In an experiment featuring nonlinear optics, delayed choice and EPR-type correlations, the possibility of faster-than-light communication appears not totally implausible. Attempts are put forward and discussed to refute this claim.
Present understanding of non-possibility of Quantum communication rests on analysis of possibility of signalling within a Quantum system. Is it possible to achieve signalling by a setup where the system is changed from one to another where the act of change serves as the signal and the change in the measurement probabilities would be detected and deciphered at the receiver end? A proposal is made where a variant of Delayed Choice Quantum Eraser experiment setup of Kim et al is used to achieve the same. The setup is also designed such that the speed of communication can be faster than light. NonLocality and Quantum communication Nonlocality is a feature of Quantum Mechanics that has been firmly established through experiments [Aspect et al, 1981] and well accepted now. Entangled particles separated by a distance still are part of one entity and when that entity changes state by a measurement in one part of it the change happens instantaneously across the domain the entity pervades. Is it possible to use this instantaneous state change to transmit information across at high speeds, faster than light (FTL)? This issue has been dealt with from the time the Einstein raised the EPR paradox [Einstein et al,1935] and has been claimed to be impossible and shown to be so by Peres, [Peres and Tenko, 2004] through the no-communication theorem which shows that any amount of signalling by Alice through measurements done at one end of the quantum system would not be sufficient for Bob to detect and decipher at the other end of the system. However the discussions in literature (as above) always deal with information transfer within a stable quantum system by making measurements at one end and analysing the possibility of detecting it at the other end. Peres and Tenko analyse a Quantum System S of mixed-state where Alice and Bob make measurements at their ends of the system. The authors derive the probability that Bob’s outcome is ν as