During the last two decades have been successfully developed the quantum cryptography techniques that rely either on manipulation of the polarized single photons or the entangled photon pairs. At that has been found confirmation the fact the quantum correlations between the entangled photons are nearly or totally instantaneous but those correlations cannot be used for the direct superluminal information transfer as the state of the photon in the pair is unknown before the first measurement. Technology of entangled photons has made possible the modified double slit experiments where the appearance of the interference picture in detecting of the “signal” photons may be controlled by the manipulation of the spatially separated “idle” photons. In the present paper we discuss the possible superfast communication channel between the entanglement-linked distant parties using the remote manipulation of the interference picture formed statistically by the number of signal photons.
During the last two decades have been successfully developed the quantum cryptography techniques that rely either on manipulation of the polarized single photons or the entangled photon pairs. At that has been found confirmation the fact the quantum correlations between the entangled photons are nearly or totally instantaneous but those correlations cannot be used for the direct superluminal information transfer as the state of the photon in the pair is unknown before the first measurement. Technology of entangled photons has made possible the modified double slit experiments where the appearance of the interference picture in detecting of the “signal” photons may be controlled by the manipulation of the spatially separated “idle” photons. In the present paper we discuss the possible superfast communication channel between the entanglement-linked distant parties using the remote manipulation of the interference picture formed statistically by the number of signal photons.
A means and protocol is presented to send information on the Bell Channel to achieve the effect of superluminal signalling. The method is to use detection of a photon entangled state as one binary digit and either of the collapsed states as the complement digit - this is the protocol. The means to affect this detection is by use of an interferometer set-up able to resolve two interfering pathways corresponding to the two polarization states of the photon. To achieve interference of the horizontal and vertical components Faraday rotators are used to bring both components into diagonal polarization, this operation is unitary. Modulation is caused by the remote signaller collapsing one aspect of the photon wavefunction; a physically secure channel sending information superluminally results. A preliminary discussion into the clash and the hopeful resolution with Relativity theory is presented - it is noteworthy that at the instant of transmission between the two stations that there is no transfer of mass-energy to instigate communication but the transmission of a quantum state - pure information only.
In this paper we present a theoretical analysis of the faster than light communication possibility based on entangled photons. We analyze designs that may be capable to solve the problem of direct information transfer between members of an entangled photon pairs. We consider that experimental verifications can confirm or even refute this. Our hypothesis was that most proofs of the nocommunication theorem are based on a certain set of conditions, and it is possible to provide a broader set of conditions that allow the establishment of entangled states as quantum information channels, without using a classical channel. One basic unit of the proposed design transforms the polarization state of one member of an entangled photon pair into a spatial superposition state. Thus, after the polarization measurement performed on one member, which eliminates the entanglement, the quantum information is maintained in the spatial superposition state of the other member. This can be recovered by a particular measurement based on spatial interference. We have shown that solutions with so-called symmetric functions lead to average results that corresponds to the nocommunication theorem. However, using asymmetric functions the averaged measurement results calculated in a prescribed time window can distinguish the types of measurements performed on the other member of the pair. This can establish a communication code that enables faster-than-light information sharing under specific conditions. There may be also further theoretical consequences: a significant extension of the quantum mechanical nonlocality principle.
Abstract In Quantum Mechanics, two particles are entangled if their physical states depend on one another's so that if we find one of them in state A, for example, we will be sure that the other is in state B. However, until the state of a quantum particle is measured, it will be in a superposition of states, being in neither one nor the other until then, so when an entangled particle is measured, its pair also assumes a state instantly and regardless of how far away it is from the other particle at that time. As promising as it could be to use this fact for instantaneous communication, Quantum Mechanics seems to claim this is impossible, as no method ever invented to do this has worked until today. What we demonstrate here theoretically is that with a protocol and simple optical devices, two people who share polarized entangled pairs of photons can send information to each other faster than light. If this model of communication proves to be experimentally functional, we will have a contradiction to Einstein's theories of relativity, and otherwise, we will have Quantum Mechanics predicting something that does not happen in real life. This result, therefore, shows there is something fundamental about the universe we do not know yet. One of these theories must be mistaken and both deal with fundamental aspects of reality, such as the dynamics of space and time, and the particles that almost all matter around us are made of. Besides, this result is of great relevance also because it has immediate applications in several areas if the model works experimentally, as in space exploration and security, since it will allow the creation of non-interceptable instantaneous communication technologies.
In this paper, we introduce a secure optical communication protocol that harnesses quantum correlation within entangled photon pairs. A message written by acting on one of the photons can be read by measuring exclusively the other photon of the pair. In this scheme, a bright, meaningless optical beam hides the message, rendering it inaccessible to potential eavesdroppers. Unlike traditional methods, our approach only affects unauthorized users, fundamentally limiting their access to the communication channel. We demonstrate the effectiveness of our protocol by achieving secure communication through both amplitude and phase modulation, relying on single-photon measurements, as opposed to most approaches which rely on coincidence measurements. We successfully demonstrate the resilience of the data transfer to noise up to 105 times greater than the signal, and we employ this technique for the secure transfer of an image.
We propose a protocol for transferring photons of unknown states to a distant location using path-polarization hybrid entanglement. Our protocol uses a polarizing beam splitter (PBS), a beam splitter (BS), a CNOT-operation, four unitary operations and polarizing detectors. In our protocol, the hybrid entangled states are generated by the PBS, and it is transmitted through the quantum channel containing the BS and CNOT-gate. The measurement results of the polarizing detectors and classical communications determine which unitary operation will be used in the last step for recovering initial states. The security of the channel in transmitting unknown photons between two parties is confirmed by the results of the measurement of each target photon in the control mode.
At the heart of quantum physics lies the principle of superposition, and at the heart of information theory lies the bit. Perhaps the most useful property of quantum systems is that they can be loaded with information bits, so-called qubits, that are indefinitely both 0 and 1 until a measurement is made. Another consequence is that several qubits can become entangled, which is manifested by the non-classical correlations between such quantum systems when measured in all possible bases. Within the rapidly progressing fields of quantum information and quantum communication these quantum effects are utilized to perform tasks such as quantum computing and quantum cryptography. In this thesis we present experimental and theoretical work using single photon sources to prepare ``flying'' photonic qubits. We describe work using mainly quasi-phase-matched nonlinear crystals to generate beams of entangled photon pairs, that are either encoded in polarization at near-visible wavelengths, or in time at optical fiber telecommunication wavelengths (1550 nm). The optical fiber is the medium used for transporting the qubits over a long distance, and it is therefore essential to couple the photons well into the fibers. By focusing the beams optimally, we have investigated how this problem can meet the requirement of creating photons of a narrow frequency bandwidth and a high photon flux. Furthermore, we have generated truly single photons that are heralded by an electrical signal. As a result of modifying the statistics of such sources we have been able to show the effect of photon antibunching. In two separate works, we have implemented a quantum key distribution system based on faint laser pulses at the telecom wavelength of 1550 nm, as well as protocols based on entanglement for performing authentication of key distribution in quantum cryptography.