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DON'T BEAM ME UP

With regard to "Quantum Teleporta-tion," by Anton Zeilinger, I decided to put the processing requirements related to teleporting a 150-pound person into perspective, bearing in mind that teleporting a few grams (about 1024 atoms) would require processing 1024 bits of information. Obviously you would not want to use Ethernet for any part of the data-acquisition system, because even the emerging 10-gigabytes-per-second flavor would leave you waiting at least 22 billion seconds to materialize. What about a direct connection to a multiprocessing supercomputer? Even if you could get your data at 10 teraflops, you'd still be a random collection of atoms for about 22 million years.

You definitely would not want to be teleported without first making a copy of your data; 22 million years is kind of a long time to expect a computer to run without crashing. I'd want my data on DVD, but this would require 22 billion DVDs. Alternatively, you could live dangerously and store yourself in RAM. At $75 per 64 megabytes, however, it would cost you $1,000,883,789,062,500,000,000.99. Fortunately, the 22 million years you have to raise it means you would only have to invest about $5,000 at 20 percent—roughly comparable to a flight on the Concorde.

DOUG MORGAN Irvine, Calif.

In the "Skeptics Corner" sidebar to the teleportation article, the author states that if each atom of iron in an automo-

bile were exchanged with an atom of iron from a lump of ore, the identity of the car would be retained, being the same in all properties. My understanding based on the article, however, is that teleportation would produce an identical person but not the same person. The new creature might believe he was the same as the original, but the original would have ceased to exist. I think that this manifestation of myself would decline the opportunity for teleportation, no matter the benefit to the successor manifestation.

JOHN C. TOSHACH via e-mail

Zeilinger replies:

i) hilosophers have discussed Toshach's question for more than 2,000 years. When is an object "identical to the original" and when is it "really the same"? Quantum physics teaches us that such distinctions only make sense if we can prove the difference by some observation or experiment. Therefore, because there is no way whatsoever to distinguish a perfectly teleported object from the original, it really is the same and not just identical.

SMART MICE

In "Building a Brainier Mouse," Joe Z.

Tsien notes that mouse intelligence is limited by NMDA receptor properties but that these properties can be modified to increase memory, apparently without undesirable side effects. Although he explains why the ability to memorize de-

THE MAIL

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NO SOONER HAD THE APRIL ISSUE shipped than reader reactions to "Quantum Teleportation," by Anton Zeilinger, began to materialize. Among the more imaginative responses were those proposing that only the neural structure of a person's brain need be transmitted to teleport a person-analogous perhaps to teleporting only the polarization state of a photon. Several people tried (fu-tilely) to find ways to transmit information faster than the speed of light, for example, by using multiple entangled particles and error-checking codes within the content of the transmitted message. And commenting on the accompanying cartoon, "The Quantum Adventures of Alice and Bob," an economist pointed out that the discovery of a vast supply of einsteinium crystals would depress the price of einsteinium, not raise it. He is correct— Bob should invest in www.einsteinium.com instead. Additional comments about this article and others in the April issue are featured above.

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SIDE EFFECTS for smartmice?

creases for older mice, Tsien does not address why natural selection has not further increased the time that the receptor is open (thus enhancing memory formation) for both juveniles and adults. Could such an enhancement lead to physiological side effects, or might the resulting higher intelligence lead to nonadaptive behavioral strategies? Such drawbacks would have fascinating implications for the development and administration of memory-boosting drugs.

ELLIOT NOMA

Metuchen, N.J.

Tsien replies:

Levels of learning and memory are not solely determined by the opening duration of the NMDA receptors. It is highly likely that other molecules and different levels in complexity of neural network and circuits in the brain play a significant role in determining these mental capacities. The influx of calcium through the NMDA receptor is critical, but too much of it may cause brain cells to die. Evolution may have already selected for the receptors to stay open longer but only up to the point at which the organism becomes sexually mature and reproduces.

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