Keyword research, which will prove the principle possibility of quantum teleportation of photons.
This is necessary for fundamental physical reasons of principle possibility of distant broadcast genetic and metabolic information using polarized (spiniruûŝih) photons. Proof, applicable both to translate in vitro (with a laser), and in vivo, i.e.. in the biological system between cells.
Experimentally demonstrated quantum teleportation – transfer and restore on any arbitrary distance state quantum system. In the process of teleportation primary photon is polarized, and this polarization is passed to the distant State of. The pair tangled photons is the object of measurement, the second photon of the confused pair can be arbitrarily far from the initial. Quantum teleportation is a key element in quantum computing.
The dream of teleporting – It is the dream of the ability to travel simply by appearing at a distance. A teleportation can be completely characterized by its properties of classical physics by measurements. In order for the, to some distance to make a copy of this object, it is not necessary to pass to parts or pieces of. All, What is necessary for this transfer – It is filmed with a full information about it, that can be used to recreate the object. But how accurate is this information to generate an exact copy of the original? If these parts and pieces will be presented by electrons, atoms and molecules? What will happen to their individual quantum properties, which, According to Heisenberg’s uncertainty principle, cannot be measured with any precision?
Bennett and others.  proven, It is possible to transfer the quantum state of one particle to another, i.e.. the process of quantum teleportation, that does not transfer any information about this condition in the process of transferring. This difficulty can be overcome, If you use the principle of tangle-free (entanglement), the special properties of quantum mechanics . It shows the correlation between quantum systems significantly more strictly, than it can do all the classic correlation. Possibility of transmission of quantum information – one of the basic structures of the wave quantum communications and quantum computing . Although there was rapid progress in quantum information processing, difficulties in managing the quantum systems do not allow you to make adequate progress in the experimental implementation of new proposals. Not promising rapid strides in quantum cryptography (the primary considerations for the transfer of sensitive data), previously we only successfully proved the possibility of quantum dense coding , as quantum mechanical amplification data compression. The main reason for this slow progress in experimental, that although there are methods of generating pairs of tangled photons , tangled State atoms are only beginning to be studied  and they are no more available, the muddled State of two ticks.
Here we publish the first experimental verification of quantum teleportation. By creating pairs of photons through the tangled process of parametric down-conversion, as well as through the dvuhfotonnoj Interferometry for analysis of tangle-free, We can supply quantum properties (in our case, the polarization State) from one photon to another. Methods, developed in this experiment, will be of great importance for research in quantum communication, and future experiments on the fundamentals of quantum mechanics.
For a clearer understanding of the problem of transfer of quantum information, Let’s say, that Alice has some part of the quantum state |Ψ|, and she wants to send to Bob, located on certain distance, the same part in the same State. I see, that there is a possibility to send Bob a particle directly. But suppose, What channel of communications between Alice and Bob is not very good for keeping the necessary quantum coherence, or let’s say, that the transfer would take too long and this will cause the, that |Ψ| become more complex or large object. So, What should be the strategic behavior of Alice’s and Bob’s?
As noted above, There is no such measurements, that would be Alice by |Ψ|, that would have been sufficient to reconstitute them to Bob, because the State of a quantum system can never be fully determined by measurements. Quantum systems so elusive, as they can be in a superposition of multiple States at one time. Measurement of a quantum system is accurate only in one of these States, and this will be one of the key provisions of the proposed model. We can demonstrate this important quantum property, taking a single photon, which may have horizontal or vertical polarization, tagged conditions |↔| and | |. It can even have a total superposition of the two polarization States. (1)
|Ψ|= α|↔|+ b| |
where α and β are two complex numbers, satisfying |α|² |β|² = 1
Given this sample in the more general case, We can replace State |↔| and | | in the equation (1) on |0| and |1| , who represent States of any quantum system in two States. Superposition |0| and |1| called qubits (qubits), they have important new features, imposed by quantum physics in information science .
If the photon is able to |Ψ> passes through a polarizing beam disintegrant (the reflection device horizontally or vertically polarized photons), It is found in the reflected (the passed) Ray with probability |α|²(|β|²). The differentiation of the general condition of the |Ψ| It is possible to predict how the path to the |↔| , and on the way | | Depending on the measure. We believe, that the laws of quantum mechanics, in particular, the postulate (projection) forecast of this kind, Alice’s makes it impossible for accurate measurement |↔|, i.e.. Unable to obtain all the information, that is needed for the reconstruction of the State.
The concept of quantum teleportation
Although tenet prediction in quantum mechanics seems to be sufficient for Alice’s attempts to ensure the right transition from Bob in the State |↔| (as the equivalent of taking teleportacionnoj information from Alice to Bob (P.G.)), However,, This became possible after the work of Bennett and others. , who were able to accurately predict the teleportation State |↔| from Alice to Bob. During the teleportation Alice will destroy (own? P.G.) quantum state at the time of admission Bob (new P.g.) quantum state (sent it? P.G.), and at the same time, neither Bob, no Alice did not have accurate information about the status of |↔|. A key role in the scheme of teleportation are further tangled pair of particles, the first are Alice and Bob.
Suppose, particle 1, that Alice wishes to teleport, is in a State of
|Ψ|1 = a|↔|1 + b| |1 (Figure 1a), and entangled pair of particles 2 and 3, manipulated, Alice and Bob, possess the status of (2)
|Ψ-|2 3=1/√2 |↔|2 | |3 – | |2 |↔|3
Such a mixed pair in a single quantum system, equivalent to a superposition of States
|↔|2 | |3 and | |2 |↔|3. A mixed state does not contain any information about individual particles; It only indicates, the particles will be in opposite conditions. An important property of the mixed pairs is, as soon as the State of one particle is measured, such polarization is able |↔|, the other particle would have no middle ground (orthogonally P.g.) | |, and vice versa. How measuring one particle instantly affects the State of the other particle, which can reside indefinitely far? Einstein among the many achievements of the physicists did not recognize this action of ghosts at a distance „. But the disputed status of the sputannogo property is demonstrated by numerous experiments [see. 9 reviews,10].
Teleportation scheme works as follows:. Alice has a particle 1 in the initial state |Ψ|1 and particle 2. Particle 2 confused with the particle 3, that goes to Bob. A special moment – a special dimension to particles 1 and 2, that translates into sputannoe State: (3)
|Ψ-|1 2=1/√2 |↔|2 | |3 – | |2 |↔|3
This is just one of the possible maximum tangled State, in which two particles can be translated. Prediction of the indeterminate state of two particles based on their (the likely? P.G.) four States called Bellovskoe status measurement (Bell state measurement). State Of The, given in the equation (3), finds himself of the other three most confusing State of the, that its change is based on the changes of intermediate particle 1 and particle 2. This unique property antisimmetričeskoe |Ψ-|February 1 will play an important role in the experimental identification, that is, the dimension of this condition.
Quantum physics predicts , that if the particles 1 and 2 are predicted in the state of |Ψ-|1 2, the particle 3 immediately revert to the initial state of a particle 1. The reason for this is the following. As we watch the particles 1 and 2 in the state |Ψ-|1 2, then we know, that at a certain state of particle 1, particle 2 will be in the opposite state, ie in a state of orthogonal particle 1. But we immediately transferred particles 2, and 3 in state |Ψ-|2 3, and that means, 2 that the particle also orthogonal particle 3. This is only possible, If the particle 3 is in the same state, and that the particle 1 was initially. The final state of the particle 3 so: (4)
|Ψ|3 = a|↔|3 + b| |3
Note, that during Bell’s measurement of particle 1 is losing self-identity, as starting entangled with particle 2. Therefore, in the process of teleportation State |Ψ|1 Alice is lost.
This result (equation (4)) deserves some comments. The transfer quantum information from one particle to particle 3 may occur over any distance, and that is by teleportation. Experiments show , that quantum entanglement remains at distances greater than 10 km. Also,, that in the scheme of teleportation is not necessary, Alice to know where is Bob. Moreover, the initial state of a particle 1 may be completely unknown, not only to Alice, but to anyone. The full quantum-mechanical uncertainty can occur even if, When the Bellovskoe status measurement. This is then, as has been mentioned by Bennett et al , when the particle itself is one member of a pair of entangled and therefore does not have well-defined properties. This eventually leads to procrastination in confusion [12,13].
It is also important to stress, that Bellovskoe status measurement do not reveal any information about the properties of any particles. It Is Clear, why quantum mechanics works using coherent ensembles of superpozicionnyh pairs of particles, While any measurement on single superpozicionnyh particles would be doomed to failure. The, that absolutely no information is acquired by any particle – also the reason why quantum teleportation avoids verdict analogue of a theorem . After the successful teleportation of particle 1 is already no longer available in its natural state, and therefore the particle 3 is not an analogue, She – the result of actual teleportation (and transport properties from 1 to 3 (P.G.)).
Full Bellovskoe status measurement can provide not only the result of, that two particles 1 and 2 are in the state of antisymmetric, but a 25% chance we can find them in any of the other three entangled states. When this happens, particles 3 included in one of three different states. Bob then it is translated to the original state of the particle 1 in accordance with the selected transform, independent of the state of a particle 1. This is after taking a classical communication channel information, that Alice was based on analysis of Bellovskogo. Finally, Special note, even if we wanted to identify only one of the four Bellovskih States, as discussed above, Teleport will be successful, Although only a quarter of the cases.
Teleportation is closely linked with the generation and measurement of photon matted; They are the most important tasks for any experimental confirmation. Until now there were only few experimental facilities, that can be confusing State education, and there is no experimentally verified data, to determine all the four Bellovskih States for any kind of quantum systems. However,, entangled pair of photons can easily get, and they may be anticipated in at least two of the four Bellovskih States.
We got entangled photons 2 and 3 by parametric down-conversion. In this method, the, in the nonlinear Crystal, entering through the pumping photon may spontaneously decay into two photons, which, in the case of a type 2 parametric down-conversion are able, This in the equation (2) (Fig. 2) .
In order to achieve the prediction of photons 1 and 2 in Bell’s condition, We have to make them indistinguishable. To achieve this indistinguishability, These two photons we translate in the superposition of a rasŝepitele beam (Figure 1b). If they fall down each side, How is it, that each of them still appears on the sides of the? I see, that this could happen, If they are recognised, or turn. In quantum physics, we must have a superposition of voltages for these two probabilities. Single pulses, the amplitude of the reflected, received by adding negative signals. However,, It seems, that these two processes mutually exclusive. However,, It is only symmetric input status. To antisymmetric State of these two possibilities are other related negative signal, and therefore, they interfere with [15,16]. This satisfies the prediction of photons 1 and 2 the antisymmetric state |Ψ|February 1 in order to place the detectors in each of the splitter outputs, and for simultaneous registration (matches) [17-19].
To be sure, that photons 1 and 2 are indistinguishable at the time of their arrival, their generirut, using pulse beam pumping, and direct through the filters with narrow bandwidth, giving time coherence much more, than the length of the pulse pumping . The experiment had a pumping pulse duration of 200 fs at the repetition frequency 76 MHz. Analysis of the down-converted photons with a wavelength of 788 nm with a slit width of 4 nm showed, their coherence time was 520 fs. This should be understood as, 1 that since the photon is also produced as part of a tangled pairs, its partner can serve as an indicator of the occurrence of the photon 1.
How can the only experiment to prove, an unknown quantum state can teleport? Firstly it should fully demonstrate the, that teleportation is the only known States, where any other conditions disappear. The main thing in their States two polarization components, and, in principle,, We can recognize the horizontal or vertical polarization of radiation source. But it’s still not showing, the teleport works for any general superposition, Since the two lines are preferred in our experiments. Therefore, in the first experiment, we choose as a basis teleportation two states of linear polarization of -450 and +450, that already have a superposition of horizontal and vertical polarization. Secondly, the experiment must prove, that teleportation is working on these two fundamental conditions superpoziciâh. Therefore, we also demonstrate teleportation for circular polarization.
In the first experiment 1 was polarized photon 450. Teleportation fire as soon as photons 1 and 2 were determined in the state |Ψ|1 2, which is observed in 25% of all possible cases. State Of The
|Ψ|February 1 determined recording overlap between the two detectors f1 and f2 , placed behind disintegrant beam (Figure 1b).
If we have a match f1f2 (between the detectors f1 and f2), 3 also while the photon is polarized at 450 . 3, the photon polarization is analyzed by passing it through a polarization beam splitter, separating -450 and +450 polarization. To demonstrate teleportation (When the beam of the polarizing disintegrant) beeps (registration detection) Once the detector d2 450 and once detectors f1 and f2. Detector d1 at -450 at the output of the polarization beam splitter does not detect the photon. So the record three-times match d2f1f2 (+450 analysis) together with the lack of three-times match d1f1f2 (-450 analysis) is dokazatel′tvom the, 1 that the photon is polarized photon teleported to 3. To perform a temporary overlay, we change in small steps while the photon arrival 2, adjusting the delay between the first and the second down conversion by obratnootražaûŝego mirror (Figure 1b). In this way, we scan the temporary overlay district rasŝepitele beam in order, to observe the teleportation.
Outside the region teleportation each of photons 1 and 2 will go to f1 or f2 independently. The probability of overlap between f1 and f2 is why 50%, that is twice the area of teleportation. Photon 3 has a certain polarization, as an integral part of the confused pair. Therefore, d1 and d2 both have a 50% chance of getting photon 3. This explains the 25% probability for both cases -450 Analysis (match d1f1f2) and +450 Analysis (match d2f1f2) outside the field of teleportation. Fig. 3. Adds predictions of how the delay function. The success of teleportation +450 polarization state is also proved by a decrease to zero at -450 analysis (Fig. 3a) and the same condition for 450 analysis (Fig. 3b).
Theoretical prediction fig. 3 can be accurately interpreted, If we take into account, that lag time reduces by half the matches for two detectors in Bellovskih State analyzers f1 and f2, in comparison with the area outside of the teleportation. Therefore,, If the photon polarization 3 does not correlate with other polarizations, It also indicates, that 3-multiple matches reduced by half. The correct photon States the fact Jesus falling curve to zero in Fig. 3a and flat curve in Figure. 3b.
Note, it is equally probable as the production of photons 1, 2 and 3, and the emission of a single source of two down-converted photon pairs. Although there is no photon, coming out of the first source (foton1 is missing), contribution to three times the current rate matches will still be significant. These matches are irrelevant for teleportation and can be interpreted as an indication of blocking the passage of the photon 1. The probability of a random 2-and 3-multiple matches for these processes can be calculated from the experimental results. The experimentally determined value for the 3-multiple coincidences of 68% 1%. The experimental graph Figure 4 we empirically deducted certain random coincidences.
Experimental results for photons, polarized at +450, shown in the left column, fig. 4; Fig. 4a and b should be compared with the theoretical predictions in Figure 3. A strong decrease in signal analysis and -450 constant signal level at +450 analysis shows, 3 that the photon is polarized along the direction (direction along the) photon 1, and this confirms the teleportation.
Tab. 1. The reality of teleportation in 3 ‘s multiple matches
Polarization ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ ⁕ Reality (Visibility)
Results for photon 1, polarized at -450, show, that teleportation is working on a full-scale basis of polarization States (right column fig. 4). We conducted additional research, to exclude any classical explanation of our experimental results and confirm their. In this section we teleported linearly polarized photons 00 and 900, as well as teleported photons with circular polarization. These results are summarized in Table 1., where we demonstrate the reality of the accuracy of 3-x x matches, observed in the orthogonal polarization over analysis.
As stated above, the accuracy obtained after subtracting the random 3-multiple matches. This can be experimentally possible to create the conditions for a 3-fold in the detection of photon coincidences 4, which actually enters one photon in the state of one particle. We measured a 4-fold coincidence in the case of 450 and 900 polarization states, as with the 2-x not orthogonal States.
The following steps
In our experiments we used a pair of polarized photon matted, which are obtained by means of an impulse down-conversion and dvuhfotonnoj Interferometry for the State of polarization of photons from one State to another. But teleportation does not mean, that can only work systems. In addition to pairs of photons or atoms tangled tangled as working you can imagine tangled photons with atoms or photons, ions, etc.. You can then allow the transport conditions such, like for example, fast quantum Decoherence and short lived particles, on some of the more stable system. This opens the prospect of quantum memory, where the information, penosimaâ photons, stored in ion traps, carefully shielded from the environment.
In the future, using the cleaning sputyvaniem  – method of improving quality of entanglements with junk Decoherence is proposed during the storing or transmitting particles through noisy channels – it becomes possible to teleport quantum state of a particle in a certain place, even if quantum channels very poor quality so that particles will likely lose its fragile quantum state. The ability to protect quantum States in adverse conditions is of great importance in the field of quantum computing. Teleportation scheme, can also be used to provide links between quantum computers.
Quantum teleportation – This is not only an important component in quantum information tasks; It also allows you to put new types of experiments and research in fundamental quantum mechanics. Like any quantum state can be teleportirovano, and, Vice versa, It may be undefined for a particle – Member of the confused pair. Similarly to the entanglements between particles. This allows us to provide not only a chain of transmission of quantum States on distance, where quantum Decoherence has already resolved the status of complementarity (pairs of particles, P.G.), but it also allows us to test particle Bella theorem, that does not impact in any way on the past.
Is this the next step in future studies of quantum mechanics. Most, but not least. Disputes over the local accuracy of understanding nature can stop, If future experiments are used to generate a tangle-free for more than two spatially separated particles.
Fig. 1. Scheme, showing the operating principles of quantum teleportation ((a) and experimental plant ((b). (a, Alice has a quantum system, particle 1, in the initial state, She wants to send to Bob. Alice and Bob also possess additional pair of entangled photons 2 and 3, emitted by the source of the Einstein-Podolsky-Rosen (EPR). Alice then conducts combined (joint) Analysis Of Bellovskogo Condition (Bell state measurement, BSM) the initial photon and an additional, intended for transfer sputannoe status. It then sends the result of the measurement of both classical information to Bob, It is a unitary translation (U) on another extra photon, wherein the receiving state of a particle 1. (b, Pulsed UV light, passing through a non-linear Crystal, It creates an additional pair of photons 2 and 3. In a reverse reflection of the, After the second pass through the Crystal, the other pair of photons, one of which will be set in the initial state of the photon 1 teleportation, the other serves as a trigger, pointing, that the photon must be put by others. Alice then tracks the match after disintegrant beam (BS), where the initial photon and an additional superpozicioniruûtsâ (superposed). Bob, After taking the classical information, that Alice got just counts in the detectors f1 and f2, identifying Bellovskoe status |Ψ-|1 2, knows, that his photon 3 is identical to the initial state of photon 1. Bob can check this, using the polarization analysis with polarizing beam Builder (PBS) and detectors d1 and d2. Detector p gives information, 1 that the photon in another way (under way).
Fig. 2. Photons, created by type II down-conversion (see. the text of the) in Figure 1. 2. Picture perpendicular dissemination. Photons are produced by steam. Photon (the upper circle) polarized horizontally, While the other photon (lower range) polarized vertically. In points of intersections of the circles of the polarization of photons is vague and all, What is known about them – This is something, that they are different and the, What is their condition is a result of them tangle-free.
Fig. 3. Theoretical prediction of probability 3-times the match between the two detectors Bellovskogo status (f1,f2) and one of them registers State teleportation. Elevation teleportation polarization state of a photon in a 450 drop to zero at zero delay to a 3-fold coincidence detector, analyzing -450 (d1f1f2) ((a) and the constant value for the detector, analyzing +450 (d2f1f2) ((b). Hatched area shows the bounds of teleportation.
Fig. 4. The experimental results. Measured values of the 3-times the match d1f1f2 (-450) and d2f1f2 (+450) in the case of the polarization state at teleportation +450 ((a) and (b)) or at -450 ((c) and (d)). The values are plotted as a function of the coincidence delay arrival of photons 1 and 2 on the beam splitter Alice (see. Figure 1b). 3x coincidence of the values applied after subtraction of the random 3-fold contribution (see. the text of the). These data, in comparison to figure 3, together with similar results for other polarizations (Table 1) support for arbitrary State teleportation.
Fig. 5. Values 4-multiple matches (without the background subtraction). Conditions for the 3-fold coincidence with similar Fig.4 photon registration 4 (see. Figure 1b) the subtract join’s 3 ‘s multiple background začenij. a and b values show 4-fold in the case of coincidence of the polarization state teleportation +450. You Can See, that matches with such polarization teleported photons obtained without any background subtraction and comprise 70% 3%. These results on teleportation two orthogonal States prove, We got the single photon quantum state teleportation.
Experimental quantum teleportation.
DIK Bouwmeester, Jian-Wei pan, Klaus Mattle, Edathala, Harald Weinfurter & Anton Zeilinger.
Nature, v. 390, N11, pp. 575-579, December 1997.
(ПЕРЕВОД П. П. ГАРЯЕВА, ИПУ РАН)