Researchers Control the Flip of Electron Spin

karvind writes "According to PhysOrg, physicists in Europe, California and at Ohio University now have found a way to manipulate the spin of an electron with a jolt of voltage from a battery. In this experiment voltage was applied to Indium Arsenide based quantum dot which flipped the spin of electron inside it and emitted a photon. The scientists were able to manipulate how long it would take for the electron to flip its spin and emit a photon - from one to 20 nanoseconds. This may have possible applications in optoelectronics and quantum cryptography. Results were published in the latest issue of Physics Review Letters"

Comments

Election?

[Anonymous Coward]

Was I the only one who thought this read "Researchers Control the Flip of Election Spin"?

As Usual

[superpulpsicle]

All universities new findings take 30 years before they are applied to the corporate world.

1.) show the slashdot how electron flips
2.) slashdot crowd say cool
3.) show more engineers
4.) show sponsors, marketers, businessmen
5.) repeat step 4 for 29 years
6.) profit!

20/20 Hindsight

[yotto]

*...voltage was applied to Indium Arsenide based quantum dot which flipped the spin of electron inside it and emitted a photon. The scientists were able to manipulate how long it would take for the electron to flip its spin and emit a photon - from one to 20 nanoseconds.*

When you put it that way, I don't know why it wasn't this simple the whole time!

Not exactly ...

[maxwell demon]

The title of the linked-to article in Physical Review Letters is:
"Voltage Control of the Spin Dynamics of an Exciton in a Semiconductor Quantum Dot"
(Emphasis by be)
Now an exciton is something quite different from an electron.

Mmmm... Dark exitons

[gerbalblaste]

"A dark exciton with total angular momentum L=2 ecomes a bright exciton with L=1."
Finally a practical application for decay dynamics following nongeminate excitation

Re:Quantum computing?

[heelios]

Not exactly I am afraid. There are still huge issues to quantum computing. Namely isolation and data retrieval.

A quantum computer (or at least it's processor) needs to be totally shielded to the outside world while it operates as any interraction or mesurement from the outside world will break the theory. Also, at this moment, you cannot retrieve the processed data without interfering, right? So as soon as you get the data from one of the virtual processors working in 'other worlds', the thing breaks and you can't get anything anymore from it. So it's in fact pretty useless I'm afraid.

I don't think we're going to see a quantum computer in the years to come, and much less under our desks. Even if they were invented I believe our governments will keep them away from us as they could be quite mean to encryption.

Entanglement doesn't work that way

[Asparfame]

By "Pair off two electrons", I presume you mean put them in an entangled state where the spins of the two electrons are correlated? (For example, in the state |up, down> + |down, up>).

In that case, your system won't work. Putting one of the electroncs in this spin-flipping device would destroy the fragile entanglement. In other words, flipping the spin of one would do nothing to the other.

This is how it always is with entanglement -- entangled particles only remain entangled as long as you leave their entangled properties alone. Once you measure or modify the properties of one, the entanglement is ruined.

Re:Entanglement doesn't work that way

[Asparfame]

Proviso: When I said that modifying the properties of one member of the pair ruins the entanglement, that was not completely correct. If you managed to come up with a scheme to flip the spin of one without measuring the spin, then entanglement would be maintained. However, this would still not flip the spin of the other electron -- the entanglement would not have a different character.

Example: You start with the electrons having opposite (but indeterminate) spins, in the entangled state

|down, up> + |up, down>

(normalization constant ignored)

Now you flip the spin of the first electron. This puts you in the entangled state

|up, up> + |down, down>

Entanglement is preserved, however, you have not "flipped the spin" of the second electron. You have changed the sense of the correleation though. But you still haven't transmitted any information. The spin of each individual electron was indeterminate before you meddled, and was after you meddled.

When I said the measuring the relevant property of one of the pairs ruins the entanglement, well, that was still correct. And try as you might, there is no way to transmit classical information without performing a measurment.