![]() "However, it's well known that distant separable states cannot be entangled only by means of local operations and classical communication. ![]() "Entanglement is basic resource for many nonlocal quantum information tasks," Zhang notes. To achieve this counterfactual scheme by entangling two nonlocal qubits with each other without interaction, Zhang says that their main challenge was determining how to place the obstructing object in Salih's scheme in an unknown quantum superposition state of presence and absence. In short, existing quantum-information transfer schemes require a physical medium, and it was unclear if quantum information can be transferred without transmitting any physical particles – but this paper suggests that it can. In our scheme, entanglement sharing and classical communication are not needed." However, to date, schemes for the transfer of an unknown quantum state required physical particles to travel – for example, quantum teleportation needs prior entanglement sharing and classical communication, and both entanglement sharing and classical communication cannot be done without transmitting physical particles. "In quantum information science," Zhang continues, "the minimum information unit is quantum state-encoded qubit. In a chained quantum Zeno effect, a series of secondary splitter/detector loops ensure that there is never a significant probability of decoherence.) "This mind-boggling and highly counterintuitive communication protocol inspired us to think whether quantum information can be transferred counterfactually," Zhang adds, "so in fact, our present scheme can be considered as an incremental extension of Salih's work from classical bit to quantum bit." (In the quantum Zeno effect, time evolution caused by quantum decoherence in quantum systems is suppressed by, for example, continuous observation or measurement, interaction with the environment, or stochastic fields. By using the so-called chained quantum Zeno effect, the 2013 paper showed how information can in fact be transferred between two locations without any physical particles traveling between them. "There's a long-held assumption in the classical information field that information transfer requires physical particles to travel between sender and receiver – an assumption first challenged in 2013 by Hatim Salih and his colleagues 1," Zhang tells. Shou Zhang discussed the paper that he and his colleagues published in Scientific Reports. Moreover, the scientists state that their approach provides a new method for creating entanglement that allows two qubits to be entangled without interaction between them. The researchers accomplished this by entangling two nonlocal qubits with each other without interaction – meaning that the present scheme can transport an unknown qubit in a nondeterministic manner without prior entanglement sharing or classical communication between the participants. Now consider this: Recently, scientists in China at Harbin Institute of Technology, Yanbian University and Changchun University demonstrated what is known as a counterfactual approach in which quantum information can be transferred between two distant participants without sending any physical particles between them. ()-While Einstein considered quantum entanglement as "spooky action at a distance," and those who fully accept entanglement acknowledge it to be counterintuitive, current entanglement-based quantum communication schemes for transferring an unknown quantum state from one place to another require classical transportation of particles between sender and receiver. Copyright © 2015, Rights Managed by Nature Publishing Group. Counterfactual quantum-information transfer without transmitting any physical particles. Credit: Guo, Q., Cheng, L.-Y., Chen, L., Wang, H.-F. ![]() The photon will be absorbed by the ensemble for the control atomic state | g>, and will pass through the ensemble for the control atomic state | r >. ![]() The single atom controls the transmission properties of the ensemble by Rydberg dipole interaction. A control atom and a mesoscopic Rydberg atomic ensemble are stored in two separate trapping potentials, and the ensemble forms a superatom with the collective ground state |G> and the Rydberg state |R>. Figure 1 | Quantum control device for the passing or blocking of the incident single photon with the frequency ω. ![]()
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