Quantum eraser

Let us quote the text from Ref. [15] "...a, Quantum eraser configuration in which electro-optic shutters separate microwave photons in two cavities from the thin-film semiconductor (detector wall) which absorbs microwave photons and acts as a photodetector, b, Density of particles on the screen depending upon whether a photocount is observed in the detector wall ( yes ) or not ( no ), demonstrating that correlations between event on the screen and the eraser photocount are necessary to retrieve the interference pattern."... 

The interference of microscopic particles leads to a diffraction pattern with deviations with respect to the mere sum of the individual probabilities. The two events are no longer independent. If we wish to state in advance where the next particle will appear, we are unable to do so. The best we can do is to say that the next particle is more likely to strike in one area than another. A limit to our knowledge, associated with the wave-matter duality, becomes apparent. In the double-slit experiment, we may know the momentum of each particle but we do not know an5 hing about the way the particles traverse the slits. Alternatively, we could think of an experiment that would enable us to decide through which slit the particle has passed, but then the experiment would be substantially different and the particles would arrive at the screen with different distributions. In particular, the two slits would become distinguishable and independent events would occur. No interference would be detected, that is, the wave nature of the particle would be absent. In such an experiment, in order to obtain information about the particle position just beyond the slits, we would change its momentum in an unknown way. Indeed, recent experiments have shown that interference can be made to disappear and reappear in a quantum eraser (ref. 6 and references therein). 

Pauli exclusion principle (p. 34) Pauli matrices (p. 29) quantum eraser (p. 46) qubit (p. 52)... 

Beeause the level with this L and S quantum numbers eontains (2L+1)(2S+1) states with Ml and Ms quantum numbers running from -L to L and from -S to S, respeetively, one must remove from the original box this number of produet states. To do so, one simply erases from the box one entry with eaeh sueh Ml and Ms value. Aetually, sinee the box need only show those entries with non-negative Ml and Ms values, only these entries need be explieitly deleted. In the example, this amounts to deleting nine produet states with Ml, Ms values of 1,1 1,0 1,-1 0,1 0,0 0,-1 -1,1 -1,0 -1,-1. 

If the entering particle was in a mixed state (relative to the r-spin measurement), then the act of measurement changes the state of the particle. No one understands how this happens, but it is an essential feature of the quantum mechanical model. For example, this phenomenon contributes to Heisenberg s uncertainty principle, whose most famous implication is that one cannot measure both the position and the momentum of a particle exactly. The point is that a position measurement changes the state of tlie particle in a way that erases information about the momentum, and vice versa. 

Thus, consider COT ) 1 and C(4>) 0 in the state vector [0(40 C(4> )]. This writing is made for convenience to emphasize that it is the excited state in the cavity which is of our interest. But you cannot erase the base states Hence, [0 1] refers the internal quantum state while the material system would be present but not localized. 

The answer in terms of internal quantum states is less evident. For, assume the photon left is now absorbed, and then the quantum state of the material support has not been necessarily restituted. This issue is examined now. We need supplementary base states Rb 61d5/2) 10a/) and Rb 61d5/2> 0a/>2. Now, if memory passage is erased and we get back the linear superpositions 3 + 7) and 3 — 7) that are equally possible, then we are back to the situation where either quantum state can be detected. This issue is now examined. 

For, the total quantum state as seen at the detecting screen if no distillation process applies is a mixture related to the alternatives "eraser photon yes or no."... 

F. Matsui, H. Taniguchi, Y. Yokoyama, K. Sugiyama, and Y. Kurita, Application of photochromic 5-dimethylaminoindolyl fulgide to photon-mode erasable optical memory media with non-destructive ability based on wavelength dependence of bleaching quantum yield, Chem. Lett., 1994, 1869-1872. 

At this stage, we are confident that a clear connection between Levy statistics and critical random events is established. We have also seen that non-Poisson renewal yields a class of GME with infinite memory, from within a perspective resting on trajectories with jumps that act as memory erasers. The non-Poisson and renewal character of these processes has two major effects. The former will be discussed in detail in Section XV, and the latter will be discussed in Section XVI. The first problem has to do with decoherence theory. As we shall see, decoherence theory denotes an approach avoiding the use of wave function collapses, with the supposedly equivalent adoption of quantum densities becoming diagonal in the pointer basis set. In Section XV we shall see that the decoherence theory is inadequate to derive non-Poisson renewal processes from quantum mechanics. In Section XVI we shall show that the non-Poisson renewal properties, revealed by the BQD experiments, rule out modulation as a possible approach to complexity. 

The cycloreversion quantum yield of 17b (0 = 0.00013) was much lower than that of 15b (O = 0.075). The very low cycloreversion quantum yield was found to increase steeply as much as 34-fold when the temperature was raised from 25 to 150°C. The large temperature dependence provides 17 with thermal-gated reactivity. The recorded memory in this system can be read many times with a weak laser, which does not raise the temperature of the medium. The memory can be erased with a high-intensity laser, which can raise the temperature of the medium to as high as 100-150 °C. 

Can molecules in a crystal or in a matrix also be used as storage units for information Can molecular systems be placed in a stable state which is measurably different from their initial state by light absorption, and can the information thus stored be read out or erased by a second light quantum Can such a functional unit attain a storage density which approaches the density of the molecules within a solid or on a surface ... 

There is an interesting connection between the energy needed to destroy entanglement, as indicated by this experiment, and the entropy production when quantum information is erased [30], Further experiments with femtosecond time resolution will probably help to clarify this connection and its possible influence on future quantum computer and communication systems. 

Moneypenny is absent from the universe altogether—a point that is further reinforced by a man appearing as M s assistant in Quantum of Solace. Moneypenny is termed Britain s last line of defense in On Her Majesty s Secret Service, and while the comment is flip, the moment she is erased fi om the Bond universe in Casino Royale and Quantum of Solace, 007 is breaking into M s home and stealing her passwords. She is a gatekeeper, and without her, Bond has one less restriction placed on him. 

The results in Table 1 and Fig. 2 demmistrate the progress which has been made since 1916 when Gilbert Lewis suggested the elecfrOTi-pair model. At the same time the essential kernel of his model is retained. The development of modem quantum chemical methods did not erase the intuitive proposal of Lewis, which is complemented and can now be quantitatively expressed by advanced models of quantum chemistry. 

---