples that they have already tested, and they can verify that each subset behaves as if it consisted of entangled pairs of distant particles, that have never communicated in the past, even indirectly via other particles. To appear in a special issue of Journal of Modern Optics. 1 1. Introduction and
Two observers (Alice and Bob) independently prepare two sets of singlets. They test one particle of each singlet along an arbitrarily chosen direction and send the other particle to a third observer, Eve. At a later time, Eve performs joint tests on pairs of particles (one from Alice and one from Bob). According to Eve's choice of test and to her results, Alice and Bob can sort into subsets the samples that they have already tested, and they can verify that each subset behaves as if it consisted of entangled pairs of distant particles that have never communicated in the past, even indirectly via other particles.
Two observers (Alice and Bob) independently prepare two sets of singlets. They test one particle of each singlet along an arbitrarily chosen direction and send the other particle to a third observer, Eve. At a later time, Eve performs joint tests on pairs of particles (one from Alice and one from Bob). According to Eve's choice of test and to her results, Alice and Bob can sort into subsets the samples that they have already tested, and they can verify that each subset behaves as if it consisted of entangled pairs of distant particles that have never communicated in the past, even indirectly via other particles.
Entanglement swapping is a fascinating generalization of quantum teleportation, where the entanglement between pairs is interchanged leading to entanglement between particles that never interacted. Extending the idea of Peres, we propose an experimental setup where the choice which quantum systems are finally entangled is made at a time after they have been registered and do not even exist anymore. Our proposed setup can be used in Third-Man Quantum Cryptography where a third party can control whether Alice and Bob are able to communicate secretly, but he does know their secret key.
This article develops an expanded critical-propositional analysis of Xiao-song Ma, Stefan Zotter, Johannes Kofler, Rupert Ursin, Thomas Jennewein, Časlav Brukner, and Anton Zeilinger’s 2012 experiment, “Experimental Delayed-Choice Entanglement Swapping,” published in Nature Physics 8: 479–484, DOI 10.1038/nphys2294, in systematic dialogue with the Theory of Objectivity (TO) formulated by Vidamor Cabannas and Denivaldo Silva. Ma et al. experimentally realized Asher Peres’s delayed-choice entanglement- swapping proposal by producing two entangled photon pairs and temporally delaying a randomly selected measurement on two of the photons until after the other two photons had already been detected. Victor’s later measurement could be configured either as a Bell-state measurement or as a separable-state measurement. Conditional sorting of the earlier records of Alice and Bob then yielded subensembles exhibiting either quantum entanglement or separable correlations. The experiment employed approximately 7 m optical paths for photons measured by Alice and Bob and approximately 104 m fiber delays for the photons sent to Victor. Victor’s measurement occurred about 485 ns after Alice’s and Bob’s detections, while his choice occurred between approximately 14 and 313 ns after those detections. The Bell-state configuration produced a reported fidelity of FBSM = 0.681 ± 0.034 and an entanglement-witness value of WBSM = −0.181 ± 0.034, whereas the separable-state configuration yielded a fidelity of FSSM = 0.421 ± 0.029 and a witness value of WSSM = 0.078 ± 0.029 (Ma et al. 2012). The article examines these results in relation to the Seven Absolute Truths of TO, with particular emphasis on the Fifth Absolute Truth, according to which an element requires relational observation or inclusion within the frequency of at least two other elements in order to possess logical existence. In TO, observation is not reducible to human consciousness; it is an objective relation among physical elements. The Ma experiment does not prove this universal modal proposition, but it offers an unusually relevant empirical domain in which physically meaningful classifications are dependent on multipartite relations rather than on isolated local records. The Fourth and Sixth Absolute Truths are likewise examined in relation to physical boundaries, interfaces, composition, and redistribution of entanglement. The Second Absolute Truth generates a productive tension with quantum indistinguishability, because TO attributes to every element its own exclusive field of individuation, whereas quantum optical interference presupposes operational indistinguishability among identical photons. Special attention is given to the TO concept of the transcendent element as knowledge or information generated in atomic relations and equivalent, within TO, to atomic radiation. Ma et al.’s experiment directly establishes an operational nexus among electromagnetic radiation, polarization information, physical correlations, measurement contexts, and recorded data, but it does not independently establish the stronger ontological identity between information and radiation proposed by TO. The article therefore distinguishes empirical consonance, operational compati- bility, ontological interpretation, and modal necessity. It argues that the scientifically strongest relation between Ma et al. and TO lies not in claiming confirmation of the entire theory but in constructing testable operational bridges, especially around relational observation, boundaries, physical information, non-simultaneity, and the dis- tinction between individual and relational properties. A TO-style appendix concludes the paper by formalizing possible operational bridges and research propositions for future empirical investigation. Keywords: Theory of Objectivity; delayed-choice entanglement swapping; quantum entanglement; relational observation; information; photon; Bell-state measurement; modal ontology; non-simultaneity; transcendent element; quantum foundations.
Entanglement swapping, the process to entangle two particles without coupling them in any way, is one of the most striking manifestations of the quantum-mechanical nonlocal characteristic. Besides fundamental interest, this process has applications in complex entanglement manipulation and quantum communication. Here we report a high-fidelity, unconditional entanglement swapping experiment in a superconducting circuit. The measured concurrence characterizing the qubit-qubit entanglement produced by swapping is above 0.75, confirming most of the entanglement of one qubit with its partner is deterministically transferred to another qubit that has never interacted with it. We further realize delayed-choice entanglement swapping, showing whether two qubits previously behaved as in an entangled state or as in a separable state is determined by a later choice of the type of measurement on their partners. This is the first demonstration of entanglement-separability duality in a deterministic way.
Entanglement appears under two different forms in quantum theory, namely, as a property of states of joint systems and as a property of measurement eigenstates in joint measurements. By combining these two aspects of entanglement, it is possible to generate nonlocality between particles that never interacted, using the protocol of entanglement swapping. We show that even in the more constraining bilocal scenario where distant sources of particles are assumed to be independent, i.e., to share no prior randomness, entanglement swapping can be simulated classically with bounded communication, using only 9 bits in total. Our result thus provides an upper bound on the nonlocality of the entanglement swapping process.