LEDs that create entangled pairs!


Well! This is just cool on so many levels. A team of optical-engineering types have found a way to create a specialized LED (light emitting diode) that will create a stream of entangled state photons on demand.

From the report on the Discovery Blog:

“Entangled photons have previously been made using a crystal to split laser light into photon pairs. The trouble with such ‘parametric down conversion’ is its unpredictable nature. ‘Sometimes you get two pairs of photons, sometimes one, sometimes zero,’ says Stephenson [sic]. ‘That’s not exactly reliable if you want an error-free quantum computer’ [New Scientist].

The team’s device, which produces these particles just in pairs, is a indium arsenide quantum dot connected to a little LED. (A quantum dot is semiconductor that measures only nanometers in size—small enough that weird quantum behaviors arise.)

When the researchers supply the LED with electric current, two electrons hop into two positively charged ‘holes’ in the quantum dot’s lattice, releasing energy in the form of a photon pair. Crucially, the nature of this process means that the polarization of one generated photon is determined by the other, so the pair is entangled [Nature].”

Read the full article here.

It’s a small output device right now, and it’s not commercially available, but when it is, it means that one of the key promises of quantum computing – impossible to intercept communications – will be much closer to reality.

And it’s just fascinating to me that this will represent another macroscopic use-case of a quantum phenomenon. (Transistors are another.) The basic premises of classical and relativistic physics say this is impossible. And yet they not only exist, in the case of solid-state transistors, they make it possible for you to read these words right now.

In physics we always expect that if you want to find new science, you have to start by re-examining the basic premises of the old science. Topple an axiom and you’re likely to get yourself to something interesting very quickly. (Like what Riemann did in geometry when he wondered what would happen in a space in which parallel lines actually did eventually meet…)

Entanglement, with the support of the Bell Thm that this is fundamental to nature, seems to me to be another one of the axiom toppling mechanisms.

The Author

Episcopal bishop, dad, astronomer, erstwhile dancer...