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Two new experiments help blaze the trail toward quantum computing with teleportation

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Scientists are a little bit closer to faster computing and better encryption after two experiments discovered the first ways to reliably use quantum teleportation to transfer information.

Quantum teleportation involves quantum entanglement, in which two separate particles have an effect on one another. For example, if particle A is measured to be spinning up, it will cause particle B to assume a state where it is spinning down. If you know the state of particle A or B, you can infer the state of the other particle.

That allows the communication of information without actually physically transferring it through the air or a cable. The particles remain in place while influencing one another. Different particle states can represent the 1s or 0s of binary code, known as bits, which is used today in computing and telecommunication to encode information. String lots of them together and you can form words, commands and other data. Unlike traditional bits, quantum bits, or qubits, can carry a 1 and a 0 instead of just one or the other. This allows them to store more information more efficiently.

The first experiment (subscription required), which comes out of the University of Tokyo and Johannes Gutenberg University Mainz, transferred four qubits at a time with an accuracy of 79 to 82 percent. The qubits were sent more than 6,500 miles between Japan and Germany. Qubits have been transferred on-demand before, but at shorter distances and with a low success rate.

The researchers entangled big groups of photons, or light particles, instead of just two. This allowed more information to be sent at once.

The second experiment (subscription required) sent qubits over a much smaller distance: 6 millimeters. Researchers at the Swiss Federal Institute of Technology Zurich sent the information across a device that resembles a computer chip. It is the first time teleportation has been achieved within an electronic circuit. It is also the fastest teleportation system ever, as it is able to send 10,000 qubits a second.

“This is interesting, because such circuits are an important element for the construction of future quantum computers,” study lead Andreas Wallraff said in a release.

The Zurich researchers will now focus on increasing the distance over which the qubits are sent, potentially allowing communication between chips.

Scientists are interested in quantum teleportation because it could lead to faster, more efficient computing and communication. Photons travel at the speed of light and the connection in state between any entangled particles is nearly instant.

Teleportation is also more secure, as there is no signal being sent between two locations that could be intercepted. Quantum computers would also make better encryption possible because they can factor incredibly large numbers–an accomplishment out of reach for the average computer today.

9 Responses to “Two new experiments help blaze the trail toward quantum computing with teleportation”

  1. warptek

    I like your analogy. Perhaps the very reason we have not as yet received an alien signal. Wouldn’t it be the ultimate in irony if an alien civilization has been trying to contact us all along but we’re listening to radio signals instead of “subspace” signals?

  2. > if particle A is measured to be spinning up, it will cause particle B to assume a state where it is spinning down.

    I don’t think that statement is not correct. Here is my understanding of quantum cryptography, sure would appreciate any corrections:

    QM says we can not determine the outcome of a measurement with our models, but we can determine the probability of the outcome of a measurement. This is most pronounced at very small scales. For the EPR experiment this is true at both locations A and B of course. At both location A and B if we do not know in advance whether we will measure an arriving electron at spin up or spin down. In both locations we are equally surprised to find it in either state.

    However, if later we take our measurement results at point B and move them to point A, and compare them, then we will find that the corresponding electron measurements will always anti-correlate. If we measured up at point B, then the spin paired electron at point A will have been measured down. Unfortunately, we can not learn about this correlation at faster than the speed of light, because we have to bring our results together. Hence, we can send to point A a half a message, that of whether they should take the real information bit to be the opposite or the same as the measurement at point A. Without the information from point A, no one could make sense of this correlative data.

    And why do I say they are ‘spin paired’: well because of the Pauli exclusion principal we know that two electrons can occupy the same ‘orbit’ around a nucleus if one is spin up and the other spin down. So it seems that though the electrons were removed from the atom, and separated, they are still in some way connected by the exclusion principal. We say they are ‘entangled’. This appears to cause an exception to QM as we can know something about the outcome of the measurement – but this knowledge is about the correlation between the measurements and not the outcome of the measurements themselves. Unfortunately to make any use of this correlative information we have to bring the information learned in the measurements at point A and point B together. Hence we still have classical information to move, and this movement can not occur at faster than the speed of light.

    Hence, the reason that cryptographers find this useful is no just for secret communication via two channels, which can already be done, but rather for detecting eaves dropping. If someone does a measurement on the channel , then that measurement perturbs the electron’s state, perturbs the entanglement. Then when the perturbed electron arrives at point A the spin measurement produces random results (according to QM). So later when the correlative information arrives, it can not be made sense of as the original spin up or down information is missing. We can then know immediately that something is amiss.

    Still it seems we can have a man in the middle attack, as the man in the middle can measure the spin of an electron on a channel, then use a polarization filter to send down the channel an electron of the correct polarity. This man in the middle then needs the correlative information that is being moved classically in order to understand the message. Taking this further, if the man in the middle has the classically transported correlative information, he can manipulate can insert into the channel electrons of polarity to create any message he likes.

  3. David Dempster

    No signal is sent. Quantum entanglement is in essence “particle” A & “particle” B are the same particle for all practical purposes. The fact that they are in different places at the same time means that changing one changes the other instantaneously allowing for communication that is instant regardless of “distance”. Advanced civilizations would use such communication methods to communicate between “people” that were separated by light years of distance. Our search for exterrestrial intelligence, looking at the electromagnetic spectrum, may be like Indians seeing no smoke signals in the modern world and assuming there is no intelligent life communicating.

  4. jpwright

    The speedup in factoring large numbers provided by quantum computing would make many encryption algorithms obsolete. It would not make better encryption possible — unless someone develops new encryption algorithms.